Study of the effect of superabsorbent polymers on water...

Núria Roigé Montornés

retention capability and bio-receptivity of mortarsStudy of the effect of superabsorbent polymers on water

Academic year 2015-2016Faculty of Engineering and ArchitectureChair: Prof. dr. ir. Luc TaerweDepartment of Structural Engineering

Inkomende Gast- en ExchangestudentenMaster's dissertation submitted in order to obtain the academic degree of

(University College of London)Counsellors: Dr. ir. Didier Snoeck, Brenda Debbaut, Dr. sandra manso blanco

Politècnica de Catalunya, Barcelona, Spanje)Supervisors: Prof. dr. Nele De Belie, Prof. Antonio Aguado de Cea (Universitat

A la padrina,

no deixis mai de brillar no ens deixis mai de guiar.

“Live as if you were to die tomorrow.

Learn as if you were to live forever”

― Mahatma Gandhi―

http://www.goodreads.com/author/show/182994.Walter_Bagehot

PERMISSION FOR USE ON LOAN The author gives permission to make this master dissertation available for consultation and to copy parts of this master dissertation for personal use. In all cases of other use, the copyright terms have to be respected, in particular with regards to the obligation to state explicitly the source when quoting results from this mater dissertation.

Ghent, June 2016 Núria Roigé Montornés

Preface i


PREFACE

I would like to thank Nele De Belie for give me the opportunity to work in the

Laboratory Magnel. Also, I would like to thank Didier Snoeck for his extremely kindness

and for being always ready to help and solve any doubt. In like manner, I would like to

thank Brenda Debbaut for helping me. I would like to thank Jianyun Wang for her patience,

her assistance and for give me the bases to work in the LabMET. I would like to thank to

the Magnel laboratory staff, especially to Dieter. I would like to thank, Jeroen Dils and

Romy for their kind help with the MIP test.

Vull agrair especialment a l’Antonio Aguado, per totes les oportunitats brindades,

l’oportunitat d’elaborar aquesta tesi és un altre exemple, per estar sempre atent i disposat

a ajudar. A la Sandra Manso, per la seva guia a l’inici i sobretot un cop a Ghent per haver

resolt tots els dubtes. Agrair a l’empresa Escofet 1886 S.A. per la seva col·laboració en la

part experimental. Igualment, agrair al personal del laboratori, en especial al Camilo i al

Robert per ajudar-me amb tot el que vaig necessitar.

Als meus pares perquè gràcies a ells sóc qui sóc i he arribat fins aquí. Per saber

estar allí on havien d’estar en cada moment i fer-ho tot més fàcil. En especial al Quim, per

demostrar-me mil i un cops que tot és possible, no es pot tenir més sort. Als meus avis, que

a la seva manera també han ajudat.

ii Preface

Study of the effect of SAPs on water retention capability and bio-receptivity of mortars

Abstract iii


Study of the effect of superabsorbent polymers on water retention capability and bio-receptivity of mortars Núria Roigé Montornés

Supervisor: Prof. dr. Nele De Belie, Prof. dr. Antonio Aguado de Cea

Counsellors: Dr. ir. Didier Snoeck, Brenda Debbaut, Dr. Sandra Manso Blanco

Master’s dissertation submitted in order to obtain the academic degree of

Master in Civil Engineering, Construction Design

Academic year 2015-2016

ABSTRACT

The evolution of the rural areas to urban cities had a negative impact in the green areas

available. The lack of space in the cities and the necessity of introducing green areas made

green walls, one of the important alternatives to introduce green areas in highly urbanized

cities. Green concrete walls should be an important alternative to obtain the benefits of

green walls and to reduce the visual impact of hard surfaces, since cementitious materials

are used for construction more and more. Despite this, cementitious materials are not the

best substrate for plants. On the contrary, diverse microbial communities composed of

bacteria, cyan bacteria, algae, fungi and lichens shows clear aptitude to colonize these

materials.

With the aim of increasing the features that improve the colonization of cementitious

materials, superabsorbent polymers were used in this study. For this reason, the main

characteristics of different SAPs were defined and different amounts of SAPs in mortar

mixtures were studied followed by the evaluation of their absorbency capacity.

With the most suitable specimens obtained in the above-mentioned experimental

program, other specimens were manufactured with the aim of studying the bio-receptivity

under laboratory conditions. During this process, relevant parameters for the colonization

such as porosity were defined in detail.

At the end of the study, some conclusions as well as further perspectives of research are

presented. From all the results, the main conclusion is that the most suitable specimen to

be colonized is with superabsorbent polymer, using the one that produces more abundant

and well distributed porosity around the surface.

Keywords – bio-receptivity, superabsorbent polymers, chlorella vulgaris, green walls

iv Abstract


Extended abstract v


Study of the effect of superabsorbent polymers on

water retention capability and bio-receptivity of

mortars


Supervisor(s): Prof. dr. Nele De Belie, Prof. dr. Antonio Aguado de Cea, dr. ir. Didier Snoeck, Brenda Debbaut, dr. Sandra Manso Blanco

1

Abstract – The evolution of the rural areas to urban cities had

a negative impact in the green areas available. The lack of space

in the cities and the necessity of introducing green areas made

the green walls, especially green concrete walls, one of the

important alternatives to introduce green areas in highly

urbanized cities. With this purpose, the use of superabsorbent

polymers in mortars with the aim of improving the water

retention capability and the bio-receptivity of this material was

studied. From the results, the most suitable specimen to be

colonized is with superabsorbent polymer, using the one that

produces more abundant and well distributed porosity around

the surface.

Keywords – bio-receptivity, superabsorbent polymers, chlorella

vulgaris

I. INTRODUCTION

Green areas are the ecological measure to combat the

problems of hard surfaces. As the WHO pointed out, people

need between 10 and 15 m2 of green spaces per capita.

Besides the health reasons there are more reasons for which

the green areas are important: such as improvement of the air

quality, moderation of the Urban Heat Island effect and

benefits in terms of energy efficiency and noise attenuation

are straightforward examples.

Green concrete walls should be an important alternative to

obtain the benefits of the green walls and to reduce the visual

impact of the hard surfaces, since cementitious materials are

used for construction more and more. Despite this, cementitious materials are not the best substrate for plants. On

the contrary, diverse microbial communities composed of

bacteria, cyan bacteria, algae, fungi and lichens shows clear

aptitude to colonize these materials. Following the research of

Manso et al. 2014 and with the aim of increasing the features

that improve the colonization of the cementitious materials,

several mixtures containing superabsorbent polymers were

studied.

II. MATERIALS AND METHODS

A. Materials

Three types of SAPs from the company BASF and a SAP

from the University of Ghent were used in the study. From the

Magnel Laboratory for Concrete Research, Faculty of Engineering and

Architecture, Ghent University (UGent), Ghent, Belgium.

SAPs provided by the company BASF only one was

commercial and the other two are under experimental phase. The SAPs are: recycled SAP untreated (SAP_1), recycled

SAP treated (SAP_2), Virgin (SAP_3) and TerraCottem

Universal (SAP_4).

The mortar pastes were mixed following the standard UNE-

EN 196-1. In the first part of the experimental program, the

mixtures were composed of Portland cement (CEM I 52.5 R)

(450 g), silica sand (1350 g) and water (225 g). Additionally

the specimens with SAP contained different amount of SAP

expressed as mass% (m%) of cement weight and additional

water (as shown in Table II.1). The additional water was

defined based on different consistency tests until the expected consistency was reached. This amount served for the loss in

workability and for internal curing of the specimens.

Table II. 1. Composition of the mortar mixtures

Code Cement

[g]

Sand

[g]

Water

[g]

SAP

[g]

Additional

water [g]

REF

225 1350 450

- -

SAP_1 (0.5 m%)

2.25

37.5

SAP_2 (0.5 m%) 37.5

SAP_3 (0.5 m%) 25.0

SAP_4 (0.5 m%) 52.5

SAP_1 (1 m%)

4.50

75.0

SAP_2 (1 m%) 75.0

SAP_3 (1 m%) 50.0

SAP_4 (1 m%) 105.0

SAP_1 (4 m%)

18.00

300.0

SAP_2 (4 m%) 300.0

SAP_3 (4 m%) 200.0

SAP_4 (4 m%) 420.0

SAP_1 (10 m%)

45.00

750.0

SAP_2 (10 m%) 750.0

SAP_3 (10 m%) 500.0

SAP_4 (10 m%) 1050.0

Subsequently, a second set of specimens for the bio-

receptivity experimental program was manufactured. In this

case, the selected SAPs were SAP_3 and SAP_4 and the m%

of SAP was 4 m%. Two different mixtures were used, the

main differences in dosage apart from the quantities described

vi Extended abstract


in Table II.2 was the type of sand. In this case, the code was

change to make it shorter, using the initial of the commercial

name of the SAP and the index 1 and 2 depending on the

dosage used, the reference specimens having the initial C

before the index.

It should be noted that the first specimens were

prismatic samples of 40x40x160 mm3 whereas, the second

plates of 80x80x20 mm3, with the purpose of studying the

bio-receptivity. For this, the specimens should be studied with

the algae fouling test and the set-up was designed for

specimens with this shape. Additionally, after the curing the

second set of specimens was carbonated during 30 days in a

carbonation chamber of CO2 with a concentration of 10%

CO2. After the carbonation period, the pH of the specimens

presented in Table II.2 was checked, as a result below 9 is

necessary for the bio-receptivity test. However, the specimens

were fully carbonated.

Table II.2. Dosage of the specimens to study the bio-

receptivity

Code Cement

[kg]

Sand

[kg]

Water

[kg]

SAP

[kg]

Additional

water [kg]

REF_NORM

(C1)

12.3 36.9

(standard) 8.2

- -

SAP_3_NORM

(V1) 0.5 4.0

SAP_4_NORM

(T1)

REF_PORO

(C2)

8.9 35.9

(0-5mm) 6.0

- -

SAP_3_ PORO

(V2) 0.4 3.0

SAP_4_ PORO

(T2)

B. Absorption kinetics of the SAPs

To determine the absorption kinetics of the studied SAPs

the filtration test was used. The swelling capacity was

calculated from the volume increase between the vacuum-

dried state and the saturated state. The fluid was added to

vacuum-dried SAP particles and the whole was filtrated after

24 hours. Several different fluids were used, demineralised

water, artificial seawater, sulphate solution and cement slurry

filtrate, since they can interact with the structure during its

lifetime (Snoeck et al., 2012).

C. Kinetics behaviour and swelling time of SAPs

The swelling time was determined using the vortex test. The

test consists of adding 100 g of demineralised water and an

amount of SAP to a beaker and using a magnetic stirrer (400

rpm) a vortex was made. The amount of SAPs added is the

necessary amount to absorb 100 g of demineralised water and

is determined from the results obtained in the filtration test.

The time was recorded until the vortex disappeared and this time served as the swelling time.

D. Interaction superabsorbent-mortar

The study of the interaction superabsorbent-mortar was

performed with the specimens presented in Table II.1. The

absorption and desorption capacity was studied after 28 days

of curing. With this purpose, the samples were dried in an

oven (T = 50 °C) during 144 hours, weighing the specimens at

time 0h, 72h and 144h. After the drying, the specimens were

immersed in a tank of water during 48 hours, and at time 0h,

24h and 48h were weighed.

The weight of the specimens during the immersion period

was performed in two different ways: submerged weight and

removing the specimens from the water and drying the surface. With these values, the amount of water loss and water

absorption as well as the volume of voids could be

determined.

E. Dynamic vapour sorption (DVS)

The DVS test was performed to samples with a size of 500-

1000 μm after being pre-dried one week with vacuum-drying

(20±2 °C) at 0.1 bar.

The Dynamic Vapour Sorption apparatus used was from

Surface Measurement System, London, UK. The temperature

was set at 20°C and the mass criterion to proceed to the next

RH step was dm/dt < 0.002 wt·%/min. Dried cement pastes

were first conditioned at 0% RH inside the DVS equipment

followed by an absorption-desorption cycle (Snoeck et al.,

2014). The RH level at which samples (5-10 mg) was

subsequently equilibrated included 0-2-5-10-20-30-40-50-60-

70-80-90-95-98% RH.

F. Mercury intrusion porosimetry (MIP)

To prepare the samples for the MIP test they were cut and

dried using the freeze-drying method, first the samples were

dried in liquid nitrogen and placed in a freeze-dryer

instantaneously for 3 weeks (Mini Lyotrap freeze dryer, LTE

Scientific). The test consisted in weighting and placing the dried

samples into a chamber (dilatometer). Then, the air in the

chamber was evacuated and the mercury filled up the camber.

As the applied pressure increased, mercury is forced to

intrude into the samples gradually. The mercury intrusion

volumes and the corresponding applied pressures were

recorded at every pressure step. These values provided the

basic data to analyse the pores structure under the assumption

that pores are cylindrical, entirely and equally accessible to

mercury so that the pressure can be converted the pore

diameter.

G. Air-void analysis

The rapid air-void test was performed on the surface of the

specimens in order to determine the large range of pores.

These surface pores are caused by the SAPs and they air

voids.

For this test, the surfaces of the specimens (80x80 mm2) were polished and put in an oven at 40 °C to let them dry.

Afterwards, the specimens were coloured black by gently

dragging a broad tipped marker. Then, were dried again in the

oven and subsequently dry powder (BaSO4) was sprinkled

over the surface and fills the voids by tamping a hard rubber

stopped over the surface of the specimen. Finally, the excess

of powder was removed by means of a spatula.

The test was performed by means of Rapid Air 457, which

is an automated system for analysis of air void content

according to EN 480. The analysis was performed using 3

Extended abstract vii


transverse lines per frame and the transversal length was 2400

mm. The ratio paste volume to the total volume was

calculated and inserted into the analyser program.

III. RESULTS

A. SAPs characterization

Table III.1. displays the average of the results (n=3) with

the standard deviation of the filtration test with the different

fluids and the swelling time until full saturation.

The results show similar behaviour for demineralised water

and cement filtration solution for SAPs 2, 3 and SAPs 1, 4.

The absorption in cement slurry filtrate is lower than in

demineralised water, because of the charge screening effect

resulting from the cations K+, Na+, Mg2+ and Ca2+ in the filtrate and the strong complexation.

Table III.1. Absorption of SAPs [g fluid/g SAP] in different

solutions and the swelling time [s]

SAP_1 SAP_2 SAP_3 SAP_4

Δm/m

demineralised

water

259.65±11.85 322.99±21.12 291.75±12.44 240.30±95.77

Δm/m seawater 20.59±0.83 18.70±1.64 20.15±0.21 17.03±5.23

Δm/m Na2SO4 32.98±1.25 28.66±2.17 31.88±0.84 25.53±4.22

Δm/m cement

filtrate solution 24.06±1.68 12.16±0.99 11.83±0.86 19.27±5.39

Swelling time [s] 131.15±13.75 223.16±10.02 193.12±9.53 793.54±282.19

B. Mortar characterization

Studying the different trends of the absorption and

desorption of all the samples presented in Table II.1, the most

appropriate behaviour was observed with an amount of 4 m%

of SAPs, the absorption results over time are presented in

Figure III.1.

Figure III.1. Amount of absorbed water due to the immersion with 4 m% of SAP

Two main behaviours are observed in Figure III.1, larger

absorbency followed by SAP 1 and 4, and a second behaviour

with less absorbency followed by SAP 2 and 3.

C. Bio-receptivity specimens characterization

The porosity is an important parameter for the bio-

receptivity. For this reason, specimens presented in Table II.2 were subjected to different tests in order to characterize the

porosity at different levels. DVS and MIP tests were

performed to define the microstructure whereas, the

macrostructure was defined based on the larger pore sized

obtained with MIP and the Air-void test.

Related to the microstructure, the denser specimens were

those that are defined in Table II.2 with an index 2, giving a

higher effective cement-to-water ratio.

However, the same specimens present higher amount of

macropores, produced by the different sand used with a large

grain size. The denser specimens related to the macropores were, as was expected, C1 and C2, the references without

SAP.

IV. BIO-RECEPTIVITY

A. Materials and methods

The accelerated algae fouling test was developed by De

Muynck et al., (2009), consists in a modular test set-up allowing to evaluate simultaneously different materials

towards algal fouling. The test consisted of inclined (45º) and

independent PVC compartments where the samples are

placed. Then, the test was composed by two periods that

started every 12 hours and ran for 90 minutes. Every day there

was a 12 hours day and night regime, which started

simultaneously with the 90 minutes run-off periods (De

Muynck et al., 2009). During the day regime, light was

provided by means of Sylvania Grolux 30 W lamps. The

temperature and relative humidity ranged 25°C (day) – 22°C

(night) and 82 % (day) – 90 % (night). The test was carried out with the algae specie Chlorella vulgaris fo. viridis.

obtained from the CCAP Scottish Marine Institute, Oban, UK.

To quantify and analyse the evolution of the fouling some

methods proposed in the literature were used. Since

colorimetric measurements and image analysis have been

corroborated as good methods by (De Muynck et al., 2009;

Manso et al., 2014; among others), those were studied. The

colorimetric measurements were performed by means of an

X-Rite SP60 colorimeter, and analysed with the equations (1)

to (4). Due to the fact that the colorimetric measurements are

sensitive to the moisture content, the specimens were studied

10 hours after the irrigation occurred, ensuring the same moisture content.

(1)

(2)

(3)

(4)

For the image analysis the specimens were scanned with a

Canon Scan 3000F scanner and afterwards the image analysis

was done with the ImageJ software.

0

40

80

120

160

200

0 8 16 24 32 40 48

Weig

ht

(g)

Time (h)

REF SAP_1 (4 m%)

SAP_2 (4 m%) SAP_3 (4 m%)

SAP_4 (4 m%)

viii Extended abstract


B. Colorimetric results

The colorimetric measurements were done each week and at

each specimen 4 measurements were performed near each edge of the plate. Therefore the results presented are the

average of twelve measurements (n=3). The reflectance

curves are presented in Figure IV.1 displaying the results of

the week 10 (end of the test).

As could be observed in Figure IV.1, the larger percentage

of fouling intensity (FI) - meaning large drops between

wavelength 670 nm and 700 nm - are seen in the specimens

V2 and C2.

Figure IV.1. Reflectance curves for all the specimens

C. Image analysis results

With the image analysis the evolution of visual appearance

of the specimens is observed, and by using the ImageJ

software, the percentage of fouling area was determined.

Figure IV.2, presents the evolution of the fouling each two

weeks. Coinciding with the results obtained in the

colorimetric analysis the specimens with larger percentage of

fouling area are C2 and V2. From the visual comparison,

different thickness of fouling was observed being more thin in the specimen C2 and more dense in the surface of V2.

Week 1 2 4 6 8 10

C1

C2

T1

T2

V1

V2

Figure IV.2. Evolution of visual appearance of the specimens

subjected to accelerated algal fouling test

V. CONCLUSIONS

The porosity generated by the SAPs has a large effect in the

bio-receptivity of the specimens. As there are more pores and

they are more equally distributed around the surface, a higher

degree of fouling is achieved. As a consequence, the specimen with the superabsorbent polymer Virgin and the more porous

dosage (V2) is the most suitable specimens to be colonized by

the algae Chlorella vulgaris under laboratory conditions.

VI. ACKNOWLEDGEMENTS

I would like to thank all the people that were involved in

this dissertation. Especially, the people that help me during

the experimental program that was carried on in three different laboratories and one company: the Laboratory of

Structure Technology Luis Agulló (UPC), the company

Escofet 1886 S.A., the Magnel Laboratory for Concrete

Research (UGent) and the Laboratory of Microbial Ecology

and Technology, LabMET (UGent).

VII. REFERENCING

[1] Manso S., De Muynck W., Segura I., Aguado A., Steppe K., Boon N.

and De Belie N. “Bioreceptivity evaluation of cementitious materials

designed to simulate biological growth”. Science of the Total

Environment 481, 232–241, 2014.

[2] Snoeck D., Steuperaert S., Van Tittelboom K., Dubruel P. and De

Belie N. “Visualization of water penetration in cementitious materials

with superabsorbent polymers by means of neutron radiography”.

Cement and Concrete Research, 42, 1113–1121, 2012.

[3] Snoeck D., Velasco L.F., Mignon A., Van Vlierberghe S., Dubruel P.,

Lodewyckx P. And De Belie N. “The influence of different drying

techniques on the water sorption properties of cement-based

materials”. Cement and Concrete Research 64, 54–62, 2014.

[4] De Muynck W., Maury Ramirez A., De Belie N. and Verstraete W.

“Evaluation of strategies to prevent algal fouling on white architectural

and cellular concrete”. International Biodeterioration &

Biodegradation, 63, 2009.

