Post on 06-Jan-2022
Use of Nanotechnology in Concrete
by
Lochana Poudyal, B.E.
A Thesis
In
Civil Engineering
Submitted to the Graduate Faculty
of Texas Tech University in
Partial Fulfillment of
the Requirements for
the Degree of
MASTER OF SCIENCES
Approved
Moon Won, Ph.D., P.E.
Chair of Committee
Priyantha W. Jayawickrama, Ph.D.
Mark Sheridan, Ph.D.
Dean of the Graduate School
May, 2018
Copyright 2018, Lochana Poudyal
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ACKNOWLEDGMENTS
I express my gratitude to my advisor and committee chair, Dr. Moon Won for his support
and guidance on this thesis and throughout my graduate studies at Texas Tech University.
I thank Dr. Priyantha W. Jayawickrama for his help and guidance on this research project
and throughout my graduate studies.
I also thank my family, friends and colleagues who supported me in numerous ways.
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TABLE OF CONTENTS
ACKNOWLEDGMENTS .................................................................................................. ii
ABSTRACT ...................................................................................................................... vii
LIST OF FIGURES ......................................................................................................... viii
LIST OF TABLES .............................................................................................................. x
LIST OF ABBREVIATIONS ........................................................................................... xii
I. INTRODUCTION ........................................................................................................... 1
Objective of research ....................................................................................................... 4
Research Context............................................................................................................. 5
Production of ordinary Portland cement ......................................................................... 6
Grinding and blending ..................................................................................................6
Burning – cement clinker formation .............................................................................7
Formation of cement .....................................................................................................9
Type I ......................................................................................................................11
Type II ......................................................................................................................12
Type III ......................................................................................................................12
Type IV ......................................................................................................................12
Type V ......................................................................................................................13
White cement ..............................................................................................................13
Hydrophobic cement ...................................................................................................13
Blended cement ..........................................................................................................13
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Air-entraining cement .................................................................................................13
High alumina cement ..................................................................................................14
Overview of thesis ......................................................................................................... 15
II. LITERATURE REVIEW ............................................................................................. 17
Supplementary cementitious materials (SCMs) ............................................................ 17
Fly Ash ......................................................................................................................18
GGBFS ......................................................................................................................24
Rice Husk Ash (RHA) ................................................................................................27
Pumice ......................................................................................................................28
Silica Fume .................................................................................................................29
Metakaolin ..................................................................................................................30
Sewage sludge ash ......................................................................................................32
Nano Concrete ............................................................................................................... 33
Nano Calcium carbonate ............................................................................................... 34
III. MATERIALS .............................................................................................................. 37
Coarse Aggregate .......................................................................................................... 37
Fine Aggregate .............................................................................................................. 37
Fly Ash .......................................................................................................................... 38
Ordinary Portland cement ............................................................................................. 38
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Nano Calcium Carbonate .............................................................................................. 39
IV. METHODS ................................................................................................................. 40
Properties of coarse aggregate....................................................................................... 40
Absorption and specific gravity of coarse aggregate ..................................................40
Absorption and specific gravity of fine aggregate ......................................................41
Moisture content for coarse and fine aggregate ..........................................................42
Sieve analysis for coarse and fine aggregate ..............................................................42
Tests conducted on fresh concrete ................................................................................ 42
Workability .................................................................................................................43
Setting time .................................................................................................................43
Heat of hydration ........................................................................................................44
Tests conducted on hardened concrete .......................................................................... 44
Compressive strength .................................................................................................44
Modulus of elasticity ..................................................................................................45
Shrinkage Ring test .....................................................................................................45
Design matrix ................................................................................................................ 46
V. RESULTS .................................................................................................................... 48
Workability.................................................................................................................... 48
Setting test ..................................................................................................................... 49
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Heat of hydration ........................................................................................................... 52
Compressive strength .................................................................................................... 54
Elastic modulus ............................................................................................................. 57
Shrinkage Ring Test ...................................................................................................... 60
VI. DISCUSSIONS........................................................................................................... 62
VII. SUMMARY & RECOMMENDATIONS................................................................. 64
REFERENCES ................................................................................................................. 66
APPENDIX ....................................................................................................................... 68
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ABSTRACT
Nanoparticles infused concrete also known as nano concrete has been an
unindustrialized area of research that is yet to be commercialized. These exorbitant
materials are still in progress of having their prices reduced through different sustainable
production to get their way into the concrete industry as sustainable, durable and
economical material. In contrast, nano CaCO3, a widely used material in pharmaceutical
and different other industry, is one of the cheapest nanomaterials that could be used in
construction industry. This study consists of preliminary analysis to understand the
behavior of concrete infused with nano CaCO3. Ordinary concrete and fly ash concrete was
mixed with 1% and 3% nano calcium carbonate. Workability, setting time and calorimeter
test were conducted to understand the change in the behavior of fresh concrete. Similarly,
compressive strength, elastic modulus and shrinkage ring test were conducted on hardened
concrete. Results indicated an enormous increase in the rate of hydration and early strength
after addition of nano CaCO3. However, a decrease in heat of hydration and elastic modulus
was observed with the addition of nano calcium carbonate. This unique property makes
nano concrete more crack resistant which was observed through shrinkage ring test.
