Polymer-based and bacteria-based self-healing concrete

Prof. Dr. Ir. Nele De Belie

DEPARTMENT OF STRUCTURAL ENGINEERINGMAGNEL LABORATORY FOR CONCRETE RESEARCH

OUTLINE

• Introduction

• Polymer based self-healing concrete

• Bacteria based self-healing concrete

• Conclusions

Bridges, locks, wharfs, piers, tunnels, …

CRACKING IN CONCRETE POSES SEVERAL PROBLEMS

CRACKING IN CONCRETE POSES SEVERAL PROBLEMS

Cl-

Cl-

Cl-

Cl-Cl-

Chloride resistance of uncracked concrete

If concrete cover is big enough, not much problems

Chlorides diffusing in concrete

concrete rebarexposure solution

Chloride resistance of cracked concrete

Cl-

Cl-Cl-

Cl-

Cl-

concrete rebarexposure solution

High risk for fast & localized corrosion initiation

CRACKING IN CONCRETE POSES SEVERAL PROBLEMS

External treatments are expensive and time consuming

Replacement of contaminated concrete

Epoxy to fill up the cracks Additional coating

AUTONOMOUS SELF-HEALING MAY HELP SOLVE DURABILITY PROBLEMS

Inspired by nature: - not designed to withstand everything- in case of failure: rapid detection

& ‘massive’ & efficient action

3 approaches at the Magnel lab:

(i) use of embedded bacterial spores cf. Wang (2013)(ii) use of superabsorbent polymers (SAPs) cf. Snoeck (2015)(iii) use of encapsulated polymers cf. Van Tittelboom (2012)

• Van Tittelboom, K., De Belie, N. (2013). Self-healing in cementitious materials – A review. Materials, 6(6), 2182-2217.

• Ferrara, L., Van Mullem, T., Alonso, M.C., Antonaci, P., Borg, R.P., Cuenca, E., Snoeck, D., Jefferson, A., Peled, A., Ng, P.I., Roig Flores, M., Serna Ros, P., Sanchez, M., Schroefl, C., Tulliani, J.M., De Belie, N. (2018). Experimental characterization of the self-healing capacity of cement based materials and its effects on the material performance: A state of the art report by COST Action SARCOS WG2. Construction and building materials, 167, 115-142.

• A. Jefferson, E. Javierre, B. Freeman, A. Zaoui, E. Koenders, L. Ferrara. Research Progress on Numerical Models for Self-Healing Cementitious Materials. Advanced Materials Interfaces (2018) 170378 (19 pages). DOI: 10.1002/admi.201701378.

• De Belie, N., Gruyaert, E., Al-tabbaa, A., Antonaci, P., Baera, C., Bajare, A., Darquennes, A., Davies, R., Ferrara, L., Jefferson, T., Litina, C., Miljevic, B., Otlewska, A., Ranogajec, J., Roig, M., Paine, K., Lukowski, P., Serna, P., Tulliani, J.-M., Vucetic, S., Wang, J., Jonkers, H.A. (2018). Review on self-healing concrete for damage management of structures. Special Issue “Self-healing materials”, Advanced Materials Interfaces. 1800074, 28 p.

REVIEWS

OUTLINE

• Introduction

• Polymer based self-healing concrete

• Bacteria based self-healing concrete

• Conclusions

Thin brass plate(thickness = 300 µm)

PVC mold

Nylon wire

Capsule filled with PU precursor

PhD Bjorn Van Belleghem, UGent, 2018

Chloride ingress in small samples with preplaced capsules

Department of Structural Engineering

Cracks cause increase in chloride concentration up to 18 times higher compared to uncracked concrete

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Department of Structural Engineering

Crack healing causes a reduction of chloride ingress through cracks up to 75%

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Department of Structural Engineering

Chloride profiling with EPMA

Uncracked

Cracked

Chloride ingress beyond the crack tipChloride ingress perpendicular to the crack face

Healed

• PMMA capsules by extrusion • Wall thickness controlled by conveyor speed• Øouter = 6.5 mm, w.t.= 0.7 mm, L = 50 mm• Healing agent: water repellent agent (WRA)• ~ 22 capsules per liter of concrete (3250 capsules)

(Adelaide Araujo, UGent)Chloride ingress in cracked concrete beams

• Beams of 2.5 m x 0.40 m x 0.20 m reinforced with four ribbed steel bars (Ø=10 mm)

• Cracks at 14 days formed by 3-point-bending• 6 cracks of variable width in each beam

Crack formation

• exposure to 3 wt% NaCl solution• flows over the beam for 24 h• once per week during 6 weeks