0

5

10

15

20

400 500 600 700

Re

fle

cta

nce

[%]

Wavelength [nm]

C1 V1 T1 C2 V2 T2

Table of contents ix


TABLE OF CONTENTS

CHAPTER 1. INTRODUCTION AND OBJECTIVES...................................................................... 1

1.1. Scope of the research ................................................................................................... 1

1.2. Objectives ...................................................................................................................... 2

1.3. Methodology ................................................................................................................. 2

CHAPTER 2. STATE OF THE ART ................................................................................................. 5

2.1. Introduction .................................................................................................................. 5

2.2. Green walls .................................................................................................................... 6

2.3. Bio-receptivity .............................................................................................................. 7

2.3.1 Material properties related to bio-receptivity ......................................................... 9

2.3.2 Biomass quantification techniques ......................................................................... 10

2.4. Superabsorbent Polymers (SAPs) ........................................................................... 12

2.4.1 Classification ............................................................................................................... 13

2.4.2 History ......................................................................................................................... 13

2.4.3 Production ................................................................................................................... 14

2.4.4 Characterization ......................................................................................................... 16

2.5. Cement-Based systems containing superabsorbent polymers ........................... 19

2.5.1 Absorption................................................................................................................... 19

2.5.2 Desorption ................................................................................................................... 20

2.5.3 Workability of concrete and mortar containing SAP ............................................ 21

2.6. Construction applications of SAP in concrete ........................................................ 22

2.6.1 Improvement on concrete properties ..................................................................... 22

2.6.2 Potential applications ................................................................................................ 22

CHAPTER 3. MATERIALS AND METHODS ............................................................................... 25

3.1. Introduction ................................................................................................................ 25

3.2. Materials ...................................................................................................................... 25

3.2.1 Recycled SAP untreated ............................................................................................ 26

3.2.2 Recycled SAP treated ................................................................................................. 27

3.2.3 Virgin ............................................................................................................................ 27

3.2.4 TerraCottem Universal .............................................................................................. 28

3.2.5 Microscopic analysis .................................................................................................. 29

3.3. Absorption kinetics .................................................................................................... 32

x Table of contents


3.3.1 Systematic procedure ................................................................................................ 32

3.3.2 Filtration method ....................................................................................................... 33

3.4. Kinetic behaviour and swelling time determination ............................................ 33

3.5. Interaction with mortar ............................................................................................ 34

3.5.1 Absorption and desorption test ............................................................................... 36

3.5.2 Void volume ................................................................................................................ 37

3.6. Specimens for accelerated algal test ....................................................................... 38

3.7. Dynamic vapour sorption (DVS) .............................................................................. 40

3.8. Mercury intrusion porosimetry (MIP) .................................................................... 41

3.9. Air-Void analysis ........................................................................................................ 42

CHAPTER 4. RESULTS OF SUPERABSORBENT AND MORTAR CHARACTERIZATION .. 45

4.1. Introduction ................................................................................................................ 45

4.2. SAPs Characterization ............................................................................................... 45

4.3. Mortar Characterization............................................................................................ 47

4.3.1 Absorption and desorption test ............................................................................... 48

4.3.2 Study the percentage of voids .................................................................................. 52

4.3.3 Conclusions ................................................................................................................. 53

4.4. Characterization of the bio-receptivity specimens ............................................... 53

4.4.1 Dynamics water vapour sorption isotherms ......................................................... 55

4.4.2 Amount and distribution of pores calculated by means of the BJH and DR

methods .................................................................................................................................... 56

4.4.3 Mercury intrusion porosimetry ............................................................................... 58

4.4.4 Air-void analysis ......................................................................................................... 59

CHAPTER 5. BIO-RECEPTIVITY EVALUATION UNDER LABORATORY CONDITIONS ... 63

5.1. Introduction ................................................................................................................ 63

5.2. Mortar specimens ...................................................................................................... 64

5.3. Accelerated algae fouling test .................................................................................. 64

5.4. Evolution and quantification of biofouling ............................................................ 68

5.5. Results of accelerated algae fouling test ................................................................. 71

5.5.1 Colorimetric measurements ..................................................................................... 71

5.5.2 Image analysis ............................................................................................................ 77

5.5.3 Microscopic analysis .................................................................................................. 78

5.6. Study under special conditions of accelerated algae fouling test ....................... 80

Table of contents xi


5.6.1 Results of the special accelerated algae fouling test ............................................. 80

CHAPTER 6. CONCLUSIONS AND FUTURE PRESPECTIVES ................................................. 85

6.1. General conclusions ................................................................................................... 85

6.2. Specific conclusions ................................................................................................... 86

6.3. Further perspectives ................................................................................................. 88

REFERENCES................................................................................................................................... 89

APPENDIX A .................................................................................................................................... 97

1. Introduction ................................................................................................................ 97

2. Consistency test .......................................................................................................... 97

2.1. SAP_1.. .......................................................................................................................... 97

2.2. SAP_2.. .......................................................................................................................... 98

2.3. SAP_3.. .......................................................................................................................... 99

2.4. SAP_4.. ....................................................................................................................... 100

xii Table of contents


List of figures xiii


LIST OF FIGURES

Figure 1.1. Organizing outline ................................................................................................................................. 4

Figure 2.1. Classification of green walls taking into account the construction

characteristics.. ............................................................................................................................................................... 6

Figure 2.2. Indirect green facade ........................................................................................................................... 7

Figure 2.3. Continuous living wall system, Caixa Forum, Madrid ......................................................... 7

Figure 2.4.Extensive lichen colonization. Palácio Nacional de Queluz, Portugal.......................... 8

Figure 2.5. Superabsorbent polymers are substances which can absorb many times their

own weight of liquids by forming a gel (left: dry particle; right: swollen particle) ................. 12

Figure 2.6. SAP based on polyacrylic acid: swelling mechanism (Mechtcherine et al.,

2012)................... ............................................................................................................................................................. 12

Figure 2.7.Schematic diagram of: a) bulk polymerization and b) solution polymerization 15

Figure 2.8.Schematic diagram of: a) suspension polymerization and b) emulsion

polymerization ............................................................................................................................................................. 15

Figure 2.9. a) Typical AUL tester picture; b) description of the various parts18 (Zohuriaan-

Mehr et al., 2008) ........................................................................................................................................................ 18

Figure 2.10. Schematic evolution in time of the SAP in a cementitious material. a) Initial

condition, with homogeneous dispersion of cement particles, water, SAP and aggregates;

b) The SAP has reached final absorption; c) The water has been transported into the

cementitious matrix and an almost empty pore remains. (Mechtcherine et al., 2012) ......... 20

Figure 3.1. Outline of the experimental program....................................................................................... 26

Figure 3.2. SAP 1 – Recycled SAP untreated (BASF)................................................................................. 27

Figure 3.3. SAP 2 – Recycled SAP treated (BASF) ...................................................................................... 27

Figure 3.4. SAP 3 – Virgin (BASF) ....................................................................................................................... 28

Figure 3.5. SAP 4 – TerraCottem Universal (UGent)................................................................................. 29

Figure 3.6. SAP 1 – Microscopic analysis ........................................................................................................ 30




Figure 3.10. a) 1g of dry SAP; b) 1g of SAP after hydration ................................................................. 32

Figure 3.11. SAP filtration after 24 hours ...................................................................................................... 33

Figure 3.12. Vortex test............................................................................................................................................ 34

Figure 3.13. Excess water in the mortars with 10% of SAP ................................................................. 36

Figure 3.14. Specimens during the immersion process .......................................................................... 37

Figure 3.15. Weighing scale to obtain the submerged weight ............................................................ 37

Figure 3.16. Polyurethane moulds (80x80x20 mm3)............................................................................... 39

xiv List of figures


Figure 3.17. Samples after the phenolphthalein test fully carbonated ........................................... 40

Figure 3.18. a) Schematic overview of the dynamic vapour sorption (DVS) methodology; b)

the used equipment, where samples stored in the presence of soda lime are put into the

sample container and the whole is put in the DVS equipment.(Snoeck et al., 2014) .............. 41

Figure 3.19. a) Particles of 500 μm; b) Drying of the sample............................................................... 41

Figure 3.20. Equipment used for carried out the MIP test (left: lower pressure; right:

higher pressure) .......................................................................................................................................................... 42

Figure 3.21. Final result of the surface (left: contact with mould and right: not contact with

mould).......... .................................................................................................................................................................... 43

Figure 3.22. Air void analyser, Rapid Air 457 .............................................................................................. 44

Figure 4.1. Absorption of SAPs with different fluids a) demineralised water, b) seawater, c)

Sodium sulphate and d) cement filtrate solution ....................................................................................... 46

Figure 4.2. Dimensionless swelling factor, f [-] ........................................................................................... 47

Figure 4.3. Amount of evaporated water due to the drying in different SAPs:50a) SAP 1, b)

SAP 2, c) SAP 3 and d) SAP 4 ................................................................................................................................. 50

Figure 4.4. Amount of absorbed water due to the immersion in different SAPs: a) SAP 1, b)

SAP 2, c) SAP 3 and d) SAP 4 ................................................................................................................................. 51

Figure 4.5. Amount of absorbed water due to the immersion with 4 m% of SAP .................... 52

Figure 4.6. Percentage of voids in different SAPs ...................................................................................... 53

Table 4.6. Classification of pores and features in concrete (Mindess et al., 1996) ................... 55

Figure 4.7. a) DVS change in mass at each RH and b) isotherm plot of the specimen V1 .... 55

Figure 4.8. Dynamic water vapour sorption results. ................................................................................ 56

Figure 4.9. Calculated microstructure with the BJH method. .............................................................. 57

Figure 4.10. Cumulative intrusion volume [mm3/g]vs. Pore diameter curves ........................... 58

Figure 4.11. Incremental intrusion vs. Pore diameter curves ............................................................. 59

Figure 4.12. Percentage of pores of the following ranges: > 10 μm; 1 – 10 μm; 0.1 – 1 μm; <

0.1 μm........... .................................................................................................................................................................... 59

Figure 4.13. Measurements of mould face and air face of: a) Air content [%] and b) spacing

factor [mm] .................................................................................................................................................................... 60

Figure 4.14. Pore size (left: mould face and right: air face) .................................................................. 61

Figure 5.1. Schematic setup used for the accelerated algal fouling test ......................................... 64

Figure 5.2. Accelerated algal fouling test........................................................................................................ 65

Figure 5.3. a) 15.0 g of Bacteriological Agar; b) First growing batch .............................................. 65

Figure 5.4. One week old culture and new culture .................................................................................... 65

Figure 5.5. Light microscope Zeiss Axioskop II plus................................................................................. 67

Figure 5.6. Neubauer chamber ............................................................................................................................ 67

Figure 5.7. Count in a Neubauer chamber big square.............................................................................. 68

List of figures xv


Figure 5.8. a) Three-dimensional CIELAB colour space (Li et al., 2005); b) X-Rite SP60

colorimeter ..................................................................................................................................................................... 68

Figure 5.9. Absorption spectra of Chlorophyll a, b and carotenoids (UIC, 2014)...................... 69

Figure 5.10. Correlation between a) the real sample the b) threshold operation on the a*

axis and c) threshold operation on the b* axis. ........................................................................................... 70

Figure 5.11. Leica microscope .............................................................................................................................. 70

Figure 5.12. Heterogeneity between replicates of the same specimen .......................................... 71

Figure 5.13. Reflectance of each replicate as well as the average of them ................................... 72

Figure 5.14. Heterogeneity in fouling of a replicate: a) sample T2 after 8 weeks b)

reflectance.. .................................................................................................................................................................... 72

Figure 5.15. Reflectance curves of specimens: a) C1; b) C2; c) V1; d) V2; e) T1 and f) T2 ... 73

Figure 5.16. Reflectance curves for all the specimens: a) week 0; b) week 6; c) week 8 and

d) week 10.... .................................................................................................................................................................. 74

Figure 5.17. Representation of the fouling intensity [%]....................................................................... 76

Figure 5.18. Evolution over time of fouling intensity [%] for all the specimens ....................... 76

Figure 5.19. Evolution of visual appearance of the specimens subjected to accelerated algal

fouling test...................................................................................................................................................................... 77

Figure 5.20. Evolution over time of the fouled area [%] for all the specimens .......................... 78

Figure 5.21. Specimen V2: a) after 3 weeks, b) after 7 weeks and c) after 10 weeks ............. 79

Figure 5.22. Pore of specimen T2: a) after 3 weeks, b) after 7 weeks and c) after 10

weeks............ .................................................................................................................................................................... 79

Figure 5.23. Pore of specimen V2: a) 2 mm view and b) 500 μm view........................................... 79

Figure 5.24. Reflectance curves for all the specimens, special conditions: a) week 0; b)

week 2; c) week 4 d) week 6, e) week 8 and f) week 10 ........................................................................ 81

Figure 5.25. Evolution over the time of the fouling intensity [%], special conditions ............ 82

Figure 5.26. Visual appearance of the specimens after 10 weeks in special conditions (first

line: C1, V1, T1; second line: C2, V2, T2) ......................................................................................................... 83

Figure A.1. Consistency test before and after the blows for SAP_1 .................................................. 98



Figure A.4. Consistency test before and after the blows for SAP_4 ............................................... 100

xvi List of figures


List of tables xvii


LIST OF TABLES

Table 1.1. Specific objectives ................................................................................................................................... 3

Table 2.1. Stone characteristics appraised by several authors (Miller et al., 2012) ................ 10

Table 3.1. Average of the diameter [mm] ....................................................................................................... 29

Table 3.2. Amount of water added to 1g of SAP .......................................................................................... 32

Table 3.3. Added water until the expected consistency ......................................................................... 34

Table 3.4. Composition of the mortar mixtures .......................................................................................... 35

Table 3.5. Dosage of the specimens to study the bio-receptivity ....................................................... 39

Table 3.6. Calculated volume ratio of the paste to the total volume ................................................ 44

Table 4.1. Absorption of SAPs [g fluid/g SAP] in different solutions and the swelling time

[s]................... ..................................................................................................................................................................... 46

Table 4.2. Dimensionless swelling factor, f [-] ............................................................................................. 47

Table 4.3. Weight values at each step [g] ....................................................................................................... 48

Table 4.4. Amount of evaporated and absorbed water [g].................................................................... 49

Table 4.5. Corresponding water-to-cement ratios (additional, total and effective) of the

specimens... .................................................................................................................................................................... 54

Table 4.6. Classification of pores and features in concrete (Mindess et al., 1996) ................... 55

Table 4.7. C-S-H amount and comparison between the textural parameters calculated by

water sorption (~20 ), specific surface area SBET, mesopore and micropore volumes...... 57

Table 4.8. Air content [%] and spacing factor [mm] given by Rapid Air test .............................. 60

Table 5.1. Selected specimens to study the bio-receptivity .................................................................. 64

Table 5.2. Stock solution ......................................................................................................................................... 66

Table 5.3. Final medium solution ....................................................................................................................... 66

Table 5.4. Colorimetric measurements ........................................................................................................... 75

Table 5.5. Colorimetric measurements, special conditions .................................................................. 82

Table A.1. Added water until the expected consistency for SAP_1 ................................................... 97



Table A.4. Added water until the expected consistency for SAP_4 ................................................ 100

xviii List of tables


Symbols and nomenclature xix


SYMBOLS

Symbols Unit Explanations

a* - green-red light component

At g weight of water-absorbed polymer at time t

b* - blue-yellow light component

B g weight of the sieve

D m equivalent pore diameter

E N buoyant force of a given body

f - swelling factor (ionic sensitivity)

m/s2 acceleration due to gravity

L* - lightness factor

n - number of specimens

Pa applied pressure

- swelling capacity

SR (g/g s) swelling rate

St g/g swelling at time t

t s time

tvd s time of disappearance of vortex

m3 volume of holes

m3 geometrical volume of the specimen

m3 volume of the displaced fluid

m3 volume of the specimen mass

kg dry weight of the specimen

kg submerged weight of the specimen

W0 g weight of the initial sample

W1 g weight of the bag stage 1

W2 g weight of the bag stage 2

W3 g weight of sap sample

W4 g weight of the fluid

W5 g weight of the vacuum-dried sap particles

W6 g weight of the filtrated fluid after 1 day

Δa* - green-red light colour difference

Δb* - blue-yellow light colour difference

xx Symbols and nomenclature


ΔC* - chromatic variations

ΔE* - total colour difference

ΔH* - changes in hue

ΔL* - lightness difference

N/m surface tension of mercury

s-1 shear strain rate

kg/m3 fluid density (water )

Pa yield stress

° contact angle between mercury and the solid surface

Pa s plastic viscosity

Pa shear stress applied to the material

TERMINOLOGY AND NOMENCLATURE

AA: acrylic acid.

AAC: autoclaved aerated concrete.

AM: acrylamide.

AUL: absorbency under load.

BaSO4: barium sulphate

Bio-receptivity: the aptitude of a material to be colonised by one or several group of living

organisms without necessarily affected by chemical, physical, and/or biological

weathering problem.

BJH: Barrett, Joyner and Halenda.

CaCl2: calcium chloride

CaCl2·2H2O: calcium chloride dihydrate

CaCO3: calcium carbonate.

CCAP: culture collection of algae and protozoa

CO2: carbon dioxide

Continuous phase: phase which is not interrupted in space.

Symbols and nomenclature xxi


C-S-H: calcium silicate hydrate.

DR: Dubinin-Radushkevich

DVS: dynamic vapour sorption.

Emulsion polymerization: polymerization whereby monomer(s), initiator, dispersion

medium and possibly colloid stabilizer constitute initially an inhomogeneous system

resulting in particles of colloidal dimensions containing the formed polymer.

FI: fouling intensity

Gel: nonfluid colloidal network or polymer network that is expanded throughout its whole

volume by a fluid.

Hydrogel: gel in which the swelling agent is water.

IC: internal curing

IS: impedance spectroscopy.

K2HPO4·3H2O: potassium hydrogen phosphate trihydrate KH2PO4: potassium dihydrogen phosphate

LWS: living walls systems.

m %: mass percentage of cement.

Macroporous particle: particle containing pores of diameters exceeding about 50 nm.

Mesoporous particle: particle containing pores of diameter between approximately 2 and

50 nm.

MgBr2: magnesium bromide

MgSO4·7H2O: magnesium sulphate heptahydrate

Micelle: particle of colloidal dimensions that exists in equilibrium with the molecules or

ions in solution from which it is formed.

Microporous particle: particle containing pores of diameter not exceeding 2 nm.

MIP: mercury intrusion porosimetry.

Na2SO4: sodium sulphate

xxii Symbols and nomenclature


NaCl: sodium chloride

NaNO3: sodium nitrate

OM: optical microscopy.

RH: relative humidity.

SAP 1: Recycled SAP untreated (company BASF)

SAP 2: Recycled SAP treated (company BASF)

SAP 3: Virgin (company BASF)

SAP 4: TerraCottem Universal (UGent)

SAP: superabsorbent polymer

SBET-values: specific surface area accessible to gas molecules

SEM: scanning electron microscopy.

UCS: unconfined compressive strengths.

UHI: Urban heat island.

w/c: water-to-cement

Introduction and Objectives 1


CHAPTER 1

INTRODUCTION AND OBJECTIVES

1.1. SCOPE OF THE RESEARCH

Over the past several decades, growth has jumped over beyond cities into many

areas that were once rural. Today development is converting farms and forests to other

uses at an increasingly rapid rate. And, too often, this is done without firm land-use plans

in place to guide development, as a result there is an increasing urban sprawl.

According to the World Health Organization (WHO), people need between 10 and

15 m2 of green space per capita, to be distributed in accordance with the population

density in a given area. This means that for every four-storey building with two homes per

floor there should be a green area of at least 22 m2. Obviously, this does not mean that a

green space should be right next to our front door, but the WHO does point out that the

closer, the better. This necessity should awareness the society that during the expansion of

cities, the urban planning should be taking into account space for green areas.

However, when larger cities are constructed and the land has been built up with

people living there, it is not possible to generate more green areas like parks and gardens.

An effective solution to this problem is generating green walls. Fortunately, most of the

small plants, such as mosses, climbers and small bushes, grow readily on walls and steep

slopes.

2 Chapter 1


Apart from the generation of a green area, green walls have other advantages such

as air filter or green lungs, one square meter of such gardens capturing 130 g of dust and

giving off enough oxygen for one person per year. In addition, apart from the health

benefits, they have also financial benefits. They can reduce the amount of energy

necessary for the heating during the winter and for the cooling during the summer.

Moreover, other benefits as the noise attenuation and electromagnetic radiations are

provided by the green walls.

Green concrete walls, proposed by Manso et al. 2014 should be an important

alternative to obtain the benefits of the green walls and to reduce the visual impact of the

hard surfaces, since cementitious materials are used for construction more and more.

Despite this, it is known that cementitious materials are not the best substrate for plants,

contrarily, diverse microbial communities shows clear aptitude to colonize this materials.

Following the same line of investigation, and with the aim of increase the features that

improve the colonization of the cementitious materials the study of this thesis is oriented.

1.2. OBJECTIVES

The aim of this thesis is to improve the water retention on the mortars in order to

increase the bio-receptivity. Superabsorbent polymers (SAPs) are used with the purpose

of improve the water retention, what is expected is that the superabsorbent takes the

water during the wet periods whereas during the driest periods the superabsorbent

provides this reserved water. Taking that into account, some general objectives that

correspond to the main subjects addressed in this study are defined as follows.

Study the different superabsorbent polymers in order to characterise them.

Analyse the kinetics of the water in mortars containing superabsorbent polymers.

Evaluate the bio-receptivity.

In order to achieve the mains goals several specific objectives are set. Table 1.1

shows the main specific goals for each subject treated in the study.

1.3. METHODOLOGY

This thesis is subdivided into six chapters, some references and an appendix as

show in Figure 1.1. The introduction and the main subjects to go through the document in

the first and second chapter are explained. At this point, the characterization of the

materials are presented and different test are realized which are used in order to analyse

the different dosages. At the end, the bio-receptivity study is realized.

In Chapter 1, a brief scope of the research is presented followed by the general and

specific objectives with the methodology to achieve them.

Introduction and Objectives 3


Chapter 2 provides a state of the art of the subject addressed in this thesis, trying

to provide an overview of the main topics of the thesis.

The characterization of the materials used and the methods of the experimental

program were conducted in the Chapter 3.

Chapter 4 presents the results obtained and is the important issue to define the set

of specimens to evaluate by the bio-receptivity test. The main features, such as the

porosity, of this set of specimens is also analysed in this chapter.

Chapter 5 covers several subjects related to the bio-receptivity, the methodology

of the bio-receptivity test used under laboratory conditions followed by the

materials used to perform it. The quantification methods used to evaluate the

degree of fouling were described and subsequently, the results analysed.

Finally, conclusions of the subjects addressed in this thesis and future perspectives

of research of this work are provided in Chapter 6.

Table 1.1. Specific objectives

Goal Specific objective

Superabsorbent polymers

Perform different test in order to define the main characteristics

Compare the different types of superabsorbent polymers

Water kinetics of mortars containing

superabsorbent polymers

Determine the amount of additional water needed to obtain the same workability

Manufacture specimens with different m% (mass-percent of cement weight) of SAP

Perform different test to obtain the capacity of absorb and desorb water

To obtain information about the formed microstructure by means of water vapour sorption and mercury intrusion porosimetry

Bio-receptivity

Evaluate the specimens under laboratory conditions of

colonization

Study the influence of lack of rain during alternate weeks

(rain only the odd weeks)

Define the most appropriate specimens for the colonization

4 Chapter 1


Figure 1.1. Organizing outline

BIO-RECEPTIVITY

CHAPTER 5

(Bio-receptivity evolution

under laboratory conditions)

CHAPTER 1

(Introduction and Objectives)

CHAPTER 2

(State of the art)

CHAPTER 6

(Conclusions)

CHARACTERIZATION

CHAPTER 3

(Materials and Methods)

CHAPTER 4

(Results of SAPs and Mortar

Characterization)

State of the art 5


CHAPTER 2

STATE OF THE ART

2.1. INTRODUCTION

In recent years, there has been a tremendous growth in population and buildings

in cities. The high concentration of hard surfaces produces many environmental issues

such as the urban heat island (UHI) effect. The UHI effect is a phenomenon where air

temperatures in densely built cities are higher than the suburban rural areas. The primary

root of heat island in cities is due to the absorption of solar radiation by mass building

structures, roads and other hard surfaces during day time. The absorbed heat is

subsequently re-radiated to the surroundings and increases ambient temperatures at

night (Wong et al., 2005).

Green areas are the ecological measure to combat the problems of the hard

surfaces. The incoming solar radiation is converted into energy for transpiration and

photosynthesis through any surface planted consequently the sensible heat flux is lower.

During the night, the energy of the outgoing net radiation from a green surface is fed from

the thermal heat flux and the latent heat flux. Therefore, the temperature around the green

area is lower than that around the built environment. Thus, the green areas are playing an

important role in moderating the urban climate during recent years.

The lack of space in the cities and the necessity of introduce green areas made the

green roofs and green walls one way to deal with the reduced space to install parks that

require large surfaces. Improving the air quality of the cities and moderating the Urban

Heat Island (UHI) effect. Apart from this, there is an important benefit in terms of energy

6 Chapter 2


efficiency; the greater insulation offered by them can reduce the amount of energy needed

to moderate the temperature of a building. For example, research published by the

National Research Council of Canada found that an extensive green roof reduced the daily

energy demand for air conditioning in the summer by more than 75% (Liu et al., 2003).

Moreover, there is a reduction of the noise since they have excellent noise attenuation and

a reduction of electromagnetic radiation.

Green walls have a greater potential than green roofs considering that in urban

centres the extent of facade greening can be double the ground footprint of buildings

(Kohler, 2008).

The aim of this chapter is to reviews the different kind of green walls available

nowadays as well as the superabsorbent polymers and its own application in concrete

construction in order to make an overview of the possibilities available.

2.2. Green walls

Due to the fact that green walls are becoming more and more important a recent

development in its technology is happening, for this reason it is important to identify and

classify all existing green walls systems, according to their construction techniques and

main characteristics. In figure 2.1 a classification according to the different existing

systems and their construction characteristics is proposed.

Figure 2.1.Classification of green walls taking into account the construction characteristics

Green facades consist in climbing or hanging plants along the wall. In this case,

the plants grow upwards the vertical surface or downwards depending on the position

and the height of the hanged.

Green facades in turn can be classified as direct or indirect. When the plants are

attached directly to the wall they are called direct green facades and is the traditional

Green walls

Green facades

Living walls

(LWS)

Direct

Indirect

Traditional green facades

Continuous guides

Modular trellis

Continuo

us

Modular

Trays Vessels

Flexible bags

Lightweight screens

Planter tiles

State of the art 7


solution, whereas indirect green facades need an additional supporting structure for

vegetation.

Figure 2.2. Indirect green facade

Living walls systems (LWS) are a new type of green walls and they emerged to

allow the integration of green walls in high buildings. They allow a rapid coverage of large

surfaces and a uniform growth along this surface. In this case, the variety of different

species of plants is possible.