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LIST OF FIGURES
1.1 The relative size of materials used in the construction industry (SOBOLEV, 2016).
................................................................................................................................... 1
1.2 Strength assessment of concrete with nano SiO2 (Hanus, 2008). ............................. 3
1.3 Rate of hydration of different compounds in concrete (won). ................................ 11
2.1 Left to Right: Class C fly ash, Metakaolin, Silica fume, Class F fly ash, Slag,
Calcined shale. (THE CONCRETE COUNTERTOP INSTITUTE, n.d.). .............. 17
2.2 Typical class C Fly ash (Alibaba, n.d.). ................................................................... 18
2.3 Morphology of Fly ash (Won, 2016)........................................................................ 20
2.4 Typical GGBFS used in construction industry (Alibaba, n.d.). ............................... 25
2.5 Morphology of GGBFS under SEM (Janardhanan, 2015). ..................................... 26
2.6 Several stages of Rice Husk Ash (Thomas, 2018). .................................................. 27
2.7 Typical volcanic ash (Geology, n.d.). ...................................................................... 28
2.8 Morphology of Silica Fume under SEM (Pittsburgh Mineral and Environmental
Technology, Inc, n.d.). ............................................................................................. 30
2.9 Morphology of Metakaolin under SEM (Hindawi, n.d.). ........................................ 31
2.10 Schematic figure to produce nano calcium carbonate (Eda Ulkeryildiz, 2016). ..... 35
2.11 Varied sizes of nano calcium carbonate (Gupta, 2004). .......................................... 36
5.1 Slump for different samples. .................................................................................... 49
5.2 Penetration resistance for ordinary concrete, and 1% and 3% nano
replacement in ordinary concrete ............................................................................ 50
5.3 Penetration resistance for F35, and 1% and 3% replacement
of nano in F35 .......................................................................................................... 51
5.4 Penetration resistance for F45, and 1% and 3% replacement
of nano in F45 .......................................................................................................... 51
5.5 Setting time for all samples...................................................................................... 52
5.6 Heat of hydration for samples 0 – 0, 3 – 0, 3 - 35 ................................................... 53
5.7 Heat of hydration for samples 0 – 0, 1 – 0, 1 - 45 ................................................... 54
5.8 Compressive strength for samples 0 – 0, 1 – 0, 3 - 0 ............................................... 55
5.9 Compressive strength for samples 0 – 35, 1 – 35, 3 – 35 ........................................ 56
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5.10 Compressive strength for samples 0 – 45, 1 – 45, 3 - 45 ......................................... 56
5.11 Compressive strength for all samples ...................................................................... 57
5.12 Elastic modulus for samples 0 – 0, 1 – 0, 3 - 0 ........................................................ 58
5.13 Elastic modulus for samples 0 – 35, 1 – 35, 3 - 35 .................................................. 59
5.14 Elastic modulus for samples 0 – 45, 1 – 45, 3 - 45 .................................................. 59
5.15 Elastic modulus for all samples ............................................................................... 60
A 1 Gradation of coarse aggregates used. ...................................................................... 68
A 2 Gradation of fine aggregates. .................................................................................. 69
A 3 Slump test conducted for fresh concrete. ................................................................ 79
A 4 Preparation of sample for setting time. ................................................................... 79
A 5 Compressive strength Testing machine. ................................................................. 80
A 6 Concrete mold after removal of outer ring for shrinkage ring test. ........................ 80
A 7 Data logger used for shrinkage ring test. ................................................................ 81
A 8 Compaction of sample in the plastic mold for compressive strength
and elastic modulus. ................................................................................................ 81
A 9 Elastic modulus Test. .............................................................................................. 82
A 10 Semi-adiabatic calorimeter used for determining heat of hydration on
fresh concrete. ..................................... ................................................................... 82
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LIST OF TABLES
1.1 Mineral composition of ordinary Portland cement ................................................... 6
1.2 Typical output from the kiln ..................................................................................... 9
1.3 Categories of several types of cement .................................................................... 11
2.1 Materials price sourced from Alibaba and eBay website ........................................ 34
3.1 Properties of Coarse Aggregate ............................................................................... 37
3.2 Properties of fine aggregate ..................................................................................... 38
3.3 Composition of Fly ash ............................................................................................ 38
3.4 Composition of nano CaCO3 ................................................................................... 39
4.1 Design matrix ........................................................................................................... 40
4.2 Different notation used to differentiate samples. ..................................................... 47
A 1 Sieve Analysis of coarse aggregates ........................................................................ 68
A 2 Sieve Analysis of fine aggregates ............................................................................ 69
A 3 Mix design for all the samples ................................................................................. 70
A 4 Setting time data for sample 0-0 .............................................................................. 70
A 5 Setting time data for sample 1-0 .............................................................................. 71
A 6 Setting time data for sample 3-0 .............................................................................. 71
A 7 Setting time data for sample 0-35 ............................................................................ 71
A 8 Setting time data for sample 1-35 ............................................................................ 72
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A 9 Setting time data for sample 3-35 ............................................................................ 72
A 10 Setting time data for sample 0-45 ............................................................................ 73
A 11 Setting time data for sample 1-45 ............................................................................ 73
A 12 Setting time data for sample 3-45 ............................................................................ 74
A 13 Compressive strength for all samples for 1 day ....................................................... 74
A 14 Compressive strength for all samples for 3 days ..................................................... 75
A 15 Compressive strength for all samples for 7 days ..................................................... 75
A 16 Compressive strength for all samples for 28 days ................................................... 76
A 17 Elastic modulus frequency for all samples for 1 day ............................................... 76
A 18 Elastic modulus frequency for all samples for 3 days ............................................. 77
A 19 Elastic modulus frequency for all samples for 7 days ............................................. 77
A 20 Elastic modulus frequency for all samples for 28 days ........................................... 78
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LIST OF ABBREVIATIONS
F35 – Concrete with 35% Fly ash by mass of cement
F45 – Concrete with 45% Fly ash by mass of cement
SCMs – Supplementary Cementitious Materials
HVFA – High Volume Fly ash
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CHAPTER I
INTRODUCTION
Nanoparticles have been widely used in different fields including but not limited to
medical industry, pharmaceutical, and construction. Use of nanoparticles in concrete is one
of the few emerging topics. Nano TiO2, nano SiO2, nano Al2O3, nano Fe3O4, nano ZrO2,
carbon nanotubes and carbon nanofibers are most commonly used nanoparticles in the field
of research (Hanus, 2008). These particles have shown a phenomenal effect in the
hydration of concrete through a nucleation process. They act as a seed for the hydration of
calcium silicate hydrate. Higher the rate of hydration, earlier is the strength gain in
concrete. Same materials behave differently with the decrease in the size of particles. For
instance, rice husk ash and nano SiO2 are same siliceous material. However, the behavior
of these materials in concrete is very different. Figure 1.1 provides us an idea about the
distribution of different material size used in construction industry.
Figure 1.1 The relative size of materials used in the construction industry (SOBOLEV, 2016)
Incorporating nanoparticle in concrete offers many advantages including ultra-high
compressive strength, high split tensile strength and ductility, high aggregate paste
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bonding, and higher thermal durability – thus can be used in refractory concrete
(SOBOLEV, 2016). It also offers anti-microbial surfaces, which would be ideal for
hospitals, health care center and nursing center (Hanus, 2008). These materials also
increase the durability of high traffic rigid pavement, as it offers higher resistance to
thermal shock and abrasion. Moreover, nano TiO2 has also been used for coating of steel
reinforcement as it offers better corrosion resistance (Hanus, 2008). Thus, the use of
nanoparticles in concrete has enhanced the efficiency and performance of ordinary
concrete.
Industrial waste products such as Fly Ash, GGBFS, sludge sewages are widely used
as they make concrete more sustainable, workable, finish able, and mainly increases the
later age strength. In contrast, it reduces the early strength of concrete significantly. The
dosage of these supplementary cementitious material (SCMs) has been limited due to a
decrease in early strength. However, the addition of nano SiO2 to SCM modified concrete
has helped in improving the early compressive strength, split tensile strength, flexural
strength, permeability, abrasion resistance, due to increase in the rate of pozzolanic reaction
(Hanus, 2008). Nano SiO2 is produced from agricultural waste Rice Husk Ash (RHA) and
helps in improving the durability, sustainability, and performance of concrete (Ehsani,
2016). Figure 1.2 shows the increase in early strength of concrete with the addition of nano
SiO2.
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Figure 1.2 Strength assessment of concrete with nano SiO2 (Hanus, 2008).
Moreover, the addition of carbon nanotubes (CNTs) and carbon nanofibers (CNFs)
also compensates the loss of early strength due to the addition of Fly Ash, mainly the tensile
strength. The tensile strength and Young's modulus of CNTs are 100 times higher than the
steel, however weight per volume ratio is extremely lower than the steel (Hanus, 2008).
Thus, these properties could help in producing concrete with higher tensile strength without
the use of steel reinforcement.