NaCl solution

Sides of beam waterproofed with

aluminum foil

Steel support

SH REF

Zones where WRA leaked out clearly visible

Durability testing: chloride ingress

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Macro-cell corrosion mechanism

Cl-

2Fe 2Fe2+ + 4e- 2H2O + O2 + 4e- 4OH-e-

H2O O2

2Fe2+ 4OH-

2Fe(OH)2

= anodic reaction = cathodic reactionMetal dissolution Oxygen reduction

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Reinforcement corrosion

Schematic test setup

Cl-

2Fe 2Fe2+ + 4e-

2H2O + O2 + 4e- 4OH-

H2O O2

2Fe2+ 4OH-

2Fe(OH)2

anodic reactioncathodic reaction

e- e-

Connection of anode and cathode outside the beam to have a closed circuit

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Macro-cell corrosion mechanism

Schematic test setup Steel reinforced concrete prisms 120 mm x 120 mm x 500 mm

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Crack creation by three point bending

Every specimen is mounted into a steel frame in order

to keep the cracks open

- Cracked at 28 days- 48 h at 20 °C and 60% RH

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Test setup

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NaClCa(OH)2Ca(OH)2

Specimens subjected to weekly wet-dry cycles1 day wet, 6 days dry

for total period of 44 weeks

Measurements

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Other electrochemical parameters were measured weekly with potentiostats

Specimens are all connected to a current logging system

Imacro measured every hour automatically

Imacro =E0,C − E0,A

RP,A + RP,C + Re

internal Ag/AgClreference electrode, or external saturated calomel reference electrode (SCE)

Monitoring macro-cell corrosion current

020406080

100120140160180

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I mac

ro(µ

A)

Week

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ro(µ

A)

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CR_EXT_A CR_EXT_B CR_EXT_C

Localized pitting corrosion on rebars of cracked samples

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Macro-cell corrosion current and potential

Service life prediction based on volume loss calculated by Faraday’s law

Volumetric mass loss of steel:3-6 mm³ 0.34-0.70 mm³/wk

Volumetric mass loss of steel:1-2 mm³ 0.03-0.05 mm³/wk

→ factor 14 lower

OUTLINE

• Introduction

• Polymer based self-healing concrete

• Bacteria based self-healing concrete

• Conclusions

Selection of micro-organisms

1. Ureolytic bacteria (ureum)2. Aerobic heterotrophic bacteria (e.g. lactate)3. Denitrifying bacteria (e.g. formate + nitrate)

Urea hydrolysisCO(NH2)2 + 2H2O + Ca(NO3)2 CaCO3 + 2NH4

+ + 2NO3-

Aerobic oxidationCa(CH3COO)2 + 4O2 CaCO3 + 3CO2 + 3H2O

Nitrate reductionCa(CH3COO)2 + 1.6Ca(NO3)2 2.6CaCO3 + 1.6N2 + 1.4CO2 + 3H2O

Self-healing bio-concrete: metabolic pathways

Axenic strains are delicate in harsh environments

They need protective carriers to survive the concrete environment +

They can avoid the need for protection if they collaborate

PhD Yusuf C. Ersan, UGent

Oosterweel: solving the traffic problems in Antwerp1st application of self-healing concrete in Belgium

Mixed UreolyticCulture (MUC)

Non-axenic culture, obtained by upgrading a side stream from the vegetable industry

before grinding after grinding PhD Filipe Silva, UGent

1st application of self-healing concrete in Belgium

1st application of self-healing concrete in Belgium

Mix design• CEM III/B

• 1m% vs cement weight of MUC+, added dry

• nutrients: urea and calcium nitrate tetrahydrate: dissolved in 40 l water

• agents were added via inspection hatchBUT took a long time high air content 4.7%

Age fcm

7 days 30.7 MPa 28 days 45.0 MPa 93 days 54.7 MPa

Compressive strength

Construction site: concrete casting

• E-mod specimens

• Tensile specimens with 1 bar Ø 16 mm(100x100x400 mm³)

• Capillary water absorption specimens(120x120x500 mm³)

• Water flow specimens (150x150x550 mm³)

Testing in the lab

Water flow setup to test water permeabilityBased on the test method designed in HEALCON

To monitor the water outflow from the (healed) crack in function of time (5 - 15 min)

Water-saturatedprism

• Cracked after 6 weeks in manual 3P bending

• until residual CW of 320 – 385 µm

• Sealing of the crack at the side surfaces

• Saturation for 5 days

• Initial water flow (1 bar)