Living walls can be classified as continuous or modular. The continuous consist in

the application of lightweight and permeable screens in which plants are inserted

individually. The modular living walls are based on elements with specific dimension,

which include the growing media where plants can grow. In the case of use the modular

type an additional structure that supports each module is needed.

Figure 2.3. Continuous living wall system, Caixa Forum, Madrid

2.3. BIO-RECEPTIVITY

The term bio-receptivity was defined by Guillitte in 1995 as “the ability of a

material to be colonized by one or several groups of living organisms without necessarily

undergoing and biodeterioration” or “the totality of materials properties that contribute to

the establishment, anchorage and development of fauna and/or flora”. Since the term bio-

8 Chapter 2


receptivity was defined by Guillitte in 1995 a number of studies have addressed this

subject.

Traditionally the materials that was most exposed to this colonization was the

stones since it was the most important material in construction. However, nowadays this

trend has changed and concrete is becoming the most popular material in civil engineering

environment.

It is well known that rocks, either in natural geological outcrops or in buildings and

monuments, are common habitats for a wide variety of microorganisms. Several authors

reported that microorganisms may play an important and substantial role in all rock

alteration processes, inducting aesthetical, physical and chemical changes (Krumbein,

1988; Saiz-Jimenez, 1994; Gorbushina, 2007). In some natural environments, chemical and

physical transformation in the materials, such as the biotransfer process of rock for soil

formation (pedogenesis), can be seen as a necessary and positive process. However, when

a rock is used as building material, the transformation induced by the microflora in

association with other environmental agents are clearly seen as a negative or destructive

process, both form cultural and economic viewpoint. Therefore, the concepts

“biodegradation” and “biodeterioration” leads to a systematization of these fields of

science (Hueck, 2001). The term biodeterioration was defined by Hueck in 1965 as “any

undesirable change in the properties of a material caused by the vital activities of living

organisms”. This term involves a negative connotation, whereas the term biodegradation

involves, while the term biodegradation involves a positive or useful connotation in

relation to ecology, waste management and environmental remediation.

Figure 2.4 shows the clear aptitude of different type of substrate to be colonized by

diverse microbial communities composed of bacteria, cyan bacteria, algae, fungi and

lichens, either epilithically or endolithically (Golubic et al., 1981).

Figure 2.4.Extensive lichen colonization. Palácio Nacional de Queluz, Portugal

State of the art 9


The degree of biological colonization of a stone surface depends not only on

environmental factors but also on the intrinsic properties of the material (Guillitte, 1995).

As the intrinsic properties of the material change over time as a result of the exposure to

weather, the bio-receptivity cannot be considered as a static property and more than one

type of bio-receptivity should be defined for each stone material according to the different

stages of deterioration. Guillitte defined three types of bio-receptivity:

- Primary or intrinsic bio-receptivity, which relates to the initial potential of

biological colonization of sound stones.

- Secondary bio-receptivity, which refers to the potential of biological

colonization of weathered stone.

- Tertiary bio-receptivity, which is the colonization potential of stone material

subjected to conservation treatments.

Moreover, in some situations a type of bio-receptivity not directly related to the

intrinsic properties of the material must also be considered. Exogenous deposits such as

soil, dust or organic particles can accumulate on the material and modify the initial

conditions of bio-receptivity. For such situation, Guillitte in 1995 suggested use of the

term “Extrinsic bio-receptivity”. Finally “Semi-extrinsic bio-receptivity” describes a type of

bio-receptivity that depends directly and simultaneously on the properties of the material

and on the deposits of exogenous substances. This situation occurs when the vegetation

colonizing the material is colonized by epiphytes or is parasitized by other organisms.

2.3.1 Material properties related to bio-receptivity

The bio-receptivity of building stones is described by their petrochemical

characteristics and petrophysical properties, such as pore space structure (e.g. porosity,

permeability, capillarity kinetics) and surface roughness, independently of the

colonization potential of the environment. The settlement, development and type of

biological colonization on building surfaces are chiefly dictated by bio-receptivity of the

material, environmental parameters (e.g. water regime, relative humidity, solar radiation,

temperature, wind, atmospheric pollution, etc.), amount and type of airborne microbial

contaminants, as well as specific microclimatic parameters (e.g. orientation, shading,

permanent capillarity humidity, etc.). Some researchers have suggested that such climatic

and environmental factors may have a greater influence on the pattern of colonization of

stone surfaces than the nature of the rock itself (Urzì et al., 2001). Nevertheless, the

diversity and abundance of biological colonization depend on the availability of water,

since all organisms need water for metabolic functions (Silva et al., 1997; Papida et al.,

2000; Bellinzoni et al., 2003; Gorbushina, 2007; Gladis and Shumann, 2011).

Thus, as the colonization of stone is largely associated with environmental

conditions, particularly water availability on the stone surface, properties related to the

absorption and movement of water through the stone pore structure will, in turn, be

related to bio-receptivity. However, the intrinsic stone properties are also important, this

properties related to bio-receptivity appraised by the different researchers in laboratory-

based primary bio-receptivity experiments are present in Table 2.1. The mineral

10 Chapter 2


composition, petrography, texture, chemical composition and open porosity of the stones

are the characteristics appraised by almost all authors.

Table 2.1. Stone characteristics appraised by several authors (Miller et al., 2012)

References

Gu

illi

tte

and

Dre

esen

(1

99

5)

Tia

no

et

al.

(19

95

)

Pap

ida

et a

l.

(20

00

)

Tom

asel

li e

t a

l.

(20

00

)

Pri

eto

an

d S

ilva

(20

05

)

Mil

ler

et a

l.

(20

06

)

Fav

ero

-Lo

ngo

et

al.

(20

09

)

Mil

ler

et a

l.

(20

09

an

d 2

01

0)

Texture / petrography • • • • • •

Open porosity (%) • • • • • • • •

Surface roughness (μm) • • • •

Bulk density (g·cm-2) •

Dry density (g·cm-3) •

Grain density (g·cm-3) •

Surface hardness •

Water content (%) • •

Capillarity coefficient (g·m-2·s-1/2) • • •

Degree of water saturation •

Permeability (kg·m-1·s-1·Pa) •

pH • • • •

Chemical composition • • • • • • •

2.3.2 Biomass quantification techniques

Regarding to the biomass quantification, different methods are available to

quantify and monitor microbial growth on the artificially colonized surfaces. Surface

cover area (%) by macroscopic observation and image analysis is the most common

method, followed by the Chlorophyll a extraction, In vivo chlorophyll a fluorescence and

Colorimetric measurements in the case of phototrophic organisms.

The use of different methods of quantifying biocolonization may induce significant

differences in the results and so it is difficult to compare them. In a near future it is

necessary to compare the efficiency of various methods of estimating biofilm biomass on

stone for each type of microorganisms and try to establish the most suitable method or

methods to monitor bio-receptivity. Some researchers have already compared the efficacy

of a variety of destructive and non-destructive methods to estimate phototrophic biomass

on stone (Prieto et al., 2004; De Muynck et al., 2009; Escadeillas et al., 2009; Miller et al.,

2010b).

State of the art 11


Image analysis, Colorimetric measurements and Chlorophyll a content have been

corroborated as good methods (Tiano et al.,1995; Pietro et al., 2004; Alum et al., 2009; De

Muynck et al., 2009; Escadeillas et al., 2009; Miller et al., 2010a, 2010b).

De Muynck et al. in 2009 evaluated algal biomass by means of colorimetric

measurements and image analysis for the quantification of area covered by algae based

upon a colour threshold in the CIELab colour space. Both techniques allowed a clear

distinction between fouled and unfouled areas.

On the other hand, Miller et al. in 2010a comparing surface cover areas by image

analysis and chlorophyll extraction method using dimethyl-sulphoxide (DMSO) as solvent,

obtained a good correlation between both techniques when considering lithotypes with

epilithic growth. However, when endolithic growth occurred, image analysis showed to be

insufficient to detect and thus to estimate total biomass on stone. In this case, the

researchers recommended a combination of both techniques since the chlorophyll a

extraction method appeared to estimate the total algal biomass present on and within the

stone sample.

Therefore, image analysis, colorimetric measurements and in vivo chlorophyll a

fluorescence appeared to be reliable methods to be used in vitro, in situ and on site since

they are non-destructive, easy, quick and yield reliable results of estimating epilithic

biomass on stone. In the case of the chlorophyll a fluorescence method it should be noted

that cells with chlorophyll content may be highly damaged even when their chlorophyll

signal emission are still observed, as chlorophyll molecules are highly resistant. In that

case healthy and altered structurally cells are quantified.

One practical application of laboratory-based bio-receptivity experiments would

be the establishment of a bio-receptivity index, i.e. to classify different rock types on a

scale according to their susceptibility to biological colonization. The definition of such

index has not yet been established for stone materials as this requires a complex study

analysing a large range of types of stone used in construction. However, some studies have

attempted to qualitatively categorize the bio-receptivity of different types of stones.

On the other hand, some studies have attempted to develop standardised

laboratory tests for assessing the bio-receptivity of stone materials, based on the several

procedures carried out by Guillitte and Dreesen in 1995. Shirakawa et al. in 2003

suggested an experimental set-up relying on characterization of stone samples, isolation of

microorganisms, growth of isolated or organisms, inoculation, incubation and

quantification of biomass. Guillitte and Dreesen in 1995 and Miller et al. in 2008 have

developed techniques for inoculating stones samples and incubating phototrophic biofilms

in growth chambers for bio-receptivity studies. Also Giannantonio et al., in 2008 and 2009

designed incubation chambers where nutrients amendments are distributed over material

samples using sprinkler mechanisms.

De Muynck et al. in 2009 evaluated twelve different strategies for the prevention of

algal fouling on two types of concrete, namely white concrete and autoclaved aerated

12 Chapter 2


concrete (AAC), with different degrees of primary bio-receptivity. These strategies were

aimed at decreasing the bio-receptivity and comprised the use of different surface

treatments: water repellents, which aim to decrease the bio-receptivity and combinations

thereof. The results showed that in untreated specimens the differences in the rate and

extent of fouling between specimens of AAC and white concrete were attributed to

differences in the intrinsic bio-receptivity of these materials, which are porous, may

contain organic adjuvants, and thus show a high primary bio-receptivity.

De Muynck et al. in 2009 also stated that the differences in the rate of drying and

the water availability at the surface of AAC and white concrete specimens could explain

the observed differences in the rate of colonization upon anchorage of the algae. The

findings of this research confirm those of Guillitte and Dreesen in 1995, who reported that

the bio-receptivity of AAC was higher than that of Portland cement mortar.

2.4. SUPERABSORBENT POLYMERS (SAPs)

Superabsorbent polymers (SAPs) are a new generation of materials in polymer

technology which is able to absorb a significant amount of liquid from the surrounding

and to retain the liquid within its structure without dissolving (Buchholz et al., 1998) see

figure 2.5 and 2.6.

Figure 2.5. Superabsorbent polymers are substances which can absorb many times their own weight of liquids by forming a gel (left: dry particle; right: swollen particle)

Figure 2.6. SAP based on polyacrylic acid: swelling mechanism (Mechtcherine et al., 2012)

State of the art 13


2.4.1 Classification

Superabsorbent polymers can be classified in many ways depending on different

aspects. Commonly, they are classified on the basis of presence or absence of electrical

charges located in the cross-linked chains, on the type of monomeric unit used in their

chemical structure or on the origin sources.

Depending on the basis of presence or absence of electrical charge located in the

cross-linked chains (Zohuriaan-Mehr, 2006) SAPs may be categorized to the following four

groups:

- Non-ionic;

- Ionic (including anionic and cationic);

- Amphoteric electrolyte (ampholytic) containing both acidic and basic groups;

- Zwitterionic (poly betaines) containing both anionic and cationic groups in

each structural repeating unit.

Based on the type of monomeric unit used in their chemical structure, the SAPs

can also be classified (Po, 1994; Zohuriaan-Mehr, 2006). The most used SAPs are cross-

linked polyacrylates and polyacrylamides.

According to original sources, SAPs are often divided in two main classes: synthetic

(petrochemical-based) and natural. The natural-based SAPs are usually prepared through

addition of some synthetic parts onto the natural substrates such as graft

copolymerisation of vinyl monomers on polysaccharides.

- Synthetic (petrochemical-based);

- Natural, that can also be divided into two main groups, hydrogels based on

polysaccharides and others based on polypeptides (proteins).

It should be noted that sometimes when the term “superabsorbent” is used

without specifying its type, it actually implies the most conventional type of SAPs, that is

the anionic acrylic that comprises a copolymeric net-work based on the partially

neutralized acrylic acid (AA) or acrylamide (AM).

2.4.2 History

Because of their ionic nature and interconnected structure, they absorb large

quantities of water and other aqueous solutions without dissolving. This makes them

ideally suited as absorbents of body fluids in many personal care products sold today,

including baby diapers adult incontinence products and feminine napkins.

The commercially important superabsorbent polymers are sodium salts of cross-

linked poly(acrylic acid), and graft copolymers of cross-linked poly(acrylic acid) and

starch. Cross-linked and swellable poly(acrylic acid) was described by W. Kern in 1938. He

made them by thermally polymerizing an aqueous solution of acrylic acid and

divinylbenzene. The synthesis, properties and physical chemistry of cross-linked

poly(acrylic acid) and a very similar material, cross-linked poly(methacrylic acid) were

14 Chapter 2


studied in depth by Kuhn, Katchalsky and co-workers in the early 1950s (Katchalsky et al.,

1952; Kuhn, et al., 1950). A first practical use of cross-linked potassium polyacrylate, made

by irradiating an aqueous solution of the monomer, was as a water immobilizing agent in

fire-fighting, as described by Bashaw and Harper in a 1966 patent (Bashaw et al., 1966).

And in 1968, Harper and co-workers claimed cross-linked polyacrylates to be useful as

absorbents in diapers (Harper et al., 1968).

In other patents, Harper and co-workers (Harper et al., 1972), and Harmon

(Harmon, 1972), claimed to use of similar materials in absorbent medical and personal

care products in the United States. Nevertheless, the large scale application of these

materials languished until the early 1980’s, when diapers containing superabsorbent

polymer were made and sold commercially in Japan (Nukushina, 1980). The products

were a great success in Japan and the idea was brought back to the United States by 1984.

The new superabsorbent diapers were then marketed in Europe by the late 1980’s. As a

result, in just over 10 years the super absorbent polymers industry grew to about 414,000

metric tons per year (Obenski, 1994).

2.4.3 Production

Monomers may be polymerized by the following methods: polymerization in

homogeneous systems and polymerization in heterogeneous systems.

The homogeneous polymerization techniques involve pure monomers or

homogeneous solutions of monomers and polymers in a solvent. These techniques can be

divided into two methods (see figure 2.7):

Bulk polymerization induces radical polymerization with for example a vinyl

group monomer. This polymerization is a type of polymerization by heating or UV

radiation (amongst others) without solvent usage or small amount of initiator. The feature

of bulk polymerization is that the polymerization rate is high and a relatively pure

polymer is obtained.

Solution polymerization is used to solve the problems associated with the bulk

polymerization because the solvent is employed to lower the viscosity of the reaction, thus

to help in the heat transfer and reduce auto acceleration. This system requires the correct

selection of the solvents. The initiator and monomer should be soluble in each other and

the solvent has to be suitable for boiling points regarding the solvent-removal steps. This

method has potential disadvantages such as the difficulty of remove the solvent from final

form causing degradation of bulk properties.

On the other hand, the heterogeneous polymerization occurs in a heterogeneous

solution of monomer and polymer in a solvent. These systems can be either suspension or

emulsion polymerization (see figure 2.8).

Suspension polymerization (also known as pearl, bead and granular

polymerization) is a process that uses mechanical agitation to mix the monomer or

State of the art 15


mixture of monomer in a liquid phase such as water, polymerizing the monomer droplet

while they are dispersed by continuous agitation. This process is used in the production of

sodium polyacrylate which is a SAP used in disposable diapers. A reactor filled with a

mechanical agitator is charged with a water insoluble monomer, initiator and chain-

transfer agent to control molecular weight. Droplets of monomer (containing the initiator

and chain-transfer agent) are formed. Near to the end of the polymerization the particles

are hardened, then are recovered by filtration and followed by washing step.

Emulsion polymerization is a type of radical polymerization that usually starts

with an emulsion or surfactant which are dissolved in water and water insoluble or poorly

water-soluble monomer is added in it. In this method, the polymerization is performed by

using soluble initiator (for example: benzoyl peroxide). In the water solution of surfactant

above a specified level, surfactant molecules associate to form a micelle. Surfactant is

comprised of hydrophilic and hydrophobic, and associate with hydrophilic for exterior

(water side). If a monomer is added into aqueous solution in which the surfactant forms

micelle, since a monomer is water-insoluble, it is taken in part into micelle and exist in it

as droplet. Polymerization initiator used with emulsion polymerization is water-soluble

and starts polymerization as radicals in water phase reach monomers in a micelle.

Figure 2.7.Schematic diagram of: a) bulk polymerization and b) solution polymerization

Figure 2.8.Schematic diagram of: a) suspension polymerization and b) emulsion polymerization

a) b)

a) b)

16 Chapter 2


2.4.4 Characterization

The following section contains the SAP testing methods that are very useful in a

practical point of view for academic and industrial analysts. Test methods for the

characterization of SAP are standardised by EDANA, an association of the nonwoven

industry (http://www.edana.org).

Swelling capacity as an important parameter to define the superabsorbents

depends on the osmotic pressure which is proportional to the concentration of ions in the

aqueous solution. As the ions in SAPs are forced closely together by the polymer network

there is a very high osmotic pressure inside and by absorption of water the osmotic

pressure is reduced by diluting the charges (see figure 2.6). Different tests to obtain the

absorption capacity, absorption against external pressure, speed of swelling and the ionic

sensitivity are presented.

FREE-ABSORBENCY CAPACITY

Generally, when the terms swelling or absorbency are used without specifying its

conditions, it implies uptake of distilled water while the sample is freely swollen that

means no load is put on the testing sample. There are several simple methods for the free-

absorbency testing which are dependent mainly on the amount of the available samples,

the samples absorbency level and the method’s precision and accuracy. In this section an

accurately description of the different available methods is presented.

- Tea-bag Method

This method is the most conventional, fast and able for limited amount of samples

(W0 = 0.1 – 0.3 g) (Kabiri et al., 2005). The SAP sample is placed into a tea-bag

(acrylic/polyester gauze with fine meshes) and the bag is dipped in an excess amount of

water or saline solution for one hour to reach the equilibrium swelling. Then excess

solution is removed by hanging the bag until no liquid is dropped off. The tea bag is

weighed (W1) and the swelling capacity is calculated by the following equation [2.1]. The

method’s precision has been determined to be around ±3.5%.

- Centrifuge Method

The centrifugal data are more accurate that the tea-bag method and are

occasionally reported in patents and date sheets (Andrade, 1976; Buchholz et al., 1994;

Buchholz et al., 1998). Thus, 0.2 g (W1) of SAP is placed into a bag (60x60 mm) made of

nonwoven fabric. The bag is dipper in 100 mL of saline solution for half an hour at room

temperature. It is taken out, and then excess solution is removed with a centrifugal

separator (3min at 250 g). Then, weight of bag (W2) is measured. The same stages are

carried out with an empty bag, and the weight of bag (W0) is measured. The swelling

capacity is calculated by the equation [2.2]:

[ 2. 1 ]

http://www.edana.org/

State of the art 17


Since the inter-particle liquid is noticeably removed by this method, comparing the

results obtained with the tea-bag method, the centrifuge method often gives more

accurate and lower values.

- Sieve Method

SAP sample (W1, g) is poured into excess amount of water or a solution and

disperse with mil magnetic stirring to reach equilibrium swelling (0.5-3 h depending on

the sample particle size). The swollen sample is filtered at desire time through weighed

100-mesh (150 μm) wire gauze (sieve). Then it is dewatered carefully and rapidly using a

piece of soft open-cell polyurethane foam (by repeated rubbing under the gauze bottom

and squeezing the foam) until the gel no longer slips form the sieve when it is held vertical.

(Kabiri et al., 2003; Kabiri et al., 2004). The quantitative figures of swelling can be

calculated by equation [2.3]:

Where, St is the swelling at time t, [g/g] (gram of absorbed fluid per gram of

polymer sample). At is the weight of water-absorbed polymer at time t, [g]. And B is the

weight of the sieve, [g]. This method, also called filtering and rubbing method, needs a

large amount of sample (1–2 g).

- Filtration Method

The swelling capacity can also be calculated from the volume increase between the

vacuum-dried state and the saturated state (Snoeck et al., 2014). A volume of fluid (W0)

was added to vacuum-dried SAP particles (W1), and the whole was filtrated after 1 day.

The amount of filtered fluid was recorded (W2). To ensure there was no influence of the

filter paper, the latter was saturated with the fluid prior to filtration. The volume increase

of the SAP was measured as the difference between the added water and the filtered

water. This volume increase is a measurement for the total absorption.

ABSORBENCY UNDER LOAD (AUL)

A second widely used test is the absorption against external pressure. The

absorbency under load (AUL) data is usually given in the technical data sheets by

industrial SAP manufacturers. When the term AUL is used without specifying its swelling

media; it implies an uptake of 0.9% NaCl solution while the testing sample is pressurized

[ 2. 2 ]

[ 2. 3 ]

[ 2. 4 ]

18 Chapter 2


by some loads. A typical AUL test is a simple but finely made device including a macro-

porous sintered glass filter plate (porosity # 0, d=80 mm, h=7 mm) placed in a Petri dish

(d=118 mm, h=12 mm). This weighed dried SAP sample (0.90±0.01g) is uniformly placed

on the surface of polyester gauze located on the sintered glass. A cylindrical solid load

(Teflon, d=60 mm, variable height) is put on the dry SAP particles while it can be freely

slipped in a glass cylinder (d=60 mm, h=50 mm). Desired load is placed on the SAP sample

(figure 2.9).

Saline solution (0.9% NaCl) is then added when the liquid level is equal the height

of the sintered glass filter. The whole set is covered to prevent surface evaporation and

probable change in the saline concentration. After 60 min, the swollen particles are

weighed again, and AUL is calculated using the following equation [2.5] (Ramazani-

Harandi et al., 2006):

Where, W1 and W2 denote the weight of dry and swollen SAP, respectively. This test

is taken as a measure of the swollen gel strength of SAP materials.

Figure 2.9. a) Typical AUL tester picture; b) description of the various parts (Zohuriaan-Mehr et al., 2008)

SWELLING RATE

- Vortex method

The vortex method is the most rapid and simple way to evaluate the SAP swelling

rate. Water or saline solution (50.0 g) is poured in a 100 mL beaker and its temperature is

adjusted at 30°C. It is stirred at 600 rpm using a magnetic stirrer (stirrer bar length 400

mm). Superabsorbent sample (mesh 50-60, W0=0.5-2.0 g) is added and a stopwatch is

started. The time elapsing from the addition of SAP into the fluid to the disappearance of

vortex (tvd) is measured. This swelling rate (SR) is calculated by the equation [2.6]:

[ 2. 5 ]

[ 2. 6 ]

a) b)

State of the art 19


Other version of the vortex method was described by Zohuriaan-Mehr and Kabiri

(2008). For this test, 100 g of demineralised water was added to a beaker. Then, a vortex

was made using a magnetic stirrer (400 rpm). Form the already obtained absorption

capacity, the specific amount of SAPs to absorb 100 g of demineralised water was added to

the beaker. The time was recorded until the vortex disappeared (n=10).

IONIC SENSITIVITY

To achieve a comparative measure of sensitivity of the SAP materials towards the

kind of aqueous fluid, a dimensionless swelling factor, f, is defined as follows (equation

[2.7]) (Zohuriaan-Mehr et al., 2003):

For large values of f mean that higher absorbency-loss of the sample swollen in salt

solutions. Therefore, SAPs with lower values of f are usually preferred. Negative values of f

reveal that the absorbency is not decreased, but it is increased in salt solutions.