However, as much as these nanoparticles have an excellent effect on the properties
of concrete, they are not used as much commercially, due to rare availability and the high
price of these materials. In fact, CNTs and CNFs are not even manufactured commercially
in large scale (Hanus, 2008). Researchers are trying to improve the manufacturing
technology to produce nanoparticles in large scale so that they would be readily available
at reasonable price.
Nano CaCO3, on the other hand, is used in the various technical field such as medical
industry, and pharmaceuticals. Due to its wide application, nano CaCO3 is relatively
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produced in a rather large scale as compared to other nano-materials. In addition, it is
cheaper than the ordinary Portland cement. This report describes the experiments
conducted to evaluate the modifications to concrete properties affected by the inclusion of
nano CaCO3.
Objective of research
There has been various work done to improve the properties of concrete, especially to
make it more sustainable and efficient at the same time. As concrete is one of the main
sources to release CO2 in the air, any efforts to reduce the amount of cement needed to
produce concrete without compromising concrete properties would be beneficial. Use of
industrial and agricultural waste such as Fly Ash, GGBFS, sewage sludge, RHA etc. has
helped in a certain amount to meet the criteria of sustainable and durable concrete,
however, the use of those materials also reduces the early strength of concrete due to slow
hydration. Modern technology such as incorporating nanoparticles in concrete, which are
thousands of times smaller than cement, could help in increase in the rate of hydration and
filling the nanopores, making concrete more durable and crack resistant. Some
nanoparticles have also shown to increase the tensile strength of concrete without the use
of steel reinforcement. Thus, there has been an increased interest in using these
nanoparticles to make high efficient and smart concrete. If more research is conducted in
this area, concrete with higher sustainability, durability and higher performance could be
achieved for a new generation. The objective of this research was to investigate the
modifications to concrete properties, especially early age strength, of concrete containing
fly ash if certain amount of cement is replaced with nano CaCO3. In this report, use of nano
CaCO3 in concrete has been tested in both fresh and hardened concrete. Material properties
evaluated for fresh concrete are:
✓ Workability
✓ Setting time
Those evaluated for hardened concrete are:
✓ Compressive strength
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✓ Modulus of elasticity
✓ Permeability
✓ Cracking potential
Thus, this thesis includes a detailed analysis of change in fresh and hardened concrete
properties after the addition of nano CaCO3.
Research Context
To fully understand the research problem, one must have a fair knowledge of the
production of concrete, its compositions, applications, and limitations that have been faced
in the construction industry till date.
Concrete is a composite material that consists of cement, coarse aggregates, fine
aggregates, water, and admixture. Concrete is one of the main building materials used in
construction industry. Concrete is very high in compression, but very low in tension, thus
reinforcements are used to compensate the tensile strength, making it a suitable building
material for every construction. Despite its wide applicability, it is also one of the main
materials that produce high greenhouse gases during production; 8% of the total CO2
emission is from cement production.
Ordinary Portland cement consists of four main oxides: Calcium oxide (CaO),
Silicon dioxide (SiO2), Sulphur trioxide (SO3) aluminum trioxide (Al2O3), and ferric oxide
(Fe2O3). Similarly, the mineral composition of different solids present in the cement is
summarized in the Table 1.1.
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Table 1.1 Mineral composition of ordinary Portland cement.
Mineral
name
Cement
notation
Oxide formula Chemical
formula
Chemical name
Alite C3S 3CaO.SiO2 Ca3SiO5 Tricalcium
Silicate
Belite C2S 2CaO.SiO2 Ca2SiO4 Dicalcium
Silicate
Aluminate C3A 3CaO.Al2O3 Ca3Al2O6 Tricalcium
Aluminate
Ferrite C4AF 4CaO.Al2O3.Fe2O3 Ca2AlFeO5 Tetracalcium
Aluminoferrite
Portlandite CH CaO.H2O Ca(OH)2 Calcium
hydroxide
Gypsum CSH2 CaO.SO3.2H2O CaSO4.2H2O Calcium sulfate
dihydrate
Lime C CaO CaO Calcium oxide
Production of ordinary Portland cement
Ordinary Portland cement is manufactured in the cement plant. Limestone, sand,
clay, and iron ores are the common raw materials needed, which are then ground and burnt
to make cement clinkers. Finally, the cement clinkers are finely grounded in the kiln at
elevated temperature to produce cement. The step by step process for the manufacture of
cement is discussed in detailed below (The science of concrete, n.d.).
Grinding and blending
Prior to sending the raw materials into the kiln, they are ground and blended
together using either dry process or wet process (The science of concrete, n.d.). The water
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facilitates the grinding process but then the water needs to be removed before the materials
are entered the kiln, thus consumes more energy and time. The wet process is now almost
obsolete as most of the manufacturing plant uses a high efficient grinding machine that
facilitates dry grinding (The science of concrete, n.d.).
Burning – cement clinker formation
The blended materials are then burnt down in a different process to form cement
clinkers. Variety of fuels such as coal, natural gas, fuel oil, lignite etc. are used to burn the
kiln at the bottom (The science of concrete, n.d.). This process requires the maximum
temperature and energy. The raw materials are brought at the upper end of the kiln and are
entered where the materials move to the bottom and are slowly rotated and moved forward
such that enough time is allowed for each reaction to be completed at appropriate
temperatures (The science of concrete, n.d.). In this process, there are different reaction
zones that are again furthered discussed in detail below.
Dehydration zone (up to 450oC)
The blended raw mixtures are dehydrated in this zone to make the materials
completely free from moisture. This process is mandatory even the grinding is done
through the dry process to remove adsorbed moisture.
Calcination zone (450oC – 900oC)
In this zone, the dehydrated mix is burnt at a higher temperature to make oxides out
of solid materials (The science of concrete, n.d.). At the end of this zone, the kiln consists
of all four oxides Calcium oxide (CaO), Silicon dioxide (SiO2), Sulphur trioxide (SO3)
aluminum trioxide (Al2O3), and ferric oxide (Fe2O3), which are then ready to undergo
further reaction (The science of concrete, n.d.). Calcination refers to decomposing of solid
material.
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Solid state reaction zone (900oC – 1300oC)
In this zone, the reaction starts in the solid state to form Dicalcium silicate (C2S),
one of the main mineral ingredients in cement (The science of concrete, n.d.). The reactive
silica and calcium oxide combine to form blite (C2S). Also, calcium aluminates (C3A) and
calcium ferrites (C4AF) are formed in this zone which is later used in a clinkering zone to
reduce the temperature for the formation of tricalcium silicate (C3S). The calcium
aluminates and ferrites melt at a lower temperature (~1300oC) and help in a faster rate of
reaction in the clinkering zone to reduce the temperature. Following different reactions
undergo at this stage to form different minerals.