• Repetitive cycle of 3 weeks healing and testing

Ø 10 mm

Ø 6 mm

6 cm

3 cm

Water flow setup to test water permeability

335 µm320 µm352 µm383 µm352 µm0

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WF [g/min]

Initial water flow

SE =𝑊𝑊𝐹𝐹𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖 − 𝑊𝑊𝐹𝐹𝑖𝑖

𝑊𝑊𝐹𝐹𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖𝑖� 100%

Sealing efficiency results

0%

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Evolution of SE

1 (335 µm)2 (320 µm)3 (352 µm)4 (383 µm)5 (352 µm)

Up to date, no cracks have been noticed

Installation of roof plate

anoxic (denitrifiers)aerobic

• Sequencing batch reactor• Selective pressure (alkaline pH,

starvation, wash out)

Activated Compact Denitrifying Core (ACDC)Non-axenic cultures of NO3

- reducing bacteria encapsulated in bio-polymer and co-cultures.

• Granulation & drying at 60°C• 0.5 – 2 mm granules• 70 % bacteria, 30 % Ca-salts• Added to mortar: 0.5-1 wt-% vs cement

85 mg/L N reduced in 2 days

At pH 9.8 after 28 days in mortar

ACDC could revive between 3 to 7 days.

Survival in mortar0.5 % ACDC, 2 % Ca-formate, 3 % Ca-nitrate vs cement

43

ERŞAN, Y.C., VAN TITTELBOOM, K., BOON, N., DE BELIE, N. (2018). Nitrite producing bacteria inhibit reinforcement bar corrosion in cementitious materials. Nature -Scientific Reports, 8: 14092.

a) plain mortar: standard sand (1350 g), CEM I 52.5 N cement (450 g) and tap water (225 g) (EN 196–1)

b) microbial test mortar with ACDC (0.5% wt/wt cement), Ca(NO3)2 (3%) and Ca(HCOO)2 (2%)

c) positive control: NO2– (1.6%) as a corrosion inhibitor in the

form of NaNO2 and Ca(HCOO)2 (2% wt/wt cement)d) abiotic control: nutrients, Ca(NO3)2 (3%) and Ca(HCOO)2 (2%) e) microbial self-healing control: CERUP (ureolytic) (0.5%) and

CO(NH2)2 (5%)

Materials

Corrosion inhibition test in concrete

• mortar specimens (40 mm × 40 mm × 160 mm) with a centrally positioned embedded smooth steel rebar (Ø=8 mm)

• artificial cracks with a depth of 20 mm and a width of ~300 µm created after 1 d

• cured for 28 d, 20°C, RH >90%

Methods

VAN TITTELBOOM, K., VAN BELLEGHEM, B., BOONE, M., VAN HOOREBEKE, L., DE BELIE, N. (2017). Use of X-ray radiography to […] judge the delay in corrosion through self-repair by encapsulated polyurethane. Advanced materials interfaces, 1701021, 10 p.

D

• six cracked and six uncracked pieces (38 mm × 40 mm × 15 mm) were sawn off

• cracked surface immersed in 0.5 M Cl– solution for 28 or 120 d

Results: healingplain mortar

positive control:NaNO2

abiotic control: NO3

–

microbial self-healing control: CERUP

microbial test mortar with ACDC

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Results: OCP (open circuit potential) monitored vs a saturated calomel electrode (SCE) for 120 days, data converted to standard hydrogen electrode (SHE)

16 d

Plain mortar and positive control with NaNO2

Microbial produced NO2- inhibits corrosion

44 d 28 d

18 d

Ca(NO3)2

NaNO2 ACDC

CERUP

Gravimetric mass loss of rebars due to corrosion

Conclusions

• Even small cracks may impair durability / self-healing improves durability• Durability of self-healing concrete has only scarcely been studied; mostly

indirect indicators such as water absorption / permeability are measured• Encapsulated low viscosity PU: mostly complete and consistent crack healing

o Reduction of chloride ingress up to 75% possibleo Significantly reduced corrosion propagation

• 1st application of self-healing concrete with MUC+ in Antwerp was successful; no cracks have been formed until now

• Bacterial ACDC granules provide concurrent corrosion inhibition & healing• Healing of 300 µm wide cracks was complete in less than 1 month time • During exposure to chloride solution, reinforcement protection was

comparable with that of cracked mortar containing chemical inhibitor or even uncracked mortar, due to the nitrite release by the denitrifying granules

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AcknowledgementsWith special thanks to:

PhD students and postdocs

FWO, IWT, SIM-Flanders, BOF-UGent, EC for financial support