2.5. CEMENT-BASED SYSTEMS CONTAINING SUPERABSORBENT POLYMERS

Superabsorbent polymers have recently found application in concrete technology.

In most applications, SAPs have been added in the dry state to the concrete mixture.

Figure 2.10 shows the evolution in time of the SAP in cementitious material, when dry SAP

particles come into contact with water during mixing of concrete, they rapidly absorb it

and form water-filled cavities (see figure 2.10.a). The kinetics of absorption and the

amount of fluid absorbed by the SAP depend both on the nature of the SAP and the cement

paste or concrete, in particular on the pore solution composition. Once the SAPs have

reached their final size, they form stable, water-filled inclusion (see figure 2.10.b), from

which the water is subsequently sucked into small capillary pores and consumed by

hydration of cement. The SAPs end up as empty pores in the cement paste (see figure

2.8.c). In the following sections a summary of the process of absorption and desorption of

the SAP in concrete is discussed.

2.5.1 Absorption

The SAP absorption is the result of a competitive balance between expansive and

shrinkage forces. High concentration of ions inside the SAP is needed in order to lead the

water flow into the SAP due to osmosis. Another factor that contributes to increase the

swelling is water salvation of hydrophilic groups present along the polymer chain.

However, the elastic forces counteract swelling of the SAP (Jensen et al., 2001).

The ionic strength of the aqueous solution is of special importance for the swelling

of the SAP. The ions when are in the solution they change the intermolecular and

intermolecular interactions of the polyelectrolytes due to shielding of charges on the

polymer chain. Especially the Ca2+ ions present in the pore solution of concrete can cause

[ 2. 7 ]

20 Chapter 2


additional interlinking of the polymer chains and limit their swelling (Mönnig, 2009).

Moreover, as the concentration of ions outside the SAP increases, the osmotic pressure

inside the gel decreases, leading to a reduced swelling of the SAP (Jensen et al., 2001).

Figure 2.10. Schematic evolution in time of the SAP in a cementitious material. a) Initial condition, with homogeneous dispersion of cement particles, water, SAP and aggregates; b) The SAP has reached final absorption; c) The water has been transported into the cementitious matrix and an almost empty

pore remains. (Mechtcherine et al., 2012)

Furthermore, the influence of particle size of the SAP should be taken into account.

For internal curing and increasing the freeze-thaw resistance, according to Jensen and

Hansen, large SAP particles (few hundred μm) may have a reduced efficiency due to

insufficient time for water uptake during mixing, whereas very small SAP particles (only 1-

4 μm) may also show reduced absorption because of the less active surface zone compared

to the bulk. To describe the kinetics of absorption within a group of SAP depending on its

particle size distribution the Fick’s second law of diffusion is used.

According to Snoeck et al. 2012 with the presence of cracks the SAPs are exposed

to the humid environment and swell, this swelling reaction seals the crack from intruding

potentially harmful substances. The concrete has a passive healing capacity of its own, if

the water is flowing into the crack the grains of cement that were unhydrated with the

water are hydrated producing new calcium silicate hydrate (C-S-H) which result in sealing

of small cracks. However, if instead of C-S-H is produced calcium carbonate (CaCO3) the

mechanism of autogenous is crack healing, which also blocks the crack. In both cases, the

SAP which can absorb water releases its taken-up fluid to the cementitious matrix for

further hydration facilitating the sealing and healing.

The absorption in cement pastes taking to account the differential swelling of

different sized particles of SAP is a complete process on the condition that the swelling

time is acceptable; in this case, the SAP absorbs mixing water (Snoeck et al. 2014).

2.5.2 Desorption

Desorption is produced when the cement paste self-desiccates due to hydration, a

gradient in water activity is generated within the concrete between the water in the SAP

and the pore fluid (Lura et al., 2007). Due to the hydration or external drying a gradient of

Aggregate

Water

Cement

SAP

c) b) a)

State of the art 21


water activity between the empting pores is generated. Additionally, the osmotic pressure

it is also contributing. The process of desorption of the SAP may be described as a

competition for water between the SAP and the cement paste (Mönnig, 2009).

According to Mönnig (2009), the water close to the surface of the polymers is lost

rapidly whereas the water closer to the core of the polymer must overcome more side-

chains in the polymer, which interact with the water molecules through van-der-Waals

forces.

Regarding to desorption of the SAP in cement past, this depends on the properties

of the SAP, on the kinetics of hydration, on the microstructure of the cement past and on

the interface between the SAP and the cement paste. According to Snoeck et al., when the

SAP particles desorb, they will form macropores. This means that by studying the macro-

porosity it is possible to determine the initial absorption of mixing water of the SAPs.

2.5.3 Workability of concrete and mortar containing SAP

As explained in previous sections, large amounts of water could be absorbed by the

SAP, this is because the cross-linked chains have dissociated ionic functional groups which

facilitate the absorption. As a consequence, the rheological properties of fresh concrete

containing SAP change dramatically. The change in the rheological properties have a direct

effect in other important parameters that are used to classify the workability of the fresh

concrete such as its fluidity, compactability and ability to be pumped. Thus, study and

understand the rheological behaviour of fresh concrete is important.

According to Bingham, the rheological behaviour of fresh concrete is most often

described using the equation [2.8]:

Where:

shear stress applied to the material;

yield stress;

plastic viscosity;

shear strain rate.

Jensen and Hansen mention that the addition of 0.4% of a certain type of SAP

relative to cement mass will lead to a lowering of the free w/c of 0.06, depending on the

type of polymer and the swelling characteristics. This change in the w/c will cause an

increase in the yield stress and in the plastic viscosity of concrete. In addition to this pure

water binding effect, it is believed that a further increase in the yield stress and plastic

viscosity will be caused by the physical presence of swollen SAP particles (Jensen, 2008).

Unfortunately, only few results are available in the literature.

[ 2. 8 ]

22 Chapter 2


2.6. CONSTRUCTION APPLICATIONS OF SAP IN CONCRETE

The use of SAP in construction applications is relatively recent and although more

research is needed to improve the application as a regular material in construction,

improvement on concrete properties and potential applications of SAPs are known.

2.6.1 Improvement on concrete properties

Due to the use of SAP in concrete it is possible to reduce the shrinkage (Jensen and

Hansen, 2002). This is because there is a control of the cracking during the early-age and

as a consequence an increment of the long-term durability. The quality of the curing is

directly related to the long-term durability. Water should be provided to the surface

and/or in the interior and water evaporation should hereby be limited.

SAP particles are able to provide a pore system to the cement that give it a

resistance to freezing and thawing. To resist these phenomena an exhaustive control in the

volumetric air content and size of the air voids is needed (Lura et al., 2007; Mechtcherine

et al., 2011). This is reached by using SAPs of a specific size.

On the other hand, the addition of SAPs during the concrete mixing produce a

rheology modification this is due to the decrease in the free water-cement ratio that leads

to an increase in the yield stress and plastic viscosity (Mechtcherine et al., 2011).

With the purpose of long-term durability and lower maintenance, another

important application of SAPs is self-sealing. SAP particles are able to seal the crack which

allows a recovery of the water-tightness of the structure (Snoeck et al., 2012).

Moreover, SAPs have a significant potential with crack healing, in this case a

special type of SAP that can hardly absorb alkaline water in fresh and hardened concrete is

used to absorb neutral or acidic water infiltrating through cracks (Snoeck et al., 2012;

Snoeck et al., 2014) is used for promoting autogenous healing of cementitious materials.

2.6.2 Potential applications

An overview of the main applications where SAP could be effectively used to

improve the construction process, performance and durability are presented in this

section.

In concrete structures, appropriate curing is essential to ensure they meet their

intended performance and desired durability. For this reason, one of the main applications

of the SAPs is in the internal curing (IC) where the SAP works as a reservoir to supply the

extra curing water needed to compensate for the shrinkage occurring in the cement paste

during hydration.

State of the art 23


Nevertheless, SAPs have many other additional applications in civil engineering.

Used as a methods for rapid stabilization of weak soils have been sought to support

military forces worldwide. Cement and lime have been the most effective stabilizers for

road and airfield applications, although, many non-traditional stabilizers have also been

developed and used. The treatment of one clay with cement resulted in relatively high

unconfined compressive strengths (UCS), whereas treating the same clay with quicklime

and calcium carbide resulted in lower UCS. Secondary stabilizers, including sodium

silicate, SAPs, a superplasticizer and an accelerator, were unsuccessful in improvement of

the UCS of a soil treated with cement, quicklime, or calcium carbide (Rafalko et al., 2007).

A formulation of linear anionic polyacrylamide mixed with aluminium chlorohydrate and

SAP at a ratio of 6:1:1 has been applied to make helicopter landing pads that minimizes

dust clouds during the helicopter operations (Orts et al., 2007).

In addition, to cement admixture, SAPs have been used as sealing materials in civil

engineering sector. Production of a sealing mat has been disclosed by Vogt et al., which

swells under the influence of water and in which a material that is made of superabsorber

is disposed between two purposes in structural and civil engineering, particularly for

building tunnels (Vogt et al., 2004).

SAPs like polyacrylamide or modified cross-linked poly(meth)acrylate, have been

used to absorb free water in a cement slurry to form a gel, releasing the absorbed water to

the cement hydration reaction as the cement sets. The absorption of water caused the

slurry to develop a solid-like structure (Zusatz et al., 2004). A cross-linked SAP

composition having low viscosity and high absorption capacity has been used to enhance

the absorbency to increase the humectancy and/or absorbency of a fibre matrix, to

improve the water retention of soil, and to increase the open time of cements (Anderson et

al., 2008).

24 Chapter 2


Materials and Methods 25


CHAPTER 3

MATERIALS AND METHODS

3.1. INTRODUCTION

The aim of this chapter is to describe the materials and the methodology used to

obtain the characterization of the SAPs as well as the behaviour of these SAPs once with

the mortars and end up with a set of specimens to study the bio-receptivity.

The chapter follows the outline shown in figure 3.1, four types of SAPs were

presented followed by the main tests performed in order to characterize the SAPs. An

experimental program to study the behaviour of the mortar combined with

superabsorbent polymers is proposed. Finally, the selected specimens to study the bio-

receptivity were defined and manufactured with the collaboration of the company Escofet

1886 S. A.

The experimental program was mainly carried out in two different laboratories:

the Laboratory of Structure Technology Luis Agulló (UPC) and the Magnel Laboratory for

Concrete Research (UGent).

3.2. MATERIALS

Three types of SAPs from the company BASF (BASF Construction Chemicals GmbH,

Ludwigshafen, Germany) and a SAP from the University of Ghent were used. Two of those

provided by the company BASF are in the experimental phase without the sheet data,

therefore the tests performed during the study is the only data available for them.

26 Chapter 3


The main characteristics provided by the companies are presented in the following

order, recycled SAP untreated (SAP 1), recycled SAP treated (SAP 2), virgin (SAP 3) and

TerraCottem Universal (SAP 4).

Figure 3.1. Outline of the experimental program

3.2.1 Recycled SAP untreated

Definition:

The product comes from recycling diapers and other commercial absorbent

products. In this case, the product is only subjected to a recycling process without any

subsequent treaty, as it can be seen in the figure 3.2 the result is a thick and

heterogeneous product similar to cotton balls.

SAPs CHARACTERIZATION

Absorption kinetics

Systematic procedure

Filtration method

- demineralised water

- artificial seawater

- sulphate solution

- cement slurry

Kinetic behaviour

Vortex test

MORTAR with SAPs

CHARACTERIZATION

Absorption and desorption test

Void volume

Consistency test

Define a set of

specimens to study

Define a set of specimens with

good properties to study

Dynamic vapour sorption (DVS)

Mercury intrusion porosity (MIP)

Bio-receptivity

Algal fouling test



Figure 3.2. SAP 1 – Recycled SAP untreated (BASF)

3.2.2 Recycled SAP treated

Definition:

As the product defined above (recycled SAP untreated), the product comes from

recycling diapers and other commercial absorbent products. However, in this case, after

the recycling the product is subjected to a treatment, as show the figure 3.3 the result in

comparison with the figure 3.2 is a thinner and homogenous material.

Figure 3.3. SAP 2 – Recycled SAP treated (BASF)

3.2.3 Virgin

Definition:

The product is a Superabsorbent Polyacrylate with relevant uses as a polymer.

28 Chapter 3


Composition:

- Polyacrylic acid

- Sodium salt

- Cross-linked

Technical characteristics:

- Form ..................................................................................................................................... granules

- Colour ........................................................................................................................................ white

- Glass transition temperature ............................... approx. 140 (approx. 101.3 hPa)

- Solubility in water ..................................................... insoluble, only capable of swelling

- Bulk density..................................................................................................................... ~ 700 g/l

- pH (1 g/l H20).............................................................................................................................. ~ 6

- Minimum ignition energy ........................................................................................... > 999 mJ

- Hygroscopy ................................................................................................................ hygroscopic

- No hazardous ingredients (GHS) according to Regulation (EC) No 1272/2008

Figure 3.4. SAP 3 – Virgin (BASF)

3.2.4 TerraCottem Universal

Definition:

The product is a physical soil conditioner designed to increase the water and

nutrients holding capacity of soils and growing media, increase plants’ root development

growth and survival rate and reduce the need for watering by up to 50%. The product is a

dry, free flowing, powdery-to-granular mixture of cross-linked hydroabsorbent polymers,

growth precursors and volcanic rock enriched with soluble, slow release and synthetic

nitrogen fertilisers. The product has an absorption capacity of a minimum of 4500 g

H20/100g in distilled water using Method of Analysis CEN EN 13041 and a minimum of

90% of the water contained in the polymers is plant available.

Composition:

- Mixture of cross-linked hydroabsorbent polymers ..........................................39.50 %

- Fertilisers ............................................................................................................................ 10.50 %

N total .............................................................................................................................. 5.00 %

P soluble in mineral acid ......................................................................................... 0.44 %

K soluble in water ...................................................................................................... 4.15 %



Micronutrients: B, Cu, Fe, Mn, Mo, Zn

- Growth precursors ............................................................................................................ 0.25 %

- Volcanic rock ..................................................................................................................... 49.75 %

Technical characteristics:

- Bulk density..................................................................................................................... ~ 800 g/l

- Dry matter............................................................................................................................. ~ 96%

- pH (1 g/l H20).............................................................................................................................. ~ 7

- Absorption capacity in distilled water...................................... min. 4500 g H20/100g

(Method of Analysis CEN EN 13041)

- Absorption capacity in a solution of 2g/l Ca(NO3)2 ............ min. 1500 g H20/100g

(Method of Analysis CEN EN 13041)

- Dry granular mixture free of micro-organisms

- Certified non-toxic

- Lifespan.................................................................................................................................. 8 years

Figure 3.5. SAP 4 – TerraCottem Universal (UGent)

3.2.5 Microscopic analysis

To obtain more detailed information about the shape, composition and dimensions

of the different SAPs microscopic analysis was performed by means of Leica microscope.

The following figures with scale 2, 1 and 0.5 mm were done.

An interesting parameter is the average of the diameters of different SAPs, to

obtain it the measurements were taken from the microscopic figures and they are

presented in the table 3.1. As the recycled SAP untreated is composed of filaments no

diameter average could be found.

Table 3.1. Average of the diameter [mm]

Code Diameter average

[mm]

SAP_1 -

SAP_2 0.848

SAP_3 0.755

SAP_4 2.072

30 Chapter 3


Figure 3.6. SAP 1 – Microscopic analysis


32 Chapter 3


3.3. ABSORPTION KINETICS

In order to determine the absorption of the SAPs two methods were used; a

systematic procedure and the filtration method according to Snoeck et al. (2012).

3.3.1 Systematic procedure

The swelling capacity was calculated by adding demineralised water to an amount

of 1 g of each SAP. The water was added drop wise till the SAPs become completely

saturated. Figure 3.10 shows the dry amount of each SAP and the SAP with the added

water. This method is subjective and the results may vary a lot, but it may give a fast first

impression of the swelling capacity. To ensure that the correct value was found, the

filtration test was used.

1 2 3 4

Figure 3.10. a) 1g of dry SAP; b) 1g of SAP after hydration

Table 3.2. Amount of water added to 1g of SAP

Code Dry SAP [g] Water [g]

SAP_1 1 55

SAP_2 1 60

SAP_3 1 95

SAP_4 1 15

1 2 3 4 2 3 1 2 3 4

a)

b)



3.3.2 Filtration method

The swelling capacity was calculated from the volume increase between the

vacuum-dried state and the saturated state. A fluid was added to vacuum-dried SAP

particles, and the whole was filtered after 24 hours as figure 3.11 shows. The amount of

filtered fluid was recorded. To ensure there was no influence of the filter paper, the latter

was saturated with the fluid prior to filtration. Also, during filtering, the whole was

covered by a lid, to minimize evaporation. The volume increase of the SAP was measured

as the difference between the added water and the filtered water. This volume increase is

a measurement for the total absorption.

Figure 3.11. SAP filtration after 24 hours

Several different fluids can enter a crack of a structure during its lifetime (Snoeck

et al., 2012). For this reason, the measurements were performed in demineralised water,

artificial seawater (with 48 g NaCl, 10 g MgCl2, 8 g Na2SO4, 1.4 g CaCl2 and 1.6 g MgBr2 for 2

L seawater), a sulphate solution (with 100 g Na2SO4 for 2L) and a filtered cement slurry

(obtained by mixing 200g CEM I 42.5 N in 2 L of water).

The absorption capacity was calculated using the following equation [3.1]:

3.4. KINETIC BEHAVIOUR AND SWELLING TIME DETERMINATION

To determine the swelling time the vortex test (Zohuriaan-Mehr and Kabiri, 2008)

was done (see figure 3.12). In order to test the SAPs, 100 g of demineralised water was

added to a beaker. Then, the vortex was made using a magnetic stirrer (400 rpm). From

the previous results of the absorption capacity the specific amount of SAPs to absorb 100 g

of demineralised water was added to the baker. The time was recorded until the vortex

disappeared and this time served as the swelling time.

[ 3. 1 ]

34 Chapter 3


Figure 3.12. Vortex test

3.5. INTERACTION WITH MORTAR

As it can be seen from the swelling capacity the results depend greatly on the fluid

used. For this reason, and with the purpose of determine the amount of extra water due to

the SAP needed to make the specimens with mortar, consistency tests with the mortar

mixture using EN 1015-3 were performed (figures in Annex A). The extra water due to

SAP was added slowly making a consistency test between each step until reach the

standardised mortar consistency. A summary of the results obtained is shown in Table

3.3.

Table 3.3. Added water until the expected consistency

Code Extra

water [g]

Consistency test

Flow table d1 [mm] Flow table d2 [mm] Average [mm]

REF-SAP_1 - 159 160 159.5

SAP_1

40.0 120 123 121.5

60.0 135 136 135.5

70.0 148 150 149.0

75.0 159 160 159.5

REF-SAP_2 - 159 161 160.0

SAP_2

40.0 119 118 118.5

50.0 125 127 126.0

60.0 131 131 131.0

70.0 145 148 146.5

75.0 161 160 160.5

REF-SAP_3 - 159 160 159.5

SAP_3 40.0 151 150 150.5

50.0 159 160 159.5

REF-SAP_4 - 160 159 159.5

SAP_4

5.0 120 121 120.5

30.0 126 128 127.0

60.0 135 134 134.5

75.0 145 147 146.0

80.0 155 154 154.5

85.0 154 155 154.5

95.0 157 158 157.5

105.0 159 160 159.5

Vortex



The reference mortar mixture with a water-to-cement ratio of 0.50 was composed

of Portland cement (CEM I 52.5 R) (450 g), silica sand (1350 g) and water (225 g). Other

mixtures with different amount of SAP expressed as mass% (m%) of cement weight and

additional water were used. All compositions were mixed according to the standard UNE-

EN 196-1. The mixing procedure was as follows:

- 0 s: cement and water were added;

- 0-30 s: immediately after contact of water (only the water to satisfy the water-

to-cement ratio) with cement, mixing is started at 140 rpm;

- 30-60 s: sand is steadily added;

- 60-90 s: the mixing speed is increased to 285 rpm;

- 90-180 s: during the first 30 s of a subsequent 90 s stop, the mortar is scraped

from the walls and bottom part of the bowl;

- 180-240 s: mixing at 285 rpm;

- 240-300 s: during the last 30 s of the stop SAPs (depending on the mixture

composition) were dry added;

- 300-330 s: mixing at 140 rpm;

- 330-360 s: during this 30 s half of the amount of SAPs water (depending on the

mixture composition) were added;

- 360-420 s: mixing at 140 rpm;

- 420-450 s: the other half of the amount of SAPs water were added;

- 450-510 s: final mixing at 140 rpm.

Table 3.4 lists all mortar pastes investigated with the mixture composition of

different amounts of SAP.

Table 3.4. Composition of the mortar mixtures

Code Cement [g] Sand [g] Water [g] SAP [g] Additional

water [g]

REF

225 1350 450

- -

SAP_1 (0.5 m%)

2.25

37.5

SAP_2 (0.5 m%) 37.5

SAP_3 (0.5 m%) 25.0

SAP_4 (0.5 m%) 52.5

SAP_1 (1 m%)

4.50

75.0

SAP_2 (1 m%) 75.0

SAP_3 (1 m%) 50.0

SAP_4 (1 m%) 105.0

SAP_1 (4 m%)

18.00

300.0

SAP_2 (4 m%) 300.0

SAP_3 (4 m%) 200.0

SAP_4 (4 m%) 420.0

SAP_1 (10 m%)

45.00

750.0

SAP_2 (10 m%) 750.0

SAP_3 (10 m%) 500.0

SAP_4 (10 m%) 1050.0

36 Chapter 3


Using the mixtures of the table 3.4, three specimens of 40x40x160 mm3 each (n=3)

were made. After the manufacturing the specimens were conditioned in a climatic

chamber at 29 and 56% relative humidity during the setting time (24 hours) and

covered with a plastic. Then, were demoulded and introduced into the humidity chamber

during the curing time (28 days).

The specimens manufactured and cured 28 days in wet condition were tested in

order to compare the absorption and desorption between the reference mortar specimens

and the specimens with SAPs. In order to know the void volume, the submerged weight

was determined. The purpose of these tests is to determine which specimens will have

better properties to be tested with accelerated algal fouling test.

During the manufacture some problems with the specimens of 10 m% of the SAPs

were found. The additional amount of water due to the SAP was not the expected, and

some water remained without absorbing as show the figure 3.13. This excess water is

unwanted, and those mixtures were not studied.

Figure 3.13. Excess water in the mortars with 10% of SAP

3.5.1 Absorption and desorption test

To study the absorption and desorption each set of specimens (n=3) were

weighted at different steps:

- At time 0 hours, after the 28 days curing;

- At time 72hours, after dried in an oven (T = 50 );

- At time 144 hours, after 72 h additional hours of drying (T = 50 ), in this step

two measurements were done, to ensure that the specimens were in a stage

with a constant weight that could be considered stable. Then the specimens

were immersed in a container filled with water (see figure 3.14);

- At time 168, after 24 h of immersion the weight measurements were done

using the dry weight (removing the specimens from the water and drying the

surface);

- At time 192, the same procedure explained was done to obtain the dry weight.

Excess water



Figure 3.14. Specimens during the immersion process

3.5.2 Void volume

To determine the volume of voids the American standard ASTM C642-06 was

followed with some changes in the performance in order to ensure that the SAPs were not

damaged due to the high temperatures of the oven.

The test was performed for each set of specimens (n = 3) at different steps:

- At time 0 hours, after the 28 days curing;

- At time 72hours, after dried in an oven (T = 50 );

- At time 144 hours, after 72 h additional hours of drying (T = 50 ), in this step

two measurements were done, to ensure that the specimens were in a stage

with a constant weight that could be considered stable. Then the specimens

were immersed in a container filled with water;

- At time 168, after 24 h of immersion the weight measurements were done

using an especial weighing scales (see figure 3.15) to obtain the submerged

weight;

- At time 192, the same procedure explained at the previous step was done.