2CaO + SiO2 CaO.SiO2 (C2S)
3CaO + SiO2 3CaO.SiO2 (C3S)
3CaO + Al2O3 CaO.Al2O3 (C2A)
4CaO + Al2O3 + Fe2O3 4CaO.Al2O3.Fe2O3 (C4AF)
Clinkering zone (1300oC – 1500oC)
This is the hottest zone where tricalcium silicates (C3S) are formed, one of the main
components responsible for the strength of the concrete. At first, C3A and C4AF melt which
causes to mix to agglomerate into big nodules bound by a thin layer of liquid (The science
of concrete, n.d.). Inside this liquid, C2S crystals react with CaO to form C3S. Thus, the
crystals of C3S grow inside the liquid while the number of C2S decreases (The science of
concrete, n.d.). This zone is completed when all the amount of silica is converted into C3S
and C2S and amount of CaO is reduced to <1% (The science of concrete, n.d.). Finally,
cement clinkers are formed which consists of all cement minerals but in the solid state.
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Cooling zone
The clinkers are cooled rapidly either by blow drying or using water to avoid the
decomposition of C3S back into C2S and CaO and to have a more reactive cement.
Formation of cement
In this process, the cement clinkers are now ground into a fine powder to form
Portland cement. Gypsum (CSH2) is added in this process to avoid the flash set of cement
due to the presence calcium aluminates and ferrites (The science of concrete, n.d.). At this
stage, the manufacture of cement is complete and is ready to be bagged and transported.
The typical kiln output consists of following main mineral components:
Table 1.2 Typical output from the kiln.
Cement
compound
Output
C3S 49%
C2S 25%
C3A 12%
C4AF 8%
Each of the cement minerals has their own contribution to make the cement better
and efficient. Some contribute at the production plant, while some contribute during the
hydration of cement. The properties of different mineral present in cement are discussed in
the section below.
Tricalcium silicate (C3S)
They are one of the main components that contribute to the strength of cement paste
due to the formation of calcium silicate hydrate. C3S, also known as alite, comprises half
of the cement composition. Reactions involved in hydration of C3S is shown below.
2C3S + 6H 3CaO.2SiO2.3H2O + 3CH
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Dicalcium silicate (C2S)
They comprise about a quarter of the cement composition and is not as reactive as
alite. But, C2S contributes to the later age strength of cement paste. Hydration of C2S is
explained below with reactions.
2C2S + 4H 3CaO.2SiO2.3H2O + CH
Tricalcium aluminates (C3A)
This mineral comprises roughly 12% of cement composite and is the fastest
reacting mineral which causes a flash set of the cement paste. Thus, gypsum is added to
delay the hydration of C3A. These minerals contribute little to no strength gain of the
cement paste. However, they contribute to reducing the temperature by (~1000oC) of a
cement kiln in a production plant in the clinkering zone, in the formation of the elite.
Hydration of tricalcium aluminates is explained by following reactions.
C3A + 3CSH2 + 26H C6AS3H32 (ettringite)
C6AS3H32 + 2C3A + 22H 3C4ASH18 (Monosulfate)
Tetracalcium aluminoferrite (C4AF)
This compound also has the same contribution as that of tricalcium aluminates and
do not contribute to the strength of cement paste. They are used as fluxing agents to reduce
the temperature in a concrete plant in the clinkering zone. Hydration of tetracalcium
aluminoferrite is explained by following reactions.
C4AF + 3CSH2 + 26H C6AS3H32 (ettringite)
C6AS3H32 + 2C3A + 22H 3C4ASH18 (Monosulfate)
Figure 1.3 shows the contribution of different cement compounds to the strength of
concrete at different ages.
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Figure 1.3 Rate of hydration of different compounds in concrete (Won, 2016).
Depending on the percentage composition of different cement compounds, the
cement produced in concrete plant differs. These are used for different application
purposes. ASTM has classified cement into five various categories depending on the C3S
and C3A content. Different types of cement according to ASTM is given in Table 1.3.
Table 1.3 Categories of several types of cement.
Cement Types C3A content C3S content
Type I - Fairly high
Type II <8% Fairly high
Type III - High
Type IV Low Low
Type V <5% Fairly high
Type I
They are ordinary Portland cement used for the general purpose: buildings, precast
unit, pavements etc. C3S content is fairly high to increase the early strength.
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Type II
It has low C3A content for moderate sulfate resistant concrete. Type I/II cement is
also available that meets the requirement for both type of cement, i.e., it has fairly high
early strength and is also sulfate resistant. Sulfate attack is a genuine issue in concrete.
Sulfate ions react with C3A to form ettringite and increase the volume of concrete causing
it to expand and crack.
Na2SO4 + Ca(OH)2 + 2H2O CaSO42H2O + 2NaOH
MgSO4 + Ca(OH)2 + 2H2O CaSO42H2O + Mg(OH)2
C3A + 3CaSO42H2O + 26H C6AS3H32 (ettringite)
Type III
This type of cement is used for an application that needs high early strength. C3S is
ground more finely and is high in amount compared to other types of cement, to increase
the rate of hydration. It is used mainly for quick repairs of infrastructure, rapid pace of
construction to bear loads sooner, and in precast plants to remove the form quicker.
However, short workability, the greater heat of hydration and lower ultimate strength limits
the use of this type of cement.
Type IV
This type of cement is also known as slow reacting cement, as the amount of C3S
is reduced significantly. This type of cement was produced after problems related to the
high heat of hydration was an issue when Type III cement was used. This type of cement
is used in big structures like dams and bridges to reduce the core temperature of concrete,
thus decreasing the early age cracking and increasing ultimate strength of concrete. Low
C3A content is also another advantage for sulfate prone places.
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Type V
Construction places prone to high sulfate attack uses this type of cement, as it has
the lowest amount of C3A content (<5%). The early age strength is like that of Type I or
Type I/II cement.
Other types of cement produced that are customized for different application are:
White cement
This is used for decoration purposes to give artistic look to the infrastructure. The
white color is attained by reducing the iron and magnesium content that gives cement grey
color. The strength and other properties are like that of Type I cement.
Hydrophobic cement
Water infrastructures like dams and bridges use this type of cement, where the
cement surface is hydrophobic, i.e., it repels water making it water resistant concrete. It is
also used in places where monsoon season is dominant, and cement cannot be stored for
longer time.
Blended cement
Cement is replaced (~65% by wt.) during the grinding of cement clinker with
GGBFS to produce blended cement. This has similar properties to that of Type III cement,
thus Type III cement is produced rarely. This is also the sustainable type of cement as it is
utilizing industrial waste produce cement.
Air-entraining cement
Air entraining agent is used in places that face the problem of freeze and thaw
periodically. Entrained air helps to escape the water present inside the concrete during
freezing weather to reduce the expansion of concrete. Similarly, the water is released back
to concrete during hot weather. This type of cement is produced using air entraining agent
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such as resins, glues, sodium salts of sulfate with Ordinary Portland cement (The science
of concrete, n.d.).
High alumina cement
Very high compressive strength is the special feature of this type of cement. Bauxite
(aluminum ore) is ground together with cement to produce high alumina cement. This can
be especially used in infrastructure where fast repair is needed such as pavement to avoid
long traffic obstruction. Also, can be used in the prestressed concrete plant to remove the
formwork quickly.