Figure 3.15. Weighing scale to obtain the submerged weight

38 Chapter 3


The Archimedes’ principle was applied to obtain the void volume. Using this

principle and applying the following formulas to the dry and submerged weight of each set

of specimens.

Using the equations [3.2] and [3.3] the volume of the specimen mass is

obtained.

The volume of the specimen mass has to be subtracted from the geometrical

volume of the specimen :

3.6. SPECIMENS FOR ACCELERATED ALGAL TEST

A set of samples to study the bio-receptivity were manufactured, after determining

the best overall mixtures. The specimens for the accelerated algae fouling test have a

different shape, a polyurethane moulds of six specimens were used (see figure 3.16), and

each specimen has 80x80x20 mm3.

Since the volume required to produce the specimens is high the instrumentation

used to manufacture were different, the methodology explained in section 3.5 according

with the standard UNE-EN 196-1 have to be modified. The mixing procedure was a

consecutive addition of the elements with an interval of one minute between each material

added as follows:

- 0 s: arid;

- 60 s: cement;

- 120 s: water;

- 180 s: SAP;

- 240 s: additional SAP water.

[ 3. 2 ]

[ 3. 3 ]

where:

E is the buoyant force of a given body;

is the volume of the displaced fluid [ ];

is the fluid density (water );

is the acceleration due to gravity ( );

is the dry weight of the specimen [ ];

is the submerged weight of the specimen.

[ 3. 4 ]

[ 3. 5 ]



Figure 3.16. Polyurethane moulds (80x80x20 mm3)

In order to improve the porosity another dosage apart of the standardised were

taken into account to produce the specimens. Table 3.5 shows the dosage used to produce

the specimens.

Table 3.5. Dosage of the specimens to study the bio-receptivity

Code Cement

[kg]

Sand

[kg]

Water

[kg]

SAP

[kg]

Additional

water [kg]

REF_NORM (C1)

12.3 36.9

(standard) 8.2

- -

SAP_3_NORM (V1)

0.5 4.0

SAP_4_NORM (T1)

REF_POROSITY (C2)

8.9 35.9

(0-5mm) 6.0

- -

SAP_3_ POROSITY (V2)

0.4 3.0

SAP_4_ POROSITY (T2)

To achieve the growing of the algae, a pH around 9 is needed. For this reason, the

specimens’ surface should be carbonated. In this stage, more specimens apart of the algal

fouling test (80x80x20 mm3) were manufactured to study the structure of the specimens

with the effect of the carbonation (see later on in paragraphs 3.7 and 3.8). The specimens

for the algal fouling test were carbonated during 30 days in a carbonation chamber of CO2

with a concentration of 10% CO2.

Cement pastes have a typical pH around of 13 which does not allow the growth of

organisms, for this reason, the specimens need to be carbonated. The carbonation is the

result of the dissolution of CO2 in the concrete pore fluid and this reacts with calcium from

calcium hydroxide and calcium silicate hydrate to form calcite (CaCO3). The affected depth

from the concrete it is easy shown by the use of phenolphthalein indicator solution, when

40 Chapter 3


the solution comes into contact with the sample becomes pink with concretes with pH

values in excess of 9 and colourless at lowest levels of pH.

The test was carried out by spraying the indicator on freshly exposed surface of

concrete broken from the specimens and the result is colourless (see figure 3.17), this

means that the specimens were able to perform the accelerated algae fouling test.

Figure 3.17. Samples after the phenolphthalein test fully carbonated

3.7. DYNAMIC VAPOUR SORPTION (DVS)

The dynamic vapour sorption apparatus used was from Surface Measurement

System, London, UK (see figure 3.18.b). The general principle of a sorption measurement

is shown in figure 3.18.a. The most important part is the humidity-controlled sample

chamber and the microbalance module. By measuring the mass change as a function of

time with changing relative humidity (RH) of the sample versus an empty reference,

sorption isotherms can be calculated (Snoeck, 2014). The humidity is regulated by mixing

humid and dry nitrogen gas. Figure 3.18.b shows the storage of samples in the presence of

soda lime and the material studied next to the DVS equipment.

The temperature was set at 20 and the mass criterion to proceed to the next RH

step was dm/dt < 0.002 wt·%/min. Dried cement pastes were first conditioned at 0% RH

inside the DVS equipment followed by an adsorption-desorption cycle (Snoeck et al.,

2014). The RH level at which samples (5 – 10 mg) were subsequently equilibrated

included 0-1-2-5-10-20-30-40-50-60-70-80-90-95-98% RH.

The larger the particle size, the longer the time required for equilibration of the

masses while increasing or decreasing the RH. If the sample is too big, the time to reach

equilibrium is much higher and impracticable (Snoeck et al., 2014). Sample size of 500-

1000 μm was used (see figure 3.19.a) and the test the samples were pre-dried one week

with vacuum-drying (20±2 ) at 0.1 bar (see figure 3.10.b).

C1 C2

V2

T2 T1 V1



Figure 3.18. a) Schematic overview of the dynamic vapour sorption (DVS) methodology; b) the used equipment, where samples stored in the presence of soda lime are put into the sample container and

the whole is put in the DVS equipment.(Snoeck et al., 2014)

Figure 3.19. a) Particles of 500 μm; b) Drying of the sample

3.8. MERCURY INTRUSION POROSIMETRY (MIP)

To prepare the specimens for the MIP test they were cut and dried using the

freeze-drying method. The specimens were dried in liquid nitrogen and placed in a freeze-

dryer instantaneously for 3 weeks by means of Mini Lyotrap freeze dryers from LTE

Scientific. The freeze-drying method is used frequently for MIP measurements (Collier et

al., 2008) since it preserves the pores in the fine pore region (r < 5 mm) (Konecny et al.,

1993; Korpa et al., 2006) and also stop hydration.

Mercury intrusion porosimetry (MIP) has become one of the most widely used

methods for investigating the pore structure in cement based materials since the work of

Winslow and Diamond in the 1970s. The test consists in weighing and placing the dried

samples into the chamber. Then, the air in the chamber is evacuated and mercury fills up

the chamber. As the applied pressure is increased, mercury is forced to intrude into the

samples gradually. The mercury intrusion volumes and the corresponding applied

pressure are recorded at every pressure step. The mercury intrusion volume and the

corresponding applied pressure provide the basic data to analyse the pore structure. With

the assumption that pores are cylindrical, entirely and equally accessible to mercury, the

a) b)

a) b)

42 Chapter 3


applied pressure can be converted into the pore diameter by using the equation [3.6]

suggested by Washburn in 1921:

where, D is the equivalent pore diameter, P is the applied pressure, is the surface

tension of mercury and is the contact angle between mercury and solid surface.

Figure 3.20. Equipment used for carried out the MIP test (left: lower pressure; right: higher pressure)

MIP measurements can only provide a valid estimation of pore structure, when the

sample has the property that each pore is directly accessible to mercury or can be reached

by mercury through large pores (Diamond, 2000; Moro et al., 2002). However, research

revealed that the pore size of the cement-based materials is randomly distributed and

most pores are connected to the surface of the sample through a chain of pores with

varying sizes and shapes. With such a pore structure, mercury cannot intrude into large

pores until the applied pressure is sufficient to force mercury to go through smaller neck.

As a result, the volume of these large pores is continued as the volume of smaller necks.

This is referred to as the “accessibility effect” (Diamond, 2000). The large pores that are

accessible to mercury through smaller necks are called ink-bottle pores. The smaller necks

are called neck pores. The ink-bottle pores and the neck pores constitute the total

porosity. The minimum size of pores detected by MIP is about 7 nm. Mindess and Young in

1981 suggest that pores smaller than 10 nm do not contribute to water and ionic

transport.

3.9. AIR-VOID ANALYSIS

A rapid air-void test was performed to the bio-receptivity specimens in order to

determine the air pores and the pores caused by the SAPs (since the SAP is dry the pores

due to SAP are analysed like air voids). For this test, the plate specimens (8x8x2 cm3) were

used. And, the test was performed on both sides; the 8x8 cm2 face that was in contact with

the mould and also the face that was not covered by the mould during the curing.

[ 3. 6 ]



First the specimens were polished and put in an oven at 40 to let them dry.

Afterwards, the specimens were coloured black by gently dragging a broad tipped marker

pen over the surface in slightly overlapping lines. When dry (few seconds) the specimens

were turned 90° and coloured again. The colouring was done making sure that the surface

was covered and the voids not filled with black ink. Then, the specimens were dried in the

oven, and subsequently dry powder (BaSO4) was sprinkled over the surface. The BaSO4

powder has an average grain size of 2 μm, for this reason it fills into the air voids by

tamping a hard rubber stopped over the surface of the specimen. Finally, when all voids

appeared filled the excess powder was removed by dragging, with same pressure, a

smooth edged dense spatula one time over the surface, and the surface was then cleaned

smoothly with a tissue. The final result of the surface is seen on figure 3.21.

C1

C2

V1

V2

T1

T2

Figure 3.21. Final result of the surface (left: contact with mould and right: not contact with mould)

The air voids were analysed by means of Rapid Air 457 (see figure 3.22), the

system is an automated system for analysis of air content in hardened concrete and it is

capable of analysing the air void system either according to ASTM C 457 8 or EN 480; in

this study the measurements were done according EN 480. The analysis was performed

using 3 traverse lines per frame, and the traverse length was 2400 mm. The ratio paste

volume to the total volume, was calculated using the dosage and the density of the

materials. Those calculations are shown in table 3.6.

44 Chapter 3


Figure 3.22. Air void analyser, Rapid Air 457

Table 3.6. Calculated volume ratio of the paste to the total volume

Code Vpaste/Vtotal [%]

REF_NORM (C1) 45.7

SAP_3_NORM (V1) 52.1

SAP_4_NORM (T1) 52.1

REF_POROSITY (C2) 38.8

SAP_3_ POROSITY (V2) 45.3

SAP_4_ POROSITY (T2) 45.3

Results of SAPs and mortar characterization 45


CHAPTER 4

RESULTS OF SUPERABSORBENT AND MORTAR

CHARACTERIZATION

4.1. INTRODUCTION

The aim of this chapter is to define the set of specimens to study the bio-

receptivity. To reach this objective, a detailed study of the results obtained with the tests

described in the chapter 3 is needed. The results and the analysis are structured mainly in

three parts, the SAP’s characterisation, the mortar characterisation, and the suitable

specimens for study the bio-receptivity.

Defined the specimens for the bio-receptivity, the characterization of them is also

presented in this chapter. The studied main parameter of these specimens is the porosity,

and with the purpose of define the porosity in detail and at different levels, the results of

different test are analysed and compared at the end of this chapter.

4.2. SAPs CHARACTERIZATION

Table 4.1 and figure 4.1 show the average of the results (n=3) with the standard

deviation of the absorption of SAPs in demineralised water, seawater, Na2SO4 and cement

filtrate solution. The swelling time until full saturation of particles is achieved, is also

shown in that table.

46 Chapter 4


The ionic sensitivity of each SAP toward the different aqueous fluids used is

presented in table 4.2 with the dimensionless swelling factor f defined in the equation

[2.6].

Table 4.1. Absorption of SAPs [g fluid/g SAP] in different solutions and the swelling time [s]


Δm/m demineralised water 259.65 ± 11.85 322.99 ± 21.12 291.75 ± 12.44 240.30 ± 95.77

Δm/m seawater 20.59 ± 0.83 18.70 ± 1.64 20.15 ± 0.21 17.03 ± 5.23

Δm/m Na2SO4 32.98 ± 1.25 28.66 ± 2.17 31.88 ± 0.84 25.53 ± 4.22

Δm/m cement filtrate solution 24.06 ± 1.68 12.16 ± 0.99 11.83 ± 0.86 19.27 ± 5.39

Swelling time [s] 131.15 ± 13.75 223.16 ± 10.02 193.12 ± 9.53 793.54 ± 282.19

Comparison of the results is possible because the variables are independent

excluding the TerraCottem (SAP_4), due to the fact that is not a homogeneous SAP with a

significant part of the components that do not contribute to the absorption.

Figure 4.1. Absorption of SAPs with different fluids a) demineralised water, b) seawater, c) Sodium sulphate and d) cement filtrate solution

0.00

50.00

100.00

150.00

200.00

250.00

300.00

350.00

400.00


Δm

/m d

em

ine

rali

sed

wa

ter

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00


Δm

/m s

ea

wa

ter

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00


Δm

/m N

a2S

O4

0.00

5.00

10.00

15.00

20.00

25.00

30.00

35.00


Δm

/m c

em

en

t fi

ltra

te s

olu

tio

n

a) b)

c) d)



The results of the filtration test shows that the values of the absorption in

demineralised water of SAP 4 obtained is greater than the value provided by the

manufacturer which is 45 g of demineralised water for 1 g of SAP. For the other SAPs this

comparison is not possible due to the fact that the manufacturers do not provide this data.

From figure 4.1 it can be seen that the absorption in filtered cement slurry is lower

than in demineralised water, this is because the charge screening effect resulting from the

cations K+, Na+, Mg2+ and Ca2+ in the slurry. The ionic repulse of the negatively charged

groups is lower and produces the absorption decreases. Taking into account the decrease

of the absorption values the SAPs follow two sequences, SAP 1 and SAP 4 the following

order: demineralised water, Na2SO4, cement filtrate solution and seawater. Nevertheless,

SAP 2 and SAP 3 follow the order: demineralised water, Na2SO4, seawater and filtrate

solution.

Table 4.2. Dimensionless swelling factor, f [-]

Seawater Na2SO4 Cement filtrate solution

SAP_1 0.92 0.87 0.91

SAP_2 0.94 0.91 0.96

SAP_3 0.92 0.88 0.95

SAP_4 0.93 0.89 0.92

Figure 4.2. Dimensionless swelling factor, f [-]

As all values obtained with the studied SAPs are positive this means that no

increase of absorbance with salt solutions is expected. Contrary, due to the fact that in all

cases the values are close to the unit, all studied SAPs will have a loss of absorbance when

they were in saline solutions.

4.3. MORTAR CHARACTERIZATION

To characterize the mortar with SAPs different proportions of superabsorbent

were used. The amount of SAP used to manufacture the specimens is represented as a

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

0.80

0.90

1.00

SAP_1 SAP_2 SAP_3 SAP_4 Dim

en

sio

nle

ss s

we

llin

g f

act

or

f [

-]

Seawater Na2SO4 Cement filtrate solution

48 Chapter 4


percentage of the cement mass, using the following percentages of each SAP, 0.5 m%, 1

m%, 4 m% and 10 m%. All cases were studied by absorption and desorption test and also

submerged weight in order to determine the porosity.

4.3.1 Absorption and desorption test

Table 4.3 presents the results of the absorption and desorption test as well as the

submerged weight for all cases.

Table 4.3. Weight values at each step [g]

Code After

curing 13/10/15

Drying (50°C) Immersion

Dry weight Submerged weight

Accumulated time (h)

0 72 1441 1442 168 192 1442 168 192

Time (h) 0 72 1441 0 24 48 0 24 48

REF 566.067 549.300 541.600 542.067 563.700 563.933 286.433 306.600 306.867

SAP_1 (0.5 m%) 540.533 519.333 508.600 509.000 533.533 536.767 255.567 281.067 281.367

SAP_1 (1 m%) 547.133 520.733 507.067 510.133 542.833 542.933 259.333 288.133 288.433

SAP_1 (4 m%) 505.300 449.400 431.300 339.700 490.233 490.567 168.667 238.300 238.567

SAP_1 (10 m%) 490.100 377.467 351.067 384.300 427.200 426.367 181.500 169.567 169.633

SAP_2 (0.5 m%) 555.900 533.367 522.600 523.033 551.967 552.133 268.833 295.000 295.167

SAP_2 (1 m%) 562.433 534.533 524.167 524.567 555.067 555.433 272.733 299.867 300.167

SAP_2 (4 m%) 523.233 465.733 448.767 449.133 503.133 503.367 213.167 251.233 251.667

SAP_2 (10 m%) 481.467 376.167 339.433 431.767 417.433 415.567 197.000 176.167 176.600

SAP_3 (0.5 m%) 552.600 529.733 518.400 518.867 546.433 546.567 264.033 289.633 283.133

SAP_3 (1 m%) 552.033 524.700 513.800 514.000 544.167 544.333 249.033 286.033 286.400

SAP_3 (4 m%) 527.433 472.433 457.233 457.567 502.333 502.767 208.567 243.733 244.233

SAP_3 (10 m%) 472.033 399.533 356.267 464.533 455.500 455.867 229.833 204.267 204.933

SAP_4 (0.5 m%) 554.200 530.300 520.533 520.967 550.600 550.600 273.233 299.467 299.533

SAP_4 (1 m%) 546.267 522.867 512.433 512.900 543.033 529.425 254.125 287.000 287.200

SAP_4 (4 m%) 530.300 485.500 464.133 374.633 520.167 518.667 196.000 267.800 268.033

SAP_4 (10 m%) 479.267 402.067 383.867 351.467 460.133 458.233 163.000 207.200 207.367

1441 weight of the drying at time 144h

1442 weight using a different weighing scale to obtain the submerged weight

To determine the real amount of water that the specimens evaporate during the

drying process in the oven the difference between the initial weight (after curing) and the

weight at the time 72 h, then the difference between the initial weight and the time 1441 h.

Following the water absorbed is defined between the initial weight before the immersing

the specimens (time 1442 h) and the time 168 h and then the difference between the

weight before the immersing and the time 192 h. The values of this evaporated and

absorbed water are presented in the table 4.4.



Evaporated stages are presented in the figure 4.3 whereas the absorbed are in the

figure 4.4 in both figures all the SAPs with all the different percentages are presented.

The evaporated values are all negatives as it can be seen in the drying values of the

table, furthermore the values increase with the time this means that the loss of the water

also increase with the time. With the immersion, positive values pointing the absorption

are expected, however, some specimens with 10 m% do not have the expected behaviour.

Table 4.4. Amount of evaporated and absorbed water [g]

Code After

curing (13/10/15)

Drying (50°C) Immersion (Dry weight)

Time (h) 0 72 144 0 24 48

REF 0.000 -16.767 -24.467 0.000 21.633 21.867

SAP_1 (0.5 m%) 0.000 -21.200 -31.933 0.000 24.533 27.767

SAP_1 (1 m%) 0.000 -26.400 -40.067 0.000 32.700 32.800

SAP_1 (4 m%) 0.000 -55.900 -74.000 0.000 150.533 150.867

SAP_1 (10 m%) 0.000 -112.633 -139.033 0.000 42.900 42.067

SAP_2 (0.5 m%) 0.000 -22.533 -33.300 0.000 28.933 29.100

SAP_2 (1 m%) 0.000 -27.900 -38.267 0.000 30.500 30.867

SAP_2 (4 m%) 0.000 -57.500 -74.467 0.000 54.000 54.233

SAP_2 (10 m%) 0.000 -105.300 -142.033 0.000 -14.333 -16.200

SAP_3 (0.5 m%) 0.000 -22.867 -34.200 0.000 27.567 27.700

SAP_3 (1 m%) 0.000 -27.333 -38.233 0.000 30.167 30.333

SAP_3 (4 m%) 0.000 -55.000 -70.200 0.000 44.767 45.200

SAP_3 (10 m%) 0.000 -72.500 -115.767 0.000 -9.033 -8.667

SAP_4 (0.5 m%) 0.000 -23.900 -33.667 0.000 29.633 29.633

SAP_4 (1 m%) 0.000 -23.400 -33.833 0.000 30.133 30.267

SAP_4 (4 m%) 0.000 -44.800 -66.167 0.000 145.533 144.033

SAP_4 (10 m%) 0.000 -77.200 -95.400 0.000 108.667 106.767

These results are mainly influenced by the absorption and desorption of the most

external porosity, in that sense it is necessary to take into account that one face of the

prismatic specimens (which does not touch the mould) has more porosity. The fact is that

the external face has hydrated particles of SAP that remain there making a big porous

when the concrete get hard. These outer particles of SAP has a similar behaviour observed

in the filtrated test with demineralised water since they are not completely surrounded by

the mortar and have direct contact with the water when the specimens were immersed,

giving an increment of the absorption.

50 Chapter 4


Figure 4.3. Amount of evaporated water due to the drying in different SAPs:

a) SAP 1, b) SAP 2, c) SAP 3 and d) SAP 4

For the graphs of the figure 4.3 it can be seen that the loss of water increase with

time and with higher percentages of SAP. Using small percentages of SAP (0.5 m% and 1

m%) the behaviour during the drying is similar for all super absorbents. Whereas using

huge percentages (4 m% and 10 m%) the water loss during the first 72 h is greater using

SAP 1 and SAP 2, and following the same behaviour at time 144 h the same mortars reach

high values of evaporated water.

The general behaviour is faster water evaporation during the first period of drying

(72 h) and then the process is slower till 144 h. However, the mortar with SAP 3 and

percentage (10 m%) is not following this behaviour and continues the growing with

approximately the same slope. This might point that with 72h the sample still has not

reached the point of dryness that the other samples have achieved and the loss is smaller.

-160

-120

-80

-40

0 0 72 144

Δw

eig

ht

(g)

Time (h)

REF SAP_1 (0.5 m%)

SAP_1 (1 m%) SAP_1 (4 m%)

SAP_1 (10 m%)

-160

-120

-80

-40

0 0 72 144

Δw

eig

ht

(g)

Time (h)

REF SAP_2 (0.5 m%)

SAP_2 (1 m%) SAP_2 (4 m%)

SAP_2 (10 m%)

-160

-120

-80

-40

0 0 72 144

Δw

eig

ht

(g)

Time (h)

REF SAP_3 (0.5 m%)

SAP_3 (1 m%) SAP_3 (4 m%)

SAP_3 (10 m%)

-160

-120

-80

-40

0 0 72 144

Δw

eig

ht

(g)

Time (h)

REF SAP_4 (0.5 m%)

SAP_4 (1 m%) SAP_4 (4 m%)

SAP_4 (10 m%)

a) b)

c) d)



Figure 4.4. Amount of absorbed water due to the immersion in different SAPs: a) SAP 1, b) SAP 2, c) SAP 3 and d) SAP 4

In figure 4.4 the amount of absorbed water is presented. The general trend is an

increment of weight with the time as expected due to the absorption. However, in the

cases using 10 m% of SAP 2 and SAP 3, it can be observed from the figure 4.4.b and 4.4.c a

decrease in weight, this behaviour indicates that mortars are not able to absorb water.

Comparing all SAPs, using small percentages of SAP (0.5 m% and 1 m%) the

absorption values are similar in all cases and the values are near to the control behaviour

which has no contribution of any super absorbent. This effect is unwanted as absorption is

needed for the algae fouling to be higher.

Since the high values of absorption are reached with 4 m% of super absorbent

polymer in all cases, a detailed study to the values obtained with this percentage is

presented in the figure 4.5 to compare the results with all the super absorbents.

-45

0

45

90

135

180

0 24 48

Δw

eig

ht

(g)

Time (h)

REF SAP_1 (0.5 m%)

SAP_1 (1 m%) SAP_1 (4 m%)

SAP_1 (10 m%)

-45

0

45

90

135

180

0 24 48

Δw

eig

ht

(g)

Time (h)

REF SAP_2 (0.5 m%)

SAP_2 (1 m%) SAP_2 (4 m%)

SAP_2 (10 m%)

-45

0

45

90

135

180

0 24 48

Δw

eig

ht

(g)

Time (h)

REF SAP_3 (0.5 m%)

SAP_3 (1 m%) SAP_3 (4 m%)

SAP_3 (10 m%)

-45

0

45

90

135

180

0 24 48

Δw

eig

ht

(g)

Time (h)

REF SAP_4 (0.5 m%)

SAP_4 (1 m%) SAP_4 (4 m%)

SAP_4 (10 m%)

a) b)

c) d)

52 Chapter 4


A further increase towards 10 m% of SAPs is not ideal as the mixture becomes not

workable enough.