However, as much as concrete has so many advantages in the field of construction
industry, it also has some serious limitations. The contribution of greenhouse gases like
CO2 and NOx from concrete industry is more than 8% in total and is expected to grow in
2050, as the demand will be more than double. This is a significant issue that needs to be
addressed as quickly as possible. Our earth’s climate is degrading day by day and has
already reached the irreversible stage, thus the only way would be to stop it from getting
worse than it already is.
Researchers have been going for years for an alternative to cement, to make the
construction industry more sustainable. Use of industrial waste such as: Fly ash, silica
fume, sewage sludge, GGBFS and agricultural waste such as: Rice husk ash, Palm oil fuel
ash, Bagasse ash, wood waste ash, bamboo leaf ash, and corn cob ash has been partially
replacing cement to improve its properties and making it more durable and sustainable.
Modern technologies have grown every day to save our environment and we must continue
to do this until we achieve our goal.
Use of industrial and agricultural waste to partially replace cement has been an
effective way to make concrete more sustainable, but this replacement reduces the early
strength of concrete. And again, many research has been going on to compensate the early
strength of concrete when these industrial wastes such as Fly ash and GGBFS are used.
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Use of silica fume and metakaolin has been able to compensate some strength factors such
as abrasion resistance and increase in microhardness at an early age.
Similarly, this thesis is also a small effort towards more sustainable and durable
concrete and incorporating nanotechnology in concrete has helped to do so. Nano CaCO3
used in this project not helps to compensate the strength loss due to the addition of fly ash
but also helps in consuming more CO2. 98% pure CO2 is passed through liquid calcium
hydroxide to make precipitated calcium carbonate whose size could range from micro and
nano of a meter. Thus, this idea could be incorporated in utilizing the CO2 produced during
cement manufacture and pour the same nano CaCO3 in the clinkering zone to make a new
type of cement, that would be more sustainable and durable than the ordinary cement.
Overview of thesis
This thesis is divided into seven main chapters that have its own objective in
addressing the specific part of research that was conducted.
Chapter 1 includes the abstract of the research that provides a summary of the
research that was done and some critique results that were observed. This chapter also gives
an idea of the objective of research that includes the manufacturing process of cement and
different type of cement that has been produced for a different application.
Chapter 2 articulates the background of research done in the area of nanoparticles
and supplementary cementitious materials used in construction industry till date.
Chapter 3 provides the research overview that has been done in this field till date.
This chapter also includes the limitations and advantages of the all the materials that have
been used to improve the performance and sustainability of concrete.
Chapter 4 has the specifications and properties of all the materials that have been
used including the mill certificate for the Portland cement and Fly ash used, the gradation
of coarse and fine aggregates and the specification of nano CaCO3 used.
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Chapter 5 includes all the specification of test including the step by step procedure
used to conduct a test on fresh and hardened concrete.
Chapter 6 consists of all the test results which are tabulated and plotted for better
understanding. This chapter also discusses the test results giving us an idea about the
efficiency of this research.
Chapter 7 includes the summary of research including some outstanding results that
were produced during the experimental investigation of our project.
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CHAPTER II
LITERATURE REVIEW
This section comprises a summary of research studies done in the field of concrete
materials including supplementary cementitious materials and use of nanotechnology in
concrete.
Supplementary cementitious materials (SCMs)
Supplementary cementitious materials (SCMs) are used along with Portland cement
to improve and change the properties of concrete as suited with different applications. They
are either hydraulic or pozzolanic materials.
Figure 2.1 Left to Right: Class C fly ash, Metakaolin, Silica fume, Class F fly ash, Slag, Calcined shale. (THE
CONCRETE COUNTERTOP INSTITUTE, n.d.).
Hydraulic materials are material that, in finely divided form and in the presence of
moisture react with water to form cementitious material. GGBFS blended Portland cement,
calcium aluminate cement, are some of the examples of hydraulic cementitious material.
The pozzolanic material is siliceous or alumino-siliceous material that, in finely divided
form and in the presence of moisture chemically reacts with calcium hydroxide released
by the hydration of Portland cement to form compound possessing cementitious properties.
Fly ash, silica fume, metakaolin, rice husk ash, etc. shows pozzolanic properties.
C3S + H CSH + CH
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CH + Pozzolan(S) CSH (calcium silicate hydrate)
Hydraulic materials react faster than pozzolanic materials, as pozzolanic materials
would have to wait for cement hydration to produce calcium hydroxide. Presence of
calcium hydroxide reduces the concrete strength. Thus, use of pozzolanic materials would
help to increase the later age strength of concrete by utilizing calcium hydroxide present in
the concrete. However, hydraulic materials provide higher early age strength as the rate of
hydration would be faster than in ordinary concrete but, these materials would not help
much for later age strength of concrete.
Some of the widely used Supplementary cementitious materials are discussed in the
section below:
Fly Ash
Fly ash is used as supplementary cementitious material to replace cement in the
production of concrete. Although the use of Fly ash was initiated in the early 19’s, however,
significant utilization started during mid 19’s (FHWA, 2016).
Figure 2.2 Typical class C Fly ash (Alibaba, n.d.).
Fly ash is a byproduct of burning pulverized coal or bituminous coal in an electrical
generating station. Moreover, it is the unburned residue that is carried away from the
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burning zone in the boiler by flue gases and then collected by either mechanical or
electrostatic separators (FHWA, 2016). It is finely divided amorphous aluminosilicate with
varying amounts of calcium. The performance of fly ash concrete depends on physical,
mineralogical, and chemical properties of fly ash. The mineralogical and chemical
composition depends on the composition of coal, its sources and collection methods. The
calcium content is probably the best indicator of how concrete will behave with the addition
of fly ash. Depending on the amount of calcium content, fly ash is divided into two
categories: Class “C” and Class “F” Fly ash. Both have their own advantage and
limitations.
ASTM specification for Fly Ash
Class “F” Fly ash: Fly ash normally produced from burning anthracite or
bituminous coal that meets the applicable requirements for this class as given herein. SiO2
+ Al2O3 + Fe2O3 ≥ 70%. This class of fly ash has pozzolanic properties.
Class “C” Fly ash: Fly ash normally produced from lignite or sub-bituminous coal
that meets the applicable requirements for this class as given herein. SiO2 + Al2O3 + Fe2O3
≥ 50%. This class of fly ash, in addition, to having pozzolanic properties, also has some
cementitious properties as calcium content is higher.
The other limit placed on the composition of fly ash by ASTM is maximum
allowable loss-on-ignition (LOI), which indicates the presence of unburnt carbon. The limit
in ASTM is 6% for class F and class C fly ash, however, the specification allows class F
fly ashes up to 12% LOI (FHWA, 2016). Higher the amount of unburnt carbon, higher will
be the need of air entraining agent, as the carbon adsorbs the entrained air making it
unavailable to stabilize air bubbles.
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Effect of fly ash on the properties of fresh concrete:
Workability
Increase in the workability of concrete even with low w/c ratio is one of the key
property improved with the use of high-quality fly ash. This is due to the morphology of
fly ash; the perfect spherical shape of this particle improves the workability by the ball-
bearing effect. Figure 2.3 shows the morphology of fly ash. Thus, a well-proportioned fly
ash concrete will have improved workability when compared with ordinary concrete of the
same slump. This means that, in a given slump, fly ash consolidates and flows better than
a conventional concrete.