Figure 4.5. Amount of absorbed water due to the immersion with 4 m% of SAP

The graph of the figure 4.5 shows the behaviour of all SAPs with 4 m%, the values

obtained with SAP 1 are similar to the values using SAP 4, and values of the SAP 2 and SAP

3 are also similar. When the first group of SAPs (1 and 4) is used greater values of

absorption are reached, the absorption is three times higher than the absorption with

SAPs (2 and 3).

This behaviour follows the results obtained in the filtration test, as shows the

figure 4.1.d, the absorption in cement filtrate solution is higher for SAP 1 and SAP 4,

whereas for SAP 2 and SAP 3 the absorption is about half.

4.3.2 Study the percentage of voids

Using the values of the table 4.3 the percentage of voids was obtained according to

ASTM C642–13 standard. Figure 4.6 shows the percentage of voids in the four different

SAPs and also with the four different percentages of SAP, as well as the percentage of voids

of the reference.

While the percentage of voids using the Archimedes’ principle was not accurate

enough, the method proposed in the ASTM C642–13 standard was used. The reason of the

lack of accuracy was that during the manipulation of the specimens, a loss of water was

observed, mainly of the water in the open porosity of the external part and the water

swollen by the SAP of the specimens face.

The results of voids percentage obtained by the ASTM C642–13 standard were

presented in the figure 4.6.

0

20

40

60

80

100

120

140

160

180

0 8 16 24 32 40 48

We

igh

t (g

)

Time (h)

REF

SAP_1 (4 m%)

SAP_2 (4 m%)

SAP_3 (4 m%)

SAP_4 (4 m%)



Figure 4.6. Percentage of voids in different SAPs

From the results of the figure 4.6 it can be seen that the percentage of voids for the

dosage with 0.5 m% of SAP is similar for all SAPs, being higher for the SAP_4, which for all

the dosages have the similar behaviour as SAP_1, this was also seen in the absorption and

desorption test (figure 4.5). Studying the 4 m% of SAP, the specimens with this dosage

have a percentage of voids around 20 % that is little more than twice times the percentage

of voids that present the reference sample. The appearance of the samples seems adequate

in terms of strength since the edges of the samples remain unfragmented. For the higher

amount of SAP (10 m%) the percentage of voids is more than 3 times the percentage of

voids of the reference specimen, this becomes also in a loss in strength making the

specimens easily breakable.

4.3.3 Conclusions

Although during the drying stages the most appropriate specimens seemed to be

those with 10 m% of super absorbent, during the immersion stage the specimens which

were able to absorb more water were those with 4 m% of superabsorbent.

The most appropriate SAP percentage was 4 m%. The behaviour of

superabsorbent SAP 1 and SAP 4 on one hand, and on the other SAP 2 and SAP 3 are

similar. Since the super absorbents 1 and 2 are not commercialized the amount of material

that the company provide was not sufficient to manufacture all the required specimens for

the algae fouling test.

Then, it is decided to manufacture only specimens with SAP 3 and SAP 4 using two

types of dosage, first the standardised one used in all the test of absorption and desorption

and a second one with higher porosity.

4.4. CHARACTERIZATION OF THE BIO-RECEPTIVITY SPECIMENS

This section shows the results of the porosity of the selected specimens

manufactured to study the bio-receptivity. The selected SAPs were SAP 3 and SAP 4 with a

8.6 8.6 8.6 8.6 10.5 11.5 10.8 12.0

14.1 12.2 11.8

12.6

23.5 21.6

17.5 22.0

29.4 32.1

39.6

29.9

0

10

20

30

40


Pe

rce

nta

ge

of

vo

ids

[%]

REF

0.5 m%

1 m%

4 m%

10 m%

54 Chapter 4


percentage of 4 m%. Due to the fact that these specimens were manufactured in the

installations of the company ESCOFET, the owner of the moulds, and as the materials were

weighted in kg, at the end the m% was slightly different. The values of the m% of SAP and

the corresponding water-to-cement ratios are presented in table 4.5.

Table 4.5. Corresponding water-to-cement ratios (additional, total and effective) of the specimens

Code m% SAP [kg] (w/c)add [-] (w/c)tot [-] (w/c)eff [-]

REF_NORM (C1) - - 0.667

0.667 SAP_3_NORM (V1) 4.07 0.991 0.325

SAP_4_NORM (T1)

REF_POROSITY (C2) - - 0.674

0.674 SAP_3_ POROSITY (V2) 4.45 1.011 0.337


Table 4.5 shows that the effective ratio is almost the same, however, the

standardised specimens have a higher amount of additional water for SAP, so this will

have an effect in the structure of the specimens, making the internal structure more

porous.

A typical pore size distribution for hardened cement encompasses a large range,

extending from about 10 μm to as small as 0.5 nm or less in diameter, a classification is

shown in table 4.6. The larger pores, ranging from 10 μm to 50 nm, are the residual

unfilled spaces between cement grains, earlier defined as capillary pores. The fine pores,

ranging forma approximately 10 nm to 0.5 nm, are called gel pores since they constitute

the internal porosity of the C-S-H gel phase. While this is certainly a useful distinction, it

should be kept in mind that the sizes of capillary and gel pores overlap, and the spectrum

of pore size in a cement paste is continuous. Internal features with dimensions of 0.5 nm

or smaller are formed by the interlayer spaces of C-S-H gel. Water located in these features

is not in the liquid, so these are not true pores as defined for cement paste. Alternatively,

according to IUPAC an easier way to classify pores is as micropores with size less than 2

nm, mesopores between 2 – 50 nm and macropores higher than 50 nm.

The porosity is one of the main parameters that influencing in the bio-receptivity,

for this reason the distribution and the size of the pores of the specimens defined to study

the bio-receptivity is determined. In order to study these parameters, as it is defined in the

table 4.5 specific techniques are necessary to determine the different size pores, dynamic

vapour sorption (DVS) and mercury intrusion porosimetry (MIP) were performed. An

accurate study of the surface pores was performed to the specimens in order to determine

the larger pores, the biggest pores are due to the aggregates size and the cement paste

content whereas the smaller pores are responsible of the w/c ratio. Additionally, with the

study of the surface pores it is possible to determine the open porosity of the surface,

these pores are favourable for the growth. The results of the DVS, MIP test and the surface

pores are presented in the following sections.



Table 4.6. Classification of pores and features in concrete (Mindess et al., 1996)

Type of pore Description Size Water Technique

Capillary pores

Large 10 μm – 50 nm Evaporable

Bulk water SEM(a), OM(b)

Medium 50 – 10 nm Evaporable

Moderate menisci SEM

Gel pores

Small

capillary

pores

10 – 2.5 nm Evaporable

Strong menisci

DVS(c), MIP(d),

IS(e)

Micropores 2.5 – 0.5 nm

Non-evaporable

No menisci

Intermolecular interactions

DVS, MIP, IS

Interlayer

spaces Structural < 0.5 nm

Non-evaporable

Ionic/covalent bond DVS, Thermal

(a)SEM: scanning electron microscopy; (b)OM: optical microscopy; (c)DVS: dynamic vapour sorption; (d)MIP:

mercury intrusion porosimetry; (e)IS: impedance spectroscopy

4.4.1 Dynamics water vapour sorption isotherms

Taking into account that the main function of the SAPs in the specimens is to

increase the capacity of absorb and retain water, water vapour sorption measurements

constitute an essential tool to characterize the capacity of absorbing and desorbing.

Figure 4.6 describes the change in mass in each step of the relative humidity

percentage, the value at the end of each increment of RH gives a point for the isotherms of

sorption and desorption, with these points the curves (isotherms) of figure 4.7 can be

drawn.

Figure 4.7. a) DVS change in mass at each RH and b) isotherm plot of the specimen V1

The water vapour sorption curves for the dynamic water vapour measurements

are shown in figure 4.8. The curves show the mass water content as a function of the

relative humidity.

0

20

40

60

80

100

0

1

2

3

4

5

0 400 800 1200 1600

Ta

rge

t R

H [

%]

Ch

an

ge

In

Ma

ss [

%]

- D

ry

Time [mins]

dm - dry

Target RH

0

1

2

3

4

5

0 20 40 60 80 100 Ma

ss w

ate

r co

nte

nt

[%]

Relative humidity [%]

Sorption

Desorption

a) b)

56 Chapter 4


Figure 4.8. Dynamic water vapour sorption results.

As expected from Snoeck et al. 2014, since the specimens were carbonated the

slopes of the isotherms are almost linear until high relative pressures. This is because the

degree of carbonation affects directly reducing the porosity of the specimens; however,

the carbonation is necessary for the bio-receptivity.

The water uptake during the first part is lower, been from 40% thereafter of the

curve for higher relative pressures steeper. The sample T2 has the smoothest slope by

contrast the V1 has the steeper slope been this steeper with higher RH. It can be observed

from figure 4.8 that the slope behaviour of the specimens V2 and C2 is almost the same

and that the specimens with index 1 are always above the specimens with index 2. The

reason of this is, although the effective water-to-cement relation used in the specimens 1

is slightly smaller ((w/c)eff,1 = 0.667) than in the specimens 2 ((w/c)eff,2 = 0.674), and from

this the specimens 1 might be denser, the additional water in the cases 1 have more

additional water. The porosity is not only influenced by the w/c ratio but also by the

amount of additional water used due to the SAP, as the higher the relation w/c more

porosity and more additional water for the SAP is, the more porosity in the studied case

where additional water added for specimens with index 1, which curves has the higher

values.

4.4.2 Amount and distribution of pores calculated by means of the BJH and

DR methods

The mesopore size distributions have been calculated by the BJH method applied

to the absorption branch and the obtained curves of the figure 4.9, which show the pore

size distribution as a function of the pore diameter, with V the volume of the pores and D

the diameter.

0

1

2

3

4

5

0 10 20 30 40 50 60 70 80 90 100

Ma

ss w

ate

r co

nte

nt

[%]

Relative humidity [%]

C1 V1 T1 C2 V2 T2



Figure 4.9. Calculated microstructure with the BJH method.

The curves of the figure 4.9 present a maximum around 5–6, this confirm that the

porous network of the materials is mainly formed out of narrow mesopores (dp ~ 5–6

nm), however the specimen V1 has this maximum shifted towards dp ~ 16 nm but does

show approximately the same amount around 5–6 nm.

The higher amount of mesopores is presented by the V1, which has approximately

the same amount of micropores than C2, V2 and T2. By contrast, C1 and T1 have higher

amount of micropores however, they have a low value of mesopores.

The C-S-H gel amounts, the SBET-values and the volume of meso and micropores are

presented in the table 4.7.

Table 4.7. C-S-H amount and comparison between the textural parameters calculated by water sorption (~20 ), specific surface area SBET, mesopore and micropore volumes.

C-S-H gel amount [mm3/g]

Specific surface area (SBET) [m2/g]

Mesopore volume

[mm3/g]

Micropore volume

[mm3/g]

C1 49 38 35 10

V1 43 34 45 9

T1 46 36 31 10

C2 38 28 29 8

V2 38 29 29 8

T2 32 24 22 7

From the figure 4.9 and the table 4.6 it can be seen that the micropore volume

calculated with DR theory is much lower compared to the mesopore volume calculated

with BJH, this is an intrinsic property of cementitious materials.

The C-S-H gel amount, also given in table 4.6, reflects the gel pores which are

mostly seen when using the water sorption technique. The values should be lower if the

water-to-cement lowers however in this case, as it is explained in the other sections, the

0

10

20

30

40

50

0.001 0.01 0.1

dV

/d(l

og

D)

[mm

³/g

]

Pore diameter [µm]

C1 V1 T1 C2 V2 T2

58 Chapter 4


specimens with index 1 have more additional water and due to this they are more porous.

And, the specimens with index 2 are denser, as it could be seen from the results of the

table 4.6.

The SBET follows the same trend as the C-S-H gel amount. The values are range from

24 to 38 m2/g, which are low values, but typical for carbonated specimens.

4.4.3 Mercury intrusion porosimetry

The Mercury intrusion porosimetry test gives the large capillary pores. The figure

4.10 and 4.11 display the intrusion curves and the porosity distribution, respectively.

Figure 4.10. Cumulative intrusion volume [mm3/g]vs. Pore diameter curves

As denser the samples it is expected the cumulative intrusion curve to be more flat

for larger pore sizes, this is observed in figure 4.10, specimen C1 has almost a linear

behaviour with pore sizes higher than 1 μm.

Form figure 4.10 it is observed that for smaller pore sizes than 1 μm, specimens

T1, C2, V2 and T2 have the same distribution, however for larger pore sizes than 1 μm, the

curves are following different behaviours. The larger pores are important in specimens V1

and V2, and are near zero for the reference specimens (C1 and C2) since these specimens

are not containing SAPs.

Figure 4.11 shows that all the specimens have an absolute maximum around 0.5 –

0.7 μm, and after that point there is a decrease, meaning a decrease of the total porosity

for higher diameters. However, some specimens have smooth extra maximums, in small

pore sizes and also in larger pores sizes. The specimen T1 has a notable peak also around

0.07 μm, although specimens V1 and V2 have an increase of the larger pore sizes, between

10 – 100 μm.

0

20

40

60

80

100

120

0.001 0.01 0.1 1 10 100

Cu

mu

lati

ve

in

tru

sio

n

vo

lum

e [

mm

3/

g]

Pore size [μm]

C1 V1 T1

C2 V2 T2



Figure 4.11. Incremental intrusion vs. Pore diameter curves

As a summarizing figure, the different percentages of the pore size are presented in

figure 4.12, displaying the percentages for the different pore size ranges.

Figure 4.12. Percentage of pores of the following ranges: > 10 μm; 1 – 10 μm; 0.1 – 1 μm; < 0.1 μm

The most representative pore size falls within the range of 0.1 – 1 μm being around

50%. The percentage of the smallest range is around 25% for all the samples, unless for

sample C1 that has higher percentage of small pores. The range of higher pores (> 10 μm)

is significant for the specimens V1 and V2, by contrast the other do not have a significant

percentage of pores in that range.

4.4.4 Air-void analysis

The air voids analysis and more specifically spacing factor in conventional concrete

was extensively investigated since it has an important influence in the resistance to

freeze/thaw cycling. The spacing factor is roughly ranging between 0.02 and 0.50 mm,

however, a distinction has to be made between accidentally entrapped air voids with

random size and shaping, and the deliberately entrained air bubbles which are much

smaller and are distributed uniformly through the concrete paste (Elsen et al. 1994).

0

10

20

30

40

50

60

70

80

90

0.001 0.01 0.1 1 10 100

dV

/dlo

g(D

)

Pore size [μm]

C1 C2

V1 V2

T1 T2

0

10

20

30

40

50

60

70

80

90

100

C1 V1 T1 C2 V2 T2

Re

lati

ve

vo

lum

e o

f p

ore

s [%

]

> 10 μm

1 - 10 μm

0.1 - 1 μm

< 0.1 μm

60 Chapter 4


The porosity of the surface, also called open porosity as it is a small hole on the

surface, is an important factor for the bio-receptivity. The fact is that the porosity of the

surface, which is usually caused by air voids, and in this case mainly caused by a SAP

particle, this open porosity allows the water to come inside and to be absorbed by the SAP.

The surface porosity is measured with the Rapid Air void test which studies diameters

larger than 2 μm.

Table 4.8. Air content [%] and spacing factor [mm] given by Rapid Air test

Air Content [%] Spacing Factor [mm]

MOULD FACE AIR FACE MOULD FACE AIR FACE

C1 0.77 0.65 0.253 0.253

V1 3.84 20.84 0.623 0.223

T1 1.01 15.67 0.645 0.306

C2 2.32 2.31 0.331 0.270

V2 6.91 13.95 0.282 0.182

T2 3.03 16.82 0.431 0.255

Figure 4.13.a presents the results of the air content and in any case this percentage

is larger than 25%. Figure 4.13.b displays the spacing factor in mm and this factor is lower

than 0.7 mm, it should be taken into account that the studied surface is a square of 8x8

cm2.

Figure 4.13. Measurements of mould face and air face of: a) Air content [%] and b) spacing factor

[mm]

Comparing the results of the figure 4.13 the mould face with the higher amounts of

air content are V1 and V2, this corresponds with the specimens with higher amounts of

larger pore sizes obtained with MIP (figure 4.12). If the air face is analysed, the specimens

with SAP (V1, T1, V2 and T2) have more air content on that face, since the previously

swollen SAP were in that place. These specimens have air contents between 15 – 20 %,

this was shown also in the percentage of voids (figure 4.6). The percentage of voids was

affected mainly for the external porosity of the air face where the voids due to the SAP are

located.

0.00

5.00

10.00

15.00

20.00

25.00

MOULD FACE AIR FACE

Air

co

nte

nt

[%]

C1 V1 T1

C2 V2 T2

0.000

0.100

0.200

0.300

0.400

0.500

0.600

0.700

MOULD FACE AIR FACE

Sp

aci

ng

fact

or

[mm

]

C1 V1 T1

C2 V2 T2

a) b)



Studying the spacing between pores, the air face has more equally distribution

comparing all the specimens on this surface between pores. And, comparing the surface

that touches the mould face the spacing is higher for the specimens V1, T1 and T2.

Analysing the differences between the mould face and the air face for the same

specimens, it can be seen that for the reference specimens (C1 and C2) the value of air

content is approximately the same in both faces as well as the spacing factor. The SAPs

have a larger influence in the open porosity of the air face since the SAP is not intersected

at the mould face, nevertheless is intersected at the air face. The spacing factor in the air

face is twice the spacing factor in the mould face for the specimens (V1 and T1) and this

relation is less in the case of (V2 and T2) but remains higher for the air face.

The diameter of the open pores is also different in the mould face compared to the

one in the air face, some examples of the specimens with SAPs are shown in the figure

4.14.

V1

T2

Figure 4.14. Pore size (left: mould face and right: air face)

62 Chapter 4


Bio-receptivity evaluation under laboratory conditions 63


CHAPTER 5

BIO-RECEPTIVITY EVALUATION UNDER

LABORATORY CONDITIONS

5.1. INTRODUCTION

The main goal of this chapter is study the bio-receptivity of the selected specimens.

The selection of these specimens is the result of the chapter 3 and 4 where the main

parameters to promote the bio-receptivity, such as higher absorbency, were studied. To

determine the capacity of fouling of each specimen, an accelerated laboratory test was

carried out.

To quantify and analyse the evolution of the fouling some methods proposed in the

literature were used. Since image analysis and colorimetric measurements have been

corroborated as good methods by (Tiano et al., 1995; Pietro et al., 2004; Alum et al., 2009;

De Muynck et al., 2009; Escadeillas et al., 2009; Miller et al., 2010a, 2010b; Manso et al.,

2014) in this study the two methods mentioned were used.

The experimental program was mainly carried out in two different laboratories:

the Magnel Laboratory for Concrete Research (UGent) where accelerated algae fouling test

was performed and the Laboratory of Microbial Ecology and Technology, LabMET (UGent)

where the algae cultures were grown.

64 Chapter 5


5.2. MORTAR SPECIMENS

Since the main research parameter is the superabsorbent polymer, the amount of 4

m% of the two selected SAPs was used. The study was carried out with two set of

specimens, the first one using the proportions of a standardised paste which have the

index 1 in the code. The second set was made using different dosage in order to obtain

high porosity specimens, these have the index 2 in the code. The index V is related to

superabsorbent Virgin also called SAP 3 and the index T is related to Terracottem, SAP 4.

Table 5.1. Selected specimens to study the bio-receptivity

Code Cement

[kg]

Sand

[kg]

Water

[kg]

SAP

[kg]

Additional

water [kg]

REF_NORM (C1)

12.3 36.9

(standard) 8.2

- -

SAP_3_NORM (V1) 0.5 4.0

SAP_4_NORM (T1)

REF_POROSITY (C2)

8.9 35.9

(0-5mm) 6.0

- -

SAP_3_ POROSITY (V2) 0.4 3.0


5.3. ACCELERATED ALGAE FOULING TEST

The accelerated algal fouling test was developed at the Magnel Laboratory for

Concrete Research of Ghent University (De Muynck et al., 2009). This modular test set-up

allows evaluating simultaneously different materials towards algal fouling. The test

consists of inclined (45°) and independent PVC compartments where the samples are

placed (see figure 5.1 and figure 5.2). Then the test is composed by two periods that

started every 12 hours and ran for 90 minutes. Every day there was 12 hours day and

night regime, which started simultaneously with the 90 minutes run-off periods (De

Muynck et al., 2009). During the day regime, light was provided by means of Sylvania

Grolux 30 W lamps. The temperature and relative humidity ranged were 25°C (day) – 22°C

(night) and 82 % (day) – 90 % (night).

Figure 5.1. Schematic setup used for the accelerated algal fouling test

Air pump

Sylvania Grolux 30 W lamps

Reservoir

Aquarium pump

Plastic gutter

Sprinkling rail



Figure 5.2. Accelerated algal fouling test

In order to carry out the test the algae specie used was Chlorella vulgaris fo. viridis.

The strain (number CCAP: 211/12) was obtained from the Culture Collection of Algae and

Protozoa (CCAP) from Scottish Marine Institute, Oban, Argyll, UK. To grow up the cultures

the stock solution presented in the table 5.2 should be first made. To make 1 L of fresh

medium from stock solution the volumes presented in table 5.3 were used. To start

growing the algae 15.0 g of Bacteriological Agar were added to 100 mL of fresh medium

(see figure 5.3). After 9 days, the first growing culture was added to 1 L fresh medium to

start the algal fouling test. Each week 150 ml of the old culture was added to the 1 L new

fresh medium (see figure 5.4), the culture was continuously exposed to light with an

intensity of approximately 40 μmol·m-2·s-1 on a rotator shaker at 120 rpm.

Figure 5.3. a) 15.0 g of Bacteriological Agar; b) First growing batch

Figure 5.4. One week old culture and new culture

a) b)

66 Chapter 5


Table 5.2. Stock solution

Stock solution in g / 1000 ml water

[1] 75.0 g NaNO3

[2] 2.5 g CaCl2·2H2O

[3] 7.5 g MgSO4·7H2O

[4] 7.5 g K2HPO4·3H2O

[5] 17.5 g KH2PO4

[6] 2.5 g NaCl

[7] Trace element solution ((*)see below)

[8] Vitamin B1

0.12 g Thiaminhydrochloride in 100 ml distilled water. Finally, filter through

a sterile filter.

[9] Vitamin B12

0.10 g Cyanocobalamin in 100 ml distilled water, 1 ml of the solution is taken

and 99 ml distilled water are added, finally filter through a sterile filter.

(*) To 1000 ml of distilled water 0.75 g Na2EDTA and the minerals in exactly

the following sequence are added:

97.0 mg FeCl3·6H2O

41.0 mg MnCl2·4H2O

5.0 mg ZnCl2

2.0 mg CoCl2·6H2O

4.0 mg Na2MoO4·2H2O

Table 5.3. Final medium solution

Final medium (for 1 L)

[1] 10.0 ml

[2] 10.0 ml

[3] 10.0 ml

[4] 10.0 ml

[5] 10.0 ml

[6] 10.0 ml

[7] 6.0 ml

[8] 1.0 ml

[9] 1.0 ml

For the accelerated algae fouling test a concentration of cells/ is needed.