Figure 2.3 Morphology of Fly ash (Won, 2016).
Bleeding
Fly ash reduces the amount and rate of bleeding as the water demand is reduced
due to improved workability. Amount of bleeding in the freshly placed concrete increases
the risk of plastic shrinkage reducing the durability of infrastructures. Increase in
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workability facilitates in reducing water-cement ratio, thus reducing the overall water
content in the concrete which in turn decreases the amount of bleed water.
Air entrainment
Air entraining agent is essential to protect concrete from freeze and thaw. Entrained
air helps in reduction of expansion of concrete during freezing allowing water to escape
into the entrained voids. Depending upon the mineralogical composition of fly ash, the
dosage of air entraining agent fluctuates. Lower the LOI percentage, lower will be the
amount of unburnt carbon, thus dosage of air entrainment agent reduces. However, the
presence of unburnt carbon absorbs air present in the concrete increasing the dosage of
admixture.
Setting time
The setting behavior of fly ash concrete depends upon the amount of cement
replaced, a weather condition at the time of placement, the calcium content of fly ash, w/c
ratio, the type and amount chemical admixture used.
During hot weather, the retardation of setting time due to fly ash reduces, as the
rate of hydration increases. Similarly, fly ash containing high calcium contains reduces the
setting time due to increase in the rate of hydration. However, chilly weather, less calcium
content fly ash and increase in the replacement rate increases the setting time abundantly.
Heat of hydration
Increase in heat of hydration increases the core temperature of concrete causing
early age cracking in massive structures, reducing its durability. Thus, it is extremely
important to maintain the rise in core temperature of concrete while placing for massive
structures. Concrete with low Portland cement and high fly ash content are particularly
suitable for minimizing autogenous temperature rises. HVFA concrete mixes with class F
fly ash is effective in reducing both rates of heat development and the maximum
temperature reached within the concrete (Michael Thomas). Reduction in cementitious
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materials in concrete helps in reduction of maximum temperature rise in concrete due to a
reduction in rate and heat of hydration. Thus, class C fly ash with high calcium content
would be less effective to improve autogenous temperature rise (FHWA, 2016). However,
they do help in increase in the early strength of concrete.
Effect of fly ash on the properties of hardened concrete
Compressive strength
Fly ash reduces the early age strength of concrete significantly with the increase in
replacement levels of fly ash. This is because pozzolanic reactions are slower than the
hydraulic reactions. However, later age strength will be improved dramatically as the
calcium hydroxide present in the concrete would be reduced to calcium silicate hydrate, a
key factor responsible for the strength of concrete. The rate of early strength is strongly
influenced by temperature, as pozzolanic reactions are sensitive to temperature than
hydraulic reactions. Similarly, calcium content in the fly ash also plays a significant role
in early strength, as it contributes to more hydration of concrete. Researchers have also
shown that if temperature matched curing is to be done, the early strength of fly ash
concrete would be more compared that of ordinary concrete (Michael Thomas).
Creep
Creep would be low in fly ash concrete if loaded at an age when they have attained
the same strength as ordinary concrete as strength gain in fly ash concrete continues.
However, if the fly ash concrete is to be loaded at an early age, then the creep would be
higher than traditional concrete (Michael Thomas).
Drying shrinkage
Amount of water present in the mix and fractional volume of aggregate are the
factors that affect drying shrinkage. Higher the w/c ratio, higher will be the drying
shrinkage and lower the fractional volume of aggregate higher will be the drying shrinkage
as aggregate does not shrink as much as compared to the paste in concrete. In well cured
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and properly proportioned fly ash concrete, where w/c ratio has been decreased to maintain
the same slump as for ordinary concrete, drying shrinkage is lower than for the ordinary
concrete (Michael Thomas).
Effect of fly ash on the durability of concrete
Abrasion resistance
Abrasion resistance mainly depends on the properties of aggregate and strength of
concrete regardless the presence of fly ash. However, fly ash concrete with stronger
aggregates have proven to be more resistant towards abrasion with the increase in the age
of concrete than ordinary concrete due to increasing strength gain (Michael Thomas).
Permeability and resistance to the penetration of chlorides
The permeability of fly ash concrete decreases phenomenally with the increase in
age of concrete. Thus, at later age, HVFA concrete has very low permeability compared to
that of ordinary Portland concrete for same strength and environmental conditions (Michael
Thomas).
Alkali-Silica reaction
Decreased calcium and alkali content and increased silica content fly ash in
moderate replacement have proven to be the best effective way to mitigate the alkali-silica
reaction in fly ash concrete. This type of fly ash would reduce the risk of ASR more
effectively than the ordinary Portland concrete (Michael Thomas).
Sulfate resistance
Several studies have demonstrated the use of low calcium class F fly ash would be
more effective in providing better resistance to chemical attack. As the time increases, the
reduction of calcium hydroxide to calcium silicate hydrate makes concrete more compact
and less permeable, and the reduced w/c ratio of fly ash concrete helps to increase the
denseness of concrete with time. Thus, these properties increase the soundness of concrete
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providing better resistance to sulfate and another chemical attack. In contrast, fly ash
concrete that uses class C fly ash does not reduce the amount of CH, thus contributing less
to the soundness of concrete.
Carbonation
Carbonation of concrete is low for well cured, properly – proportioned concrete
with adequate cover provided for the embedded steel regardless of the amount of fly ash
used in concrete (Michael Thomas). Several studies also show that poorly cured fly ash
concrete will carbonate more compared to that of ordinary concrete with same curing
condition (Michael Thomas). The lime present in the concrete will reduce to calcium
carbonate reducing the strength of concrete.
Ca(OH)2 + CO2 Ca(CO)3 + H2O
Resistance to freeze and thaw
Concrete having an adequate air-void system, sufficient strength and frost resistant
aggregates can be resistant to freeze and thaw regardless of the amount of fly ash used
(Michael Thomas). However, the presence of unburnt carbon in the fly ash adsorbs the
entrained air and cannot be available to stabilize air bubbles, thus reducing the amount
entrained air voids (Michael Thomas). Thus, if fly ash with high unburnt carbon content is
to be used, then dosage of air entraining agent needs to be increased.
GGBFS
Slag cement also is known as ground-granulated blast-furnace slag (GGBFS) is also
an industrial waste that has been used in concrete industry for over 100 years now (FHWA,
2016).
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Figure 2.4 Typical GGBFS used in construction industry (Alibaba, n.d.)
Slag cement is produced from blast-furnace slag, which results from iron-ore in
blast furnace from iron. The iron ore and flux materials are continuously charged in the
furnace and the molten iron and slag are periodically separated and tapped off, then the
molten slag is quenched in water to form a glassy structure that is very much like the
ordinary Portland cement. Figure 2.5 shows the glassy structure of GGBFS under SEM
(Janardhanan, 2015).
Slag cement is more often used nowadays to produce blended cement, i.e., slag is
added to cement plant before cement clinkers are formed (FHWA, 2016). This type of
cement has equivalent properties to that of Type IV cement. The rate of hydration and heat
of hydration is reduced thus decreasing autogenous temperature rise in massive concrete
structure (FHWA, 2016).
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Figure 2.5 Morphology of GGBFS under SEM (Janardhanan, 2015).
Slag cement is hydraulic and produces calcium silicate hydrate with water, but the
reaction is slower than that of ordinary Portland cement. Even though slag is hydraulic
cement, it does consume CH produced by Portland concrete by binding alkalis in its
hydration products (FHWA, 2016). Thus, giving benefits to both hydraulic and pozzolan
cement.
Slag cement affects both the properties of fresh and hardened concrete. The blended
does have good workability over Portland cement with same w/c ratio but is not as effective
as fly ash due to its glassy structure. Fly ash has perfect spherical like structure offering
greater workability, consolidation, and placement of concrete than slag.
Curing of slag-based cement concrete is very crucial than ordinary concrete as the
hydraulic reaction is very low for slag cement (FHWA, 2016). Thus, also increases the
setting time significantly (FHWA, 2016).
The lower reaction rate, especially at a lower temperature is often overlooked which
could lead to durability issues and at the same time the slower reaction of blended cement
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can be used as an advantage for mass concrete structures to reduce the maximum rise in
core temperature (FHWA, 2016).
Slag cement binds alkalis in its CSH reaction products and utilizes CH to produce
CSH, thus densifying the concrete structure and reducing the alkali content and making it
less permeable. Hence, slag cement is more resistant towards ASR and external sulfate
attack with the higher replacement of more than 50% (FHWA, 2016).
Rice Husk Ash (RHA)
RHA is an agricultural waste product that has now been widely used as SCM
especially in an agricultural country with a higher production of rice. RHA has higher
amount silica content, less amount of calcium and alkali content when ground finely
attribute a lot of special properties when used as a replacement for cement (Ravinder Kaur
Sandhu, 2016).
RHA is a super good pozzolanic material because of the high content of silica. The
properties of concrete improved by RHA is like that of Fly ash, except for the workability
which is reduced with the increased in replacement level of finely grounded RHA.
Figure 2.6 Several stages of Rice Husk Ash (Thomas, 2018).
Nano silica is a finer form of RHA which is said to improve the compressive
strength, aggregate paste bonding, permeability, split tensile strength, and abrasion
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resistance. (Ehsani, 2016) But, the production of nano silica is extremely expensive
limiting its use in construction industry.
Pumice
Pumice was used in concrete throughout history even in ancient times during
Roman and Greek civilizations. However, the price and availability of fly ash made it more
economical than pumice (Saamiya Seraj, 2017). Pumice is formed from highly siliceous
volcanic lava. The hot lava quickly cools down to form a glassy structure called pumice.
Pumice is suitable to use as SCM due to its amorphous structure and high silica content
(Saamiya Seraj, 2017).
Figure 2.7 Typical volcanic ash (Geology, n.d.).
With the rising demand for SCM, there has been renewed interest to use pumice,
natural pozzolans an alternative to meet the demand. Researchers have evaluated the
performance of pumice mixtures in terms of compressive strength, durability, and mixture
workability (Saamiya Seraj, 2017).
Some examples of US massive structures with pumice are Los Angeles aqueduct
in 1912, the Friant dam in 1942, the Altus dam in 1945 and the Glen Canyon Dam in 1964
(Saamiya Seraj, 2017).
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Finely ground pumice, as a natural pozzolan gives better early strength compared
to fly ash and GGBFS as the finer particles act as nucleation for early hydration of cement.
Also, the increased pozzolanic activity also helped in densifying the CSH and making the
concrete low permeable. However, the later age strength was found to be reduced with time
(Saamiya Seraj, 2017). Workability was also reduced significantly as the size of pumice is
finer than Fly ash or GGBFS absorbing the moisture making it little available for paste.
Silica Fume
Silica fume is sub-micron by-product formed in electric arc furnace during the
production of metallic silicon or ferrosilicon alloys. Silica fume is one of the most popular
super pozzolans that consists of 90% silica. Most particles are smaller than 1-mm with an
average diameter of 0.1 mm. Silica fume can replace Portland cement in the range of 9-
15% by mass of cement. However, increase in replacement by more than 15% will result
in negative effects on concrete (FHWA, 2016). Silica fume is often found to be black or
gray in color due to heavy content of carbon and iron.
Commonly, silica fume is used in the ternary blend to improve the properties of
concrete. Finer silica fume helps to densify the CSH and increase the rate of hydration at
early stages with a major reduction in workability. Thus, if silica fume is to be used with
Fly ash or GGBFS, then this ternary blend would compensate the loss in early age strength
due to fly ash and reduced workability due to silica fume.
The advantages of using silica fume are increased pore refinement, improved
strength at an early age, stickiness, ASR resistance and enhanced sulfate resistance
(Aprianti, 2016). Increase in surface area due to fineness increases the amount of water
needed in the mixture, so it is recommended to use water- reducing admixture (Aprianti,
2016). Figure 2.8 shows the denseness of silica fume under SEM.
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Figure 2.8 Morphology of Silica Fume under SEM (Pittsburgh Mineral and Environmental Technology, Inc, n.d.).
Abrasion resistance is one of the factors to be considered during the construction
of industrial floors, rigid pavement, or other surfaces on which friction forces are applied
due to relative motion between the surface and moving object. Abrasion resistance depends
on environmental condition, aggregate type, amount of aggregates, mixture proportion, use
of SCM, the strength of concrete. Numerous studies show an increase in abrasion resistance
with an increase in replacement level of Silica fume up to 30%. However, the use of water
using admixture is inevitable while using silica fume. Moreover, the price and less
availability of silica fume make it uneconomical.
Metakaolin
Metakaolin is aluminosilicate material that helps to improve the properties of
concrete through micro filler effect and pozzolanic activity, i.e., reacts with slaked lime
produced during hydration of concrete to form calcium silicate hydrate.
Metakaolin is produced by dehydrating kaolin clay in between 650-700oC in an
externally fired rotary kiln into fine particles having an average diameter of less than 1-
mm. These are also called High reactive metakaolin (HRM), as it reacts very quickly due
to increase in surface area and reactivity of particles. Studies have also shown that HRM
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is responsible for acceleration in the hydration of ordinary Portland cement and its impact
can be seen within 24 hrs. This also reduces the deterioration of concrete by ASR, as the
HRM reduces the amount of lime significantly making concrete less permeable and
stronger. As metakaolin is produced by calcination of purified clay that is used in the
making of china clay, they are white in color. The microstructure of metakaolin is shown
in the Figure 2.9 below.
Figure 2.9 Morphology of Metakaolin under SEM (Hindawi, n.d.).
Although HRM is a pozzolan material like fly ash, the strength at an early age is
increased due to a higher rate of pozzolanic reaction than compared to fly ash. Research
shows the rate of reaction of Metakaolin with calcium hydroxide was almost double than
fly ash and calcium hydroxide reaction.