The cell counting was performed using a Zeiss Axioskop II plus light microscope (Zeiss,

Germany) and a Neubauer chamber (see figure 5.5 and 5.6). Despite the fact of the recent

technical development of scientific laboratories, the Neubauer chamber remains the most

common method used for cells counting around the world (Bastidas). To start the



counting 10 μl of one week old culture was picked with a micropipette tip and then to the

Neubauer chamber was brought making sure that the liquid enters between the Neubauer

chamber and the glass cover. When the camber has been loaded, the microscope can be

focus the squares of the Neubauer chamber (see figure 5.7) will be counted. Since there

are different counting protocols the following rule was followed: “cells touching the upper

and left limits should be counted, unlike cells touching the lower and right limits which

should not be taken into account” (see figure 5.7). After counting the number of cells of

each square the concentration (cell/ml) is determined using the following equation:

Figure 5.5. Light microscope Zeiss Axioskop II plus

Figure 5.6. Neubauer chamber

If the determined volume corresponded to cells, the culture medium to

run-off the test could be prepared. The culture medium to run-off the accelerated algal

fouling test consisted in 1 L of mineral drinking water, the corresponding volume of one

week old culture with a final concentration of cells/L and 2 ml of the final

solution (only using the components [1] to [7]) and 0.1 ml of each vitamin (component [8]

and [9]). Every week, the contents of the reservoirs were replaced by new algal cultures

after cleaning of the reservoirs.

[ 5. 1 ]

Cover glass

Filling notch Counting chambers

Overflow area

Mounting support

68 Chapter 5


Figure 5.7. Count in a Neubauer chamber big square

5.4. EVOLUTION AND QUANTIFICATION OF BIOFOULING

To define the area covered with algae different test were carried out each week.

The degree of fouling was evaluated by means of colorimetric measurements and image

analysis. Due to the fact that the measurements are sensitive to the moisture content of

the specimens (De Muynck et al. 2009; Manso et al., 2014), the specimens were studied 10

hours after the irrigation occurred, and with this the same moisture content is ensured. To

evaluate the specimens in week zero, the test was run only with mineral water one day

before the measurements.

Colorimetric measurements were performed by means of an X-Rite SP60

colorimeter (X-Rite, USA) with an 8 mm aperture (see figure 5.8). On each specimen, four

measurements were taken at the same positions (near each corner around 1cm from the

edges). The CIELab system defines the colour of an object based on two chromaticity

coordinates, a* (green-red components) and b* (blue-yellow components), and lightness

factor L* (black-white component). The reflectance (%) for visible wavelengths from 400

nm until 700 nm every 10 nm also was given by the colorimeter.

Figure 5.8. a) Three-dimensional CIELAB colour space (Li et al., 2005); b) X-Rite SP60 colorimeter

L* = 0 (Dark)

L* = 100 (Light)

+ a* (Red)

- a* (Green) +b* (Yellow)

- b* (Blue)

a) b)



Chlorella vulgaris characteristic pigments are chlorophyll a, chlorophyll b and

carotenoids and their maximum absorbance peak are localised at around 430 nm and 670

nm for chlorophyll a, around 450 nm and 640 nm for chlorophyll b and around 460 nm for

carotenoids as shown in figure 5.9. For that reason, drops in reflectance at these specific

wavelengths should be expected when the specimens are fouled.

Figure 5.9. Absorption spectra of Chlorophyll a, b and carotenoids (UIC, 2014)

From the colorimeter data, L*, a*, b* and reflectance, total colour difference (ΔE*),

chromatic variations (ΔC*), changes in hue (ΔH*) and fouling intensity (FI, %) were

calculated using the following equations [5.2], [5.3], [5.4] and [5.5] (De Muynck et al.,

2009; Ferri et al., 2011; Tran et al., 2012; Manso et al., 2014):

and represents the reflectance of the specimens at wavelength of

670 nm and 700 nm and t represents the time (weeks). The measurements were taken

with the same conditions around 10 hours after the rain.

Afterwards, for the image analysis, the specimens were scanned with a Canon

Scan 3000F scanner and after that ImageJ software was used for the image analysis and to

process the obtained images. De Muynck et al. (2009) proposed a quantification of the

[ 5. 2 ]

[ 5. 3 ]

[ 5. 4 ]

[ 5. 5 ]

Chlorophyll a

Chlorophyll b

Carotenoids

Wavelength of light [nm]

A

mo

un

t o

f li

gh

t a

bso

rbe

d

70 Chapter 5


area covered by algae by means of a threshold analysis on a* (green to red axis) and b*

(blue to yellow axis) coordinates of the CIELab colour space. With the purpose of

determine the appropriate correlation between the real sample and the processed images

as a result of threshold operation on a* and b* axis, both processes were done and

compared. Figure 5.10 shows the result of the processed images and by visual comparison

it is concluded that the better correlation is with the threshold operation on a* axis.

Figure 5.10. Correlation between a) the real sample the b) threshold operation on the a* axis and c) threshold operation on the b* axis.

The pixels with values lower than 120 (0-256) were considered as fouled and

changed to black and the values greater than 120 changed to white and considered as

unfouled.

On the other hand, the surface open pores were analysed by means Leica S8 APO

microscope (see figure 5.11) in order to know in more detail which is the behaviour of the

colonization around the pores and inside them.

Figure 5.11. Leica microscope

Another method for biomass quantification was used by Manso et al. in 2014, this

non-destructive method comprises the measurement of chlorophyll fluorescence by PAM-

fluorometry was proposed by Eggert et al. in 2006 but according to Manso et al. the

quantification after reach a certain coverage biofouling the method was not useful, for this

reason is not used in the present work.

a) b) c)



5.5. RESULTS OF ACCELERATED ALGAE FOULING TEST

5.5.1 Colorimetric measurements

Every week four measurements to each of the three specimens were done.

Consequently, the results of the study are the average between twelve measurements.

The colonization of the specimens has heterogeneity around the surface, so comparing the

three studied replicates of each specimen there was also heterogeneity on the results. But

there was also heterogeneity comparing the different parts of one sample. Figure 5.12

shows the three replicates of one specimen with the four points where the measurements

were taken. In this case the specimen was colonized homogeneously but heterogeneity

was found comparing the replicates. The heterogeneity in one sample was also possible, as

it can be seen in figure 5.14.

Figure 5.12. Heterogeneity between replicates of the same specimen

In figure 5.13 the reflectance of each replicate is shown as well as average. The

curves of the replicates are drawn with the average of the measurements in the four

points, and the average reflectance is the average between the three curves (the average

between twelve measurements).

0

2

4

6

8

10

12

14

16

18

20

22

400 500 600 700

Re

fle

cta

nce

(%

)

Wavelength (m]

Replicate 1

1 2 3 4

0

2

4

6

8

10

12

14

16

18

20

22

400 500 600 700

Re

fle

cta

nce

(%

)

Wavelength (nm)

Replicate 2

1 2

3 4

0

2

4

6

8

10

12

14

16

18

20

22

400 500 600 700

Re

fle

cta

nce

(%

)

Wavelength (nm)

Replicate 3

1 2

3 4

1 2

4 3

1 2

4 3

1 2

4 3

72 Chapter 5


Figure 5.13. Reflectance of each replicate as well as the average of them

Figure 5.14. Heterogeneity in fouling of a replicate: a) sample T2 after 8 weeks b) reflectance

Figure 5.14 shows one replicate of the sample T2 after 8 weeks of algal fouling. As

it can be seen the specimens is not homogeneously fouled. The upper part of the sample,

near the second point, is greener compared to the other parts. This zone corresponds to

the zone where the sample has more open porosity.

From now on the measurements presented in the figures are the average between

the twelve points. As it was mentioned the measurements were done every week despite

that only some weeks are plotted in the figure 5.15 (week 0, 1, 2, 4, 6, 8 and 10) in order to

facilitate the interpretation of the data. Nevertheless, to study in more detail and make a

comparison between specimens in the same week, more reflectance graphs of week 0, 6, 8

and 10 are presented in figure 5.16. The first week and the last few weeks have been

chosen in order to compare the evolution, due to the fact that the colonization is more

significant in the lasts weeks, as it can be seen in the figure 5.15 the curves in the lasts

weeks have more drops in reflectance meaning higher colonization.

0

2

4

6

8

10

12

14

16

18

20

22

400 500 600 700

Re

fle

cta

nce

(%

)

Wavelength (nm)

Replicate 1 Replicate 2

Replicate 3 Average

0

2

4

6

8

10

12

14

16

18

20

22

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]

1 2 3 4

1 2

4 3

a) b)



Figure 5.15. Reflectance curves of specimens: a) C1; b) C2; c) V1; d) V2; e) T1 and f) T2

0

10

20

30

40

50

400 500 600 700

Re

fle

cta

nce

[%]

Wavelength [nm]

Week 0 Week 1 Week 2


Week 10

0

10

20

30

40

50

400 500 600 700

Re

fle

cta

nce

[%]

Wavelength [nm]



Week 10

0

10

20

30

40

50

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]



Week 10

0

10

20

30

40

50

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]

Week 0 Week 1 Week 2 Week 4 Week 6 Week 8 Week 10

0

10

20

30

40

50

400 500 600 700

Re

fle

cta

nce

[%]

Wavelength [nm]


0

10

20

30

40

50

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]


a) b)

c) d)

e) f)

C1 C2

V1 V2

T1 T2

74 Chapter 5


It should be taken into account that the scale of the graphs of figure 5.16 is not

equal, for the purpose of facilitating the interpretation of the data.

Figure 5.16. Reflectance curves for all the specimens: a) week 0; b) week 6; c) week 8 and d) week 10

The first measurement, week zero, as it was mentioned was done before one day of

running test without algae (only with water). The results presented in the figure 5.16.a

show the curves without drops in any wavelength, and without overlap as could be

expected, this is because the initial colour of the specimens are not the same between the

studied specimens.

After 6 weeks of test, the curves of reflectance have drops being more pronounced

for the specimen V2 (see figure 5.16.b). And, as the weeks go by, the curves are adopting

the shape of a colonized specimen (with drops near 450 and 670 nm). Figure 5.16.c

displays the results of the week 8, where it can be seen two groups of curve, one formed by

specimens V2, C2 and V1 and the second formed by T1, T2 and C1. The first group has the

curves in the lower part with less reflectance and more pronounced drops, meaning more

0

10

20

30

40

50

400 500 600 700

Re

fle

cta

nce

[%]

Wavelength [nm]

C1 V1 T1

C2 V2 T2

0

5

10

15

20

400 500 600 700

Re

fle

cta

nce

[%]

Wavelength [nm]

C1 V1 T1

C2 V2 T2

0

5

10

15

20

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]

C1 V1 T1

C2 V2 T2

0

5

10

15

20

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]

C1 V1 T1

C2 V2 T2

a) b)

c) d)



colonization. Whereas, in the last week of the test (figure 15.6.d) the curves of the

specimens V2 and C2 are almost equal and being in the lower part of the graph.

The pioneer specimens from the beginning of the test was V2, followed by the

specimen C2, T1, T2 and V1. The specimen C1 as it can be seen in all the graphs of figure

5.16, has no drops at the wavelength of 670 nm, this will be analysed in more detail in the

figure 5.16 with the fouling intensity (%) which is the difference between the wavelength

700 nm and 670 nm in different weeks (see equation [5.5]).

Besides the reflectance, other parameters are obtained from the colorimetric

measurements are presented in table 5.4. L*, a*, b* and total colour difference (ΔE*),

chromatic variations (ΔC*), changes in hue (ΔH*) calculated with the equations [5.2], [5.3]

and [5.4]. The variation in parameters L* and a* should be studied since the progressive

decrease of this values indicate more fouling. For the parameters, ΔE*, ΔC* and ΔH*, larger

values denote more colonization.

Table 5.4. Colorimetric measurements

week L* a* b* ΔE* ΔC* ΔH*

C1 0 66.81 ± 1.07 -0.57 ± 0.03 3.48 ± 0.15

10 41.34 ± 3.08 1.39 ± 1.55 13.17 ± 0.28 27.32 9.72 1.81

V1 0 64.40 ± 2.03 -0.61 ± 0.09 3.67 ± 0.45

10 40.28 ± 3.27 0.20 ± 1.33 14.80 ± 1.19 26.57 11.07 1.32

T1 0 68.99 ± 2.41 -0.56 ± 0.09 4.53 ± 0.80

10 40.28 ± 3.19 -1.37 ± 1.82 17.04 ± 2.14 31.41 12.53 0.37

C2 0 72.82 ± 0.56 -0.71 ± 0.05 4.68 ± 0.65

10 36.01 ± 2.03 -3.09 ± 0.55 14.29 ± 2.06 38.12 9.89 0.51

V2 0 72.59 ± 2.89 -0.74 ± 0.12 4.20 ± 0.99

10 35.36 ± 2.64 -3.52 ± 0.85 15.34 ± 2.00 38.96 11.48 0.42

T2 0 67.24 ± 4.06 -0.48 ± 0.15 4.26 ± 0.82

10 41.17 ± 0.09 -0.54 ± 0.68 17.32 ± 1.60 29.16 13.04 0.70

Hence, the larger decrease in L* is shown in the specimen V2 followed by C2. In

this sense, this specimens also have larger values in the ΔE*, ΔC*, ΔH* parameters. The

specimen C1 has no larger variations in the a* values, as corresponds with the analysis

above (reflectance curves) this is the specimen with less fouling.

Subsequently, the fouling intensity was obtained with the equation [5.5], as the

difference between the reflectance in wavelength 700 nm and 670 nm (see figure 5.17),

and the results are presented in figure 5.18.

76 Chapter 5


Figure 5.17. Representation of the fouling intensity [%]

Figure 5.18. Evolution over time of fouling intensity [%] for all the specimens

Figure 5.18 displays the evolution over time of the fouling intensity, initial flat

slope is observed, where the growing was slow, and from one point the slope becomes

steeper and the growing was faster. The point at which a change in slope is observed

depends on the specimen, it can be observed that specimen V2 has this initial slope

steeper than the other specimens and it changes the 4 week. By contrast, the other

specimens have almost the same slope until the 4 week but this is so flat. From the third

week the specimen T1 starts to have more fouling intensity and the sample C2 has this

change in the week four. The other three specimens, C1, V1 and T2, have this point in the

week 6. Finally, as the other sections conclude the specimen with higher fouling is V2,

nearly followed by T1 and C2.

0

5

10

15

20

400 500 600 700

Re

fle

cta

nce

[%]

Wavelength [nm]

V2 C1

0

1

2

3

4

5

6

7

0 2 4 6 8 10

Fo

uli

ng

inte

nsi

ty [

%]

Time [weeks]

C1 V1

T1 C2

V2 T2

Fouling intensity

Fouling intensity



5.5.2 Image analysis

Using the software ImageJ and with the scanned specimens the image analysis was

done. Figure 5.19 shows the evolution of the growing after 10 weeks and the fouled area

(%) is presented in figure 5.20. To calculate the fouled area the pictures were processed

(see figure 5.10), the pixels with values lower than 120 were considered as fouled and

with the histogram values the fouled area was determined.

Figure 5.19. Evolution of visual appearance of the specimens subjected to accelerated algal fouling test

From the evolution of visual appearance of the specimens it can be seen that at the

end of the test (after 10 weeks), all the specimens are colonized in varying degrees. The

specimens C2, T1 and V2 are the most colonized in visual appearance, corresponding this

with the conclusions of the other test performed.

Analysing the area of fouling which is related to the percentage of the surface

fouled, as it was observed in the figure 5.18 with the fouling intensity there is an increase

in the area of fouling from the week 6 forwards (see figure 5.20).

C1

C2

T1

T2

V1

V2

Week 1 Week 2 Week 4 Week 6 Week 8 Week 10

78 Chapter 5


Figure 5.20. Evolution over time of the fouled area [%] for all the specimens

As with the fouling intensity, the fouled area (figure 5.20) shows an initial pioneer

specimen V2 which from the first weeks had more fouled area. Then, a transition point

from where the area of fouling is increasing, related to the fouling area this point is from

week 5. It can be distinguished also two inflection points where the fouling are seems to

be reduced, these points were in the week 3 and week 5. This decrease of the growing

could be produced by blockages of the irrigation produced by the blockage of the little

holds on the sprinkling rail, this could happen someday however continuous inspections

during the week were done in order to avoid this problems. As a consequence during these

periods of time, the fouled area could not grow as fast as was expected.

5.5.3 Microscopic analysis

Additionally, microscopic analysis was performed to the samples in order to know

the effect of the SAPs and where the growing starts. Some images were taken with the

microscopy after 3, 7 weeks and at the end of the test.

Figure 5.21 and 5.22 show in more detail the evolution of the colonization in

specimen V2 and T2, where the pores were studied. During the first weeks (see figure

5.21.a and 5.22.a), the start of the colonization was observed mainly in the areas

surrounding the pores, especially at the lower part of the pores where the water with the

algae was stored. Since the specimens were place in the set-up inclined 45 degrees the

water was stored in the pores with SAP and by the effect of the gravity at the lower part of

the pore is where the water remains more time (see figure 8.23). This might be a reason of

the initial growing and the larger colonization in these parts.

The colonization of the surface of the specimens was initiated around the pores

and afterwards the smaller pores around were fouled, as it could be observed in the figure

5.21.b and 5.22.b. Finally, by the end of the test all the surface was fully colonized (figure

5.21.c and 5.22.c).

0

10

20

30

40

50

60

70

80

0 2 4 6 8 10

Are

a o

f fo

uli

ng

[%

]

Time [weeks]

C1 V1 T1

C2 V2 T2



Figure 5.21. Specimen V2: a) after 3 weeks, b) after 7 weeks and c) after 10 weeks

Figure 5.22. Pore of specimen T2: a) after 3 weeks, b) after 7 weeks and c) after 10 weeks

Figure 5.23. Pore of specimen V2: a) 2 mm view and b) 500 μm view

From this observation, the importance of the open porosity it is shown and also the

positive effect that have the SAPs, which allow the colonization near them. Looking at the

air content and spacing factor presented in the figure 4.13, and studying the results of the

mould face which is the face exposed to the test of all the specimens. The specimen with

more colonization (V2) is the one with more air content pores in the surface, and less

spacing factor only taking into account the specimens with a content of SAPs, otherwise

the specimens without SAP have less spacing factor since the air content is low. This

means, that the open porosity due to the SAP is roughly equally distributed around the

surface, allowing the water stored around the entire surface. Specimen T2 has also a large

value of air content but this is no equally distributed around the surface and the pores are

higher in diameter and isolated, allowing the colonization around the pore but this is

concentrated at the zone of the pore, producing a heterogeneous distribution of the

colonization on the surface.

80 Chapter 5


5.6. STUDY UNDER SPECIAL CONDITIONS OF ACCELERATED ALGAE

FOULING TEST

Parallel to the main accelerated algae fouling test, the same test under special

conditions was performed with the purpose of show the effectively of the superabsorbent

polymer. The test consists in the same procedure explained in the section 5.3, the same

set-up and algae specie was used. The only change that was implemented was that the

specimens instead of receive the rain each week during the 10 weeks of the test, only the

weeks odd were under rain conditions. The other weeks, the even weeks, were situated

under the light conditions but not under the rain.

The evolution and the quantification of biofouling were performed in the same way

as in the main test explained in the section 5.4. Each week colorimetric measurements

were done as well as the scanning of the specimens for the image analysis.

As was explained in the previous section, the results are sensible to the moisture

content, so in this case the measurements were done also 10 hours after the irrigation

occurred. For this reason, the last day of the dry week the specimens were placed again in

the set-up and before the measurement the specimens receive one rain of 90 minutes

during the night period before the measurements.

Comparison of the results between the main test and this under special conditions

is not directly, since the degree of moisture in the specimens of the main test will increase

as the weeks progress. It is possible to observe the evolution of the specimens and

compare the effect of long dry periods.

5.6.1 Results of the special accelerated algae fouling test

The results of the special accelerated algae fouling test are presented in this

section. The measurements performed in the odd weeks were before the rain week and

the measurements done in the even weeks were before a dry period with only one rain as

it was explained.

In this case the graphs with the reflectance curves of each specimen were not

presented, the reason is that the lines are so close and do not add relevant information for

the analysis, being the drops in wavelength only present at the last weeks. The behaviour

is the same as it was shown in figure 5.15 the reflectance curves are decreasing as the

weeks pass. In this case, the reflectance curves comparing all the specimens in the same

week are presented in figure 5.24.

Figure 5.24 presents the results of the reflectance curves of the even weeks (0, 2, 4,

6, 8 and 10). It should take into account that the scale of reflectance is not equal for all the

graphs presented in figure 5.24 to facilitate the interpretation of the results. It can be seen

that the curves are regular without drops until the week 6 when the drops started but the

fouling intensity is still insignificant until the week 8.



Figure 5.24. Reflectance curves for all the specimens, special conditions: a) week 0; b) week 2; c) week 4 d) week 6, e) week 8 and f) week 10

Table 5.5 presents the other parameters obtained with the colorimetric

measurements under special conditions.

0

10

20

30

40

50

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]

C1 V1 T1

C2 V2 T2

0

10

20

30

40

50

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]

C1 V1 T1

C2 V2 T2

0

5

10

15

20

25

30

35

40

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]

C1 V1 T1

C2 V2 T2

0

5

10

15

20

25

30

35

40

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]

C1 V1 T1

C2 V2 T2

0

5

10

15

20

25

400 500 600 700

Re

fle

cta

nce

[%

]

Wavelength [nm]

C1 V1 T1

C2 V2 T2

0

5

10

15

20

25

400 500 600 700

Re

fle

cta

nce

[%]

Wavelength [nm]

C1 V1 T1

C2 V2 T2

a) b)

c) d)

d) e)

82 Chapter 5


Table 5.5. Colorimetric measurements, special conditions

week L* a* b* ΔE* ΔC* ΔH*

C1 0 66.81 ± 1.07 -0.57 ± 0.03 3.48 ± 0.15

10 48.95 ± 6.72 1.89 ± 0.88 10.74 ± 1.06 19.44 7.38 2.07

V1 0 64.40 ± 2.03 -0.61 ± 0.09 3.67 ± 0.45

10 45.02 ± 1.60 1.90 ± 0.22 11.36 ± 0.93 20.99 7.79 2.16

T1 0 68.99 ± 2.41 -0.56 ± 0.09 4.53 ± 0.80

10 50.52 ± 1.89 2.39 ± 0.71 13.00 ± 1.49 20.53 8.65 2.35

C2 0 72.82 ± 0.56 -0.71 ± 0.05 4.68 ± 0.65

10 49.97 ± 1.09 2.12 ± 0.62 15.14 ± 1.13 25.29 10.56 2.46

V2 0 72.59 ± 2.89 -0.74 ± 0.12 4.20 ± 0.99

10 50.47 ± 0.52 1.83 ± 0.78 14.65 ± 2.08 24.60 10.50 2.36

T2 0 67.24 ± 4.06 -0.48 ± 0.15 4.26 ± 0.82

10 48.50 ± 0.86 1.39 ± 0.63 12.81 ± 1.64 20.69 8.60 1.63

As it was mentioned, larger values of ΔE*, ΔC* and ΔH*, denote more colonization.

In this case, the larger values are obtained in the same specimens V2 and C2. Being the

results of both specimens quite similar, it should be taken into account that these

specimens have similar initial values also, as a result of the similar surface initial colour.

During the week 8 some specimens start to present the drops between wavelength

of 670 nm and 700 nm (see figure 5.24), this is also shown in figure 5.25 were the fouling

intensity is presented.

Figure 5.25. Evolution over the time of the fouling intensity [%], special conditions

0

1

2

0 2 4 6 8 10

Fo

uli

ng

in

ten

sity

[%

]

Time [weeks]

C1 V1 T1

C2 V2 T2



Figure 5.25 presents picks in the results of the odd weeks and then the even weeks

there is a decrease of the fouling intensity. During the first half of the test, it was observed

that during the even weeks without rain the incipient growing gets dry becoming browner

during the dry weeks. At that time, the rain of the odd week reactivates the growing again.

The results of the fouling intensity corresponding to the special conditions give

approximately the same sequence of specimens as under main test. The specimen V2 has

the larger value of the FI and in this case, the T2 gets advantage of the T1 that in the

previous case has larger value.