Increase in the dosage of superplasticizers, a higher price than ordinary Portland
cement, higher dosage to obtain better improvement makes metakaolin an expensive
choice. Moreover, there has been little research done in the field of the behavior of
metakaolin concrete under sustained load which makes us skeptical to use metakaolin
based concrete in massive structures
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Sewage sludge ash
Utilization of sewage sludge ash to replace the mass of cement. would decrease the
amount waste production making environment greener and safer. Sewage sludge ash is the
byproduct produced during the combustion of dewatered sewage sludge in an incinerator.
It is primarily a silty material with some sand-size particles. The specific size range and
properties of the sludge ash depend on the type of incineration system, the source of sludge
ash, and the chemical additives introduced in the wastewater treatment process.
Less research has been done in this area, but if used as an SCM meeting the ASTM
specification, sewage sludge ash has high potential in improving the properties of concrete.
Improved concrete durability, workability, and sustainability of these
supplementary cementitious material have led to a high increase in demand for fly ash and
GGBFS. However, new environmental regulations in different countries have an impact
on the availability of these materials. The source for class “F” fly ash reduced significantly
as the use of coal reduces in the industry. Thus, many researchers are now studying the use
of more natural pozzolans such as; volcanic ash, rice husk ash, palm oil ash, and sewage
sludge ash. These materials have shown the possibility of replacing fly ash and GGBFS.
Moreover, the decrease in early strength is another limitation of SCM. Due to
slower pozzolanic reactions, the rate of strength gain is reduced thus increasing the time of
construction. Different other materials such as; metakaolin and silica fume have been
incorporated to reduce the early strength of high volume fly ash concrete. But, high price
and less availability make these materials uneconomical. Also, the use of superplasticizers
is a must for concrete incorporated with silica fume and metakaolin due to a significant
reduction in a slump. Use of superplasticizers increases the demand of air entraining agent,
thus making it more unsuitable for places prone to freeze and thaw damage.
High volume fly ash is becoming more popular for massive structures as it helps to
reduce autogenous temperature rise in concrete. In contrast, incorporation of silica fume
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and metakaolin increases the autogenous shrinkage in concrete making it unsuitable for
massive concrete pours.
Use of nanotechnology in concrete has seen a positive possibility in improving the
limitations due to the incorporation of different SCM materials. Nano SiO2 has helped to
improve the early strength of high volume fly ash concrete dramatically without an increase
in autogenous shrinkage. The reactivity of nanoparticles is higher due to a decrease in
particle size, thus increasing the rate of hydration. Researchers have shown that the
pozzolanic reactions are faster in nano incorporated concrete. This property would also
help in increase in the use of natural pozzolans for improved concrete properties.
Nano Concrete
Nanotechnology has been a great area of interest, as these tiny materials have been
able to change the mechanical properties of concrete to a large degree. There has not been
any nanotechnology used commercially so far in construction except for Nano SiO2, which
is produced by grinding rice husk ask very finely to form nano-sized materials. However,
these materials are not as cost-effective and abundantly available as other SCMs. But, if in-
depth research is to be done in this area, there is a possibility of new tech ultra-high
performing, sustainable, economical and durable concrete.
Nano SiO2, Nano TiO2, Nano ZrO2, carbon nanotubes, carbon nanofibers, Nano
CaCO3 has some great possibility in the field of Nano concrete (Hanus, 2008). These
materials tend to change the DNA of concrete by changing the composition of calcium
silicate hydrate. “Smart concrete” and “self-sensing concrete” are getting their way into the
construction industry as they can get the health status of concrete periodically with
deconstructing the infrastructure thus giving us the signal before the fall of any huge
structures (Hanus, 2008).
As much as these materials seem to have ultra-high performing properties, use of
nanotechnology in commercial construction is very slim. Nano TiO2 is used abundantly in
countries like Japan. Similarly, nano SiO2 has been emerging as potential SCM with unique
properties but due to the less commercial application, the price is still expensive. Moreover,
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CNFs and CNTs are not commercially available yet. Researchers are trying to create more
sustainable and economical way to produce these nanoparticles. Current market values for
different SCM and nanomaterials is provided in the table below.
Table 2.1 Materials price sourced from Alibaba and eBay website
Materials Price per Ton
Nano calcium carbonate $60 - $150
Nano silicon dioxide $7000 - $10000
Metakaolin $300 - $500
Silica fume $500 - $1000
Fly ash $15 - $70
Ordinary Portland cement $50 - $75
In contrast, nano calcium carbonate has a wide range of applications in medical,
pharmaceutical, and different other industry making it widely available. Price of nano
calcium carbonate, as shown in Table 2.1, is less than that of ordinary Portland cement.
Also, the production of nano calcium carbonate utilizes CO2 making it more sustainable.
Use of nano calcium carbonate not only act as filler in concrete, the calcium content also
helps in providing cementitious properties to high volume fly ash concrete. Similarly, the
rate of hydraulic reaction is faster than for the ordinary Portland concrete. Thus, this study
has been a step towards producing economical, sustainable, durable and high-efficiency
concrete with the use of nanomaterials.
Nano Calcium carbonate
Nano calcium carbonate (Nano CaCO3), is another nanoparticle that has been
produced commercially for the medical, and other industry but has not been used
commercially in the construction industry. However, these tiny white particles have been
shown to improve the mechanical properties of concrete dramatically (Faiz U.A. Shaikh,
2014). This thesis describes the test done to observe the change in properties of ordinary
concrete and fly ash concrete with the addition of nano calcium carbonate and it has shown
to improve several properties of concrete including durability and strength.
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Figure 2.10 Schematic figure to produce nano calcium carbonate (Eda Ulkeryildiz, 2016).
Different technologies have been emerging to produce rice like hollow nano
calcium carbonate in the sustainable and efficient way and make it more economical.
Normally, 98% pure carbon dioxide is passed through liquid calcium hydroxide, that is
continuously stirred to produce precipitated nano CaCO3 (Eda Ulkeryildiz, 2016). The
schematic figure to produce nano calcium carbonate is shown in Figure 2.11. Similarly,
different shapes and size of nano calcium carbonate can be produced by altering the
pressure of carbon dioxide into the solution, the speed of agitation of solution, and different
pH (Gupta, 2004). Figure 2.12 shows varied sizes of nano calcium carbonate produced.
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Figure 2.11 Varied sizes of nano calcium carbonate (Gupta, 2004).
The production of calcium carbonate nanoparticle makes it more sustainable by
utilizing CO2. This idea could be incorporated in the concrete plant to utilize CO2 produced
during calcination process and produce nano CaCO3 which could be added in the clinkering
process to react with cement clinkers making the reaction faster and reducing the
temperature. Hence a new type of cement could be produced by this process that will have
better-performing cement than the ordinary cement with the expense of reduced heat
energy and reduced CO2 production.
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CHAPTER III
MATERIALS
This section describes all materials used to produce concrete specimens for property
evaluations. Coarse aggregate, fine aggregate, ordinary Portland cement, and fly ash were
sourced from a nearby concrete plant located in Lubbock. However, nano calcium
carbonate