Figure 5.25 also shows as in the previous section a point at which a change in slope

is observed in this case the point is week 8, instead of week 4 and the slope is less steep,

achieving a final value of fouling intensity less than 2%.

The image analysis was performed to the specimens but the results are not

relevant since the specimens achieve a low degree of colonization. Figure 5.26 presents

the final results of the specimens, so the visual appearance of the specimens after the

special condition algae fouling test was perform.

Figure 5.26. Visual appearance of the specimens after 10 weeks in special conditions (first line: C1, V1, T1; second line: C2, V2, T2)

84 Chapter 5


Conclusions 85


CHAPTER 6

CONCLUSIONS AND FUTURE PRESPECTIVES

6.1. GENERAL CONCLUSIONS

In this section the general conclusions are presented in response to the general

objectives defined in Chapter 1. Specific conclusion will be presented in the following

sections, linked with the specific objectives also presented in Chapter 1. Future lines of

research are suggested at the end of this chapter.

The main properties of the SAP obtained during the characterization reveal that

the behaviour of the new SAPs provided by the BASF company have similar behaviour as

the commercial SAP provided also by the BASF company and another studied

superabsorbent which is also commercial and called TerraCottem. These main behaviours

allow reducing the amount of total specimens to be studied and enable to use other dosage

to obtain more porous specimens.

The increase in the water retention of the specimens provided by the addition of

the superabsorbent polymers is interesting in order to provide the capacity of retaining

water to the specimen. However, not all the dosages are equally valid, as some show poor

strength or not enough capacity to absorb.

The specimens used for the bio-receptivity analysis are suitable for the

colonization, although the fouling degree achieved was not the same in all cases. Some

specimens were colonized easier than the others, achieving a better final result.

86 Chapter 6


6.2. SPECIFIC CONCLUSIONS

Several specific objectives are proposed in Chapter 1 for each of the subjects

studied. In response to these specific objectives, the contributions made are described in

detail in each respective chapter of this document. With the aim of providing a general

overview of the contributions, the main specific conclusions of each subject addressed in

this thesis are presented in the following paragraphs.

Water kinetics of mortars containing superabsorbent polymers

During the study and the characterization of the SAPs and the mortar with SAPs,

the first step was to define the appropriate mass percentage of SAP for the dosage.

Comparing the results and the degree of water absorbency it was concluded that the

specimens containing 4 m% of SAP were the most suitable, the reason is that 0.5 m% and

1 m% had no the increase of the absorption expected and the 10 m% had difficulties in the

workability and the final strength of the specimen.

Additionally, from the four initial SAPs studied two main behaviours were

observed. Two SAPs following one and the other two following the other behaviour. With

this, the SAPs to be studied in the bio-receptivity were reduced to two of them.

Finally, the most suitable dosage was defined with 4 m% of SAP and the SAPs used

in the bio-receptivity study were the commercials, SAP 3 with the commercial name Virgin

and SAP 4, called TerraCottem Universal.

Porosity of the bio-receptivity specimens

The porosity of the specimens was defined as the porosity is one of the main

parameters influencing the bio-receptivity. From the DVS and MIP tests, the

microstructure of the specimens could be defined. And, with the Air-void analysis the

surface porosity and the larger range of pores were studied. The specimens were studied

after the carbonation, in order to compare the specimens that will be used in the bio-

receptivity test. It is known that the carbonation affects the microstructure of the

specimens, nevertheless is necessary to allow the bio-receptivity.

From the DVS and MIP tests, it was observed that the microstructure of the

specimens manufactured with the goal of be more porous have a denser microstructure.

This is because the porosity was increased by using different sand grain size, and these

have the effect in the macrostructure. The microstructure is mainly governed by the

water-to-cement ratio and is similar in both cases. However, the additional water due to

the SAPs in the more porous specimens was increased having at the end a higher effective

water-to-cement ratio. Finally, the values of the porosity obtained with the test were low

but ranging in the normal values because the effect of the carbonation.

To study the macrostructure, the larger range of pore size given by the MIP test

were analysed and also the results from the Air-void test. By contrast, the Air-void analysis

Conclusions 87


concludes with the result expected during manufacturing the specimens. From the large

range of pores obtained with the MIP test (> 10 μm), it could be concluded that the

specimens containing the Virgin SAP has higher amount of this range of pores. This could

be explained as the average diameter of the Virgin SAP is smaller than average diameter

for the TerraCottem. Specimens with TerraCottem superabsorbent have large pore

diameter for this reason, and this is too large to be measured by the MIP test.

The air-void test concludes with similar results for the macrostructure if the mould

face was studied. The specimens with larger porosity contain Virgin SAP and between the

two used dosages the one which was produced to achieve larger porosity has more

porosity. Also the distribution over the surface is important, and the test provides the

spacing factor which give shorter vales for the porous specimens.

Bio-receptivity

Regarding to the bio-receptivity of the specimens the colorimetric and the image

analysis measurements were studied. The colorimetric measurements show that the

specimen V2 was the pioneer specimen from the first weeks, these results correspond also

with visual inspection.

The colorimetric measurements of the first week reveal that the specimens’

surface has no equal colour therefore the reflectance curves were not coincident. After

some weeks (week 6) two mainly groups of specimens appear, the first group with higher

degree of colonization was composed by V1, C2 and V2. The second group with less

colonization was composed by the other specimens, C1, T1 and T2. By the end of the test,

the colorimetric measurements show that the reflectance curves for the specimen C2 and

V2 are equal. Comparing the results obtained with the fouling intensity V2 has higher

percentage of fouling intensity and also in the visual inspection more colonization was

seen. The specimen T1 has the second larger value for the fouling intensity close to the

value of V2.

According to the image analysis, the area of fouling was obtained. The specimen

with more area of the surface fouled is V2 followed by the specimen C2. With the visual

inspection it was shown that the fouling is slightly different thicker in V2, compared to C2,

which show has a thin growing over the surface. Specimens V1 and T1 have an equal

distribution of fouling on half of the surface.

Contrary to what was expected from the results of the absorption and desorption

test, the superabsorbent Virgin (V) has higher degree of bio-receptivity although more

absorption capacity was observed with TerraCottem (T). This is because, the porosity over

the surface is more abundant and well distributed for specimens with SAP Virgin than

with SAP TerraCottem, which show larger pores but less abundant. It should be noted that

this surface porosity is obtained without any treatment of the specimen and it is only due

to the effect of the SAP.

88 Chapter 6


From all the results especially from the colorimetric measurements and the image

analysis it can be concluded that the most suitable specimen to be colonized by Chlorella

vulgaris under laboratory conditions is V2.

From the analysis of the bio-receptivity under special conditions, the main

conclusion is that the process of colonization is going more slowly compared to the main

test, but with similar final results, as a result of the decrease of the growing during the dry

periods. By the end of the test, when the colonization is a little more introduced in the

specimen the dry periods do not affect much, and the growing continues during this dry

periods.

6.3. FURTHER PERSPECTIVES

Despite the contributions reported in the previous section, further research on the

topics covered in this document is required. For that reason, several suggestions for future

research are proposed below.

- Alternatively to the carbonation chamber used to achieve the suitable pH to

allow the colonization, study the reduction of the pH using additives.

- Despite the fact that the capacity of swelling of the SAP is important, it was

shown that not only the behaviour of the swelling of the SAP itself influence the

bio-receptivity but also is influenced mainly by the surface porosity that this

generates. For this reason, the other two initial SAPs studied would be

interesting to study the bio-receptivity under laboratory conditions.

- To have more results and to study more deeply the evolution under special

conditions of algae fouling test, one could perform the algae fouling test with

dry weeks over a longer period (e.g. 20 weeks).

References 89


REFERENCES

Anderson S.C. and Miller W.P. US Patent 7,438,95, 2008.

Andrade J.D. “Hydrogels for medical and related applications, ACS Symp. Series, 31,

American Chemical Society, Washington DC, 1, 1976.

Alum A., Mobasher B., Rashid A. and Abbaszadegan M. “Image analyses-based

nondisruptive method to quantify algal growth on concrete surfaces”. J Environ Eng, 135,

2009.

ASTM C642-06. Standard test method for density, absorption and void in hardened

concrete.

Bashaw R.N. and Harpe, B.G. United States Patent 3, 1966.

Buchholz F.L. and Graham A.T. (eds.). “Modern superabsorbent polymer technology”,

WILEY-VCH, New York, 1998.

Buchholz F.L. and Graham A.T. “Modern Superabsorbent Polymer Technology”, Wiley-

VCH, New York, Ch 1-7, 1998.

Buchholz F.L. and Peppas N.A. “Superabsorbent Polymers Science and Technology, ACS

Symposium Series”, 573, American Chemical society, Washington, DC, Ch 2, 7, 8, 9, 1994.

90 References


Collier N.C., Sharp J.H., Milestone N.B., Hill J. and Godfrey I.H. “The influence of water

removal techniques on the composition and microstructure of hardened cement pastes”.

Cem. Concr. Res. 38, 737–744, 2008.

De Muynck W., Maury Ramirez A., De Belie N. and Verstraete W. “Evaluation of

strategies to prevent algal fouling on white architectural and cellular concrete”.

International Biodeterioration & Biodegradation, 63, 2009.

Diamond S. “Mercury porosimetry — an inappropriate method for the measurement of pore

size distributions in cement-based materials”. Cem. Concr. Res. 30, (10), 1517–1525, 2000.

Elsen J., Lens N., Vyncke J., Aarre T., Quenard D. and Smolej V. “Quality assurance and

quality control of air entrained concrete”. Cem. Con. Res., 24 (7), pp. 1267–1276, 1994.

Escadeillas G., Bertron A., Ringot E., Blanc G. and Dubosc A. “Accelerated testing of

biological stain growth on external concrete walls. Part 2: Quantification of growths”. Mater

Struct, 42, 2009.

Favero-Longo S.E., Borghi A., Tretiach M. and Piervittori R. “In vitro receptivity of

carbonate rocks to endolithic lichen-forming aposymbionts”. Mycol Res, 113, 2009

Ferri L., Lottici P.P., Lorenzi A., Montenero A. and Salvioli-Mariani E. “Study of silica

nanoparticles — polysiloxane hydrophobic treatments for stone-based monument

protection”. J Cult Herit, 12(4), 63–356, 2011.

Golubic S., Friedmann I. and Schneider J. “The lithobiontic ecological niche, with special

reference to microorganisms”. J Sediment Petrol, 51, 1981.

Gorbushina A.A. “Life on the rocks”. Environ Microbiol, 9, 2007.

Guillitte O. “Bioreceptivity: a new concept for building ecology studies”. Sci Total Environ,

167, 1995.

Guillitte O. and Dreesen R. “Laboratory chamber studies and petrographical analysis as

bioreceptivity assessment tools of building materials”. Sci Total Environ, 1995.

Harmon C. United States Patent 3, 1972.

Harper B.G., Bashaw R.N. and Atkins B.L. French Patent 1, 1068.

Harper B.G., Bashaw R.N. and Atkins B.L. United States Patent 3, 1972.

Hueck H.J. “The biodeterioration of materials—an appraisal”. Int Biodeter Biodegr,48, 5-

11, 2001.

References 91


Jensen O.M. and Hansen P.F. “Water-entrained cement-based materials, PCT Patent

Application WO01/02317A1”. 2001

Jensen O.M. and Hansen P.F. “Water-entrained cement-based materials – II.

Implementation and experimental results”. Cement and Concrete Research, 32(6), 973–978,

2002.

Jensen O.M. “Use of superabsorbent polymers in construction materials”. In: Sun W et al.

(eds) Proceedings of the first international conference on Microstructure Related

Durability of Cementitious Composites, 13-15 October (Nanjing, China), 757–764, 2008.

Kabiri K. and Zohuriaan-Mehr M.J. “Superabsorbent hydrogels from concentrated solution

terpolymerization”. Iran Polym J, 13, 423-430, 2004.

Kabiri K., Faraji-Dana S. and Zohuriaan-Mehr M.J., “Novel sulfobetaine-sulfonic acid-

contained superswelling hydrogels”. Polym Adv Technol, 16, 659-666, 2005.

Kabiri K., Omidian H., Hashemi S.A. and Zohuriaan-Mehr M.J. “Concise synthesis of fast-

swelling superabsorbent hydrogels: Effect of initiator concentration on porosity and

absorption rate”. J Polym Mater, 20, 17-22, 2003.

Katchalsky A., Lifson S. and Eisenberg H. Journal of Polymer Science, 7, 1952.

Kern W. “Kunststoffe”, 28, 1938.

Kohler M. “Green facades – a view back and some visions”. Urb Ecosyst, 11, 423-426, 2008.

Konecny L. and Naqvi S.J. “The effect of different drying techniques on the pore size

distribution of blended cement mortars”. Cem. Concr. Res. 23, 1223–1228, 1993.

Korpa A. and Trettin R. “The influence of different drying methods on cement paste

microstructures as reflected by gas adsorption: comparison between freeze-drying (Fdrying),

D-drying, P-drying and oven-drying methods”. Cem. Concr. Res. 36, 634–649, 2006.

Krumbein W.E. “Microbial interactions with mineral materials”. In: Hougthon DR, Eggins S,

editors. Biodeterioration, 7. Elsevier Applied Science, 78-100, 1988.

Kuhn W., Hargitay B., Katchalsky A. and Eisenberg H. Nature, 165, 1950.

Li B., Liew O.W. and Anand A.K. “Use of reflectance spectroscopy for early detection of

calcium deficiency in plants”. In Proceeding of SPIE Vol. 5882, Third International

Conference on Experimental Mechanics and Third Conference of the Asian Committee on

Experimental Mechanics; Quan, C.; Chou, F.S.; Asundi, A.; Wong, B.S.; Lim, C.T., Ed.; SPIE,

Bellingham, WA; pp 693-697, 2005.

92 References


Liu K. and Baskaran B. “Thermal performance of green roofs through field evaluation”.

National Research Council Canada, 1-10, 2003.

Lura P., Jensen O.M. and Igarashi S-I. “Experimental observation of internal water curing

of concrete”. Mat Struct 40, 211–220, 2007.

Manso S., De Muynck W., Segura I., Aguado A., Steppe K., Boon N. and De Belie N.

“Bioreceptivity evaluation of cementitious materials designed to simulate biological growth”.

Science of the Total Environment 481, 232–241, 2014.

Manso S., Mestres G., Ginebra M.P., De Belie N., Segura I., and Aguado A. “Development

of a low pH cementitious material to enlarge bioreceptivity”. Construction and Building

Materials 54, 485–495, 2014.

Manso M. and Castro-Gomes J. “Green wall systems: A review of their characteristics”.

Renewable and Sustainable Energy Reviews, 41, 863-871, 2015.

Mechtcherine V., Reinhardt H.W., editors. “Application of superabsorbent polymers in

concrete construction. State-of-the-art report of the RILEM TC 225-SAP”. Springer, 2011.

Miller A., Dionísio A. and Macedo M.F. “Primary bioreceptivity: a comparative study of

different Portuguese lithotypes”. Int Biodeter Biodegr, 2006.

Miller A.Z., Dionísio A., Laiz L., Macedo M.F. and Saiz-Jimenez C. “The influence of

inherent properties of building limestones on their bioreceptivity to phototrophic

microorganisms”. Ann Microbiol, 59, 1–9, 2009a.

Miller A.Z., Laiz L., Dionísio A., Macedo M.F. and Saiz-Jimenez C. “Growth of

phototrophic biofilms from limestone monuments under laboratory conditions”. Int Biodeter

Biodegr, 2009b.

Miller A.Z., Leal N., Laiz L., Rogerio-Candelera M.A., Silva R.J.C., Dionisio A., et al.

“Primary bioreceptivity of limestones used in Southern Europe monuments”. In: Smith BJ,

Gomez- Heras M, Viles HA, Cassar J, editors. Limestone in the built environment: present

day challenges for the preservation of the past. Special Publications. London: Geological

Society, 79–92, 2010b.

Miller A.Z., Rogerio-Candelera M.A., Laiz L., Wierzchos J., Ascaso C. Sequeira Braga

M.A., et al. “Laboratory-induced endolithic growth in calcarenites: biodeteriorating

potential assessment”. Microb Ecol, 60, 55–68, 2010a.

Mindess S. and Young J.F. “Concrete”. Prentice-Hall, Englewood Cliffs, NJ, 1981.

Mindess S., Young J.F. and Darwin D. “Concrete”. Prentice Hall, 2nd Ed., 1996.

References 93


Mönnig S. “Superabsorbing additions in concrete – applications, modelling and comparison

of different internal water sources”. PhD Thesis, University of Stuttgart, 164, 2009.

Moriyoshi A., Fukai I. and Takeguchi M. “Nature”. 344, 230–232, 1990.

Moro F. and Bohni H. “Ink-bottle effect in mercury intrusion porosimetry of cement based

materials”. J. Colloid Interface Sci. 246, (1), 135–149, 2002.

Nukushina K. Yuki Gosei Kagaku, 38, 1980.

Obenski B. Nonwovens Industry, 25(11), 1994.

Orts W.J., Roa-Espinosa A., Sojka R.E., Glenn G.M., Imam S.H., Erlacher K. and

Pedersen J.S. J Mater Civil Eng 19:58, 235, 2007.

Papida S., Murphy W. and May E. “Enhancement of physical weathering of building stones

by microbial populations”. Int Biodeter Biodegr, 2000.

Po R. “Water-absorbent polymers: A patent survey”. J Macromol. Sci-Rev Macromol Chem

Phys, C34, 607-662, 1994.

Prieto B., Silva B. and Lantes O. “Biofilm quantification on stone surfaces: comparison of

various methods”. Sci Total Environ, 333, 1–7, 2004.

Prieto B. and Silva B. “Estimation of the potential bioreceptivity of granitic rocks from their

intrinsic properties”. Int Biodeter Biodegr, 2005.

Rafalko S.D., Filz G.M., Brandon T.L. and Mitchell J.K. Transport Res Rec 39 234, 2007.

Ramazani-Harandi M.J., Zohuriaan-Mehr M.J., Ershad-Langroudi A., Yousefi A.A.,

Kabiri K. “Rheological determination of the swollen gel strength of the superabsorbent

polymer hydrogels”, Polym Test, 25, 470-474, 2006.

Saiz-Jimenez C. “Biodeterioration of stone in historic buildings and monuments”. In:

Llewellyn GC, Dashek WW, O'Rear CE, editors. Mycotoxins, wood decay, plant stress,

biocorrosion, and general biodeterioration. Biodeterioration ResearchNew York: Plenum,

587–603, 1994.

Snoeck D., Steuperaert S., Van Tittelboom K., Dubruel P. and De Belie N. “Visualization

of water penetration in cementitious materials with superabsorbent polymers by means of

neutron radiography”. Cement and Concrete Research, 42, 1113–1121, 2012.

Snoeck D., Velasco L.F., Mignon A., Van Vlierberghe S., Dubruel P., Lodewyckx P. And

De Belie N. “The influence of different drying techniques on the water sorption properties of

cement-based materials”. Cement and Concrete Research 64, 54–62, 2014.

94 References


Snoeck D., Velasco L.F., Mignon A., Van Vlierberghe S., Dubruel P., Lodewyckx P. And

De Belie N. “The effects of superabsorbent polymers on the microstructure of cementitious

materials studied by means of sorption experiments”. Cement and Concrete Research 77,

26–35, 2015.

Tiano P., Accolla P. and Tomaselli L. “Phototrophic biodeteriogens on lithoid surfaces: an

ecological study”. Microb Ecol, 29, 299–309, 1995.

Tomaselli L., Lamenti G., Bosco M. and Tiano P. “Biodiversity of photosynthetic

microorganisms dwelling on stone monuments”. Int Biodeter Biodegr, 46, 2000.

Tran T.H., Govin A., Guyonnet R., Grosseau P., Lors C., Garcia-Diaz E., et al. “Influence

of the intrinsic characteristics of mortars on biofouling by Klebsormidium flaccidum”. Int

Biodeter Biodegr, 70, 2012.

Urzì C., De Leo F., Salamonee P. and Criseo G. “Airborne fungal spores colonising marbles

exposed in the terrace of Mesina Museum, Sicily”. Aerobiologia, 17, 2001.

Vogt P., Rohlen R. and Tennie M. WO/2004/016425 236, 2004.

Washburn E.W. “Note on a method of determining the distribution of pore sizes in a porous

material”. Porc. Natl. Acad. Sci. USA, 7, 115–116, 1921.

Winslow D.N. and Diamond S. “A mercury porosimetry study of evolution of porosity in

Portland cement”. J. Mater. 5, (3), 564–585, 1970.

Wong N.H. and Yu C. “Study of green areas and urban heat island in a tropical city”. Habitat

International 29, 547-558, 2005.

Zohuriaan-Mehr M.J. “Super-Absorbents”, Iran Polymer Society, Tehran, 2-4, 2008.

Zohuriaan-Mehr M.J. and Pourjavadi A. “Superabsorbent hydrogels from starch-g-PAN:

Effect of some reaction variables on swelling behavior”. J Polym Mater, 20, 113-120, 2003.

Zohuriaan-Mehr M.J., Motazedi Z., Kabiri K., Ershad-Langroudi A., Allahdadi I. “Gum

arabicacrylic superabsorbing hydrogel hybrids: Studies on swelling rate and environmental

responsiveness”, J Appl Polym Sci, 102, 5667-5674, 2006.

Zohuriaan-Mehr M.J., Omidian H., Doroudiani S. and Kabiri K. “Advances in non-

hygienic applications of superabsorbent hydrogel materials”. J Mater Sci 45, 5711-5735,

2010.

Zusatz B. and Nilsson F. WO/2004/101463 237, 2004.

http://www.edana.org

References 95


UIC, 2004 – University of Illinois at Chicago, 2004: The absorption spectrum of leaf

pigments. URL: http://www.uic.edu/classes/bios/bios100/lecturesf04am/absorption-

spectrum.jpg

96 References


Mortar production 97


APPENDIX A

Mortar production

1. INTRODUCTION

During the production of the mortars with SAPs it was shown that the total amount

of additional water should be defined during the mixture. Otherwise, if the additional

water was defined using the test results the desired consistency (similar to the

standardised mortar) was not achieved. For this reason the extra water was added slowly

making a consistency test between each step until reach the standardised mortar

consistency of approximately 16 cm. The values of the additional water and the figures

showing the consistency of each step are presented in this appendix.

2. CONSISTENCY TEST

2.1. SAP_1

Table A.1. Added water until the expected consistency for SAP_1

Code Extra

water [g] Consistency test


REF-SAP_1 - 159 160 159.5

SAP_1

40.0 120 123 121.5

60.0 135 136 135.5

70.0 148 150 149.0

75.0 159 160 159.5

98 Appendix A


a) 40ml of water before the blows b) 40ml of water after the blows

c) 60ml of water before the blows d) 60ml of water after the blows

e) 75ml of water before the blows f) 75ml of water after the blows

Figure A.1. Consistency test before and after the blows for SAP_1

2.2. SAP_2


Code Extra



REF-SAP_2 - 159 161 160.0

SAP_2

40.0 119 118 118.5

50.0 125 127 126.0

60.0 131 131 131.0

70.0 145 148 146.5

75.0 161 160 160.5

Mortar production 99




2.3. SAP_3


Code Extra



REF-SAP_3 - 159 160 159.5

SAP_3 40.0 151 150 150.5

50.0 159 160 159.5




100 Appendix A


2.4. SAP_4


Code Extra



REF-SAP_4 - 160 159 159.5

30.0 126 128 127.0

80.0 155 154 154.5

85.0 154 155 154.5

SAP_4 105.0 159 160 159.5



e) 105ml of water before the blows f) 105ml of water after the blows


Study of the effect of superabsorbent polymers on water...

Documents

Transcript of Study of the effect of superabsorbent polymers on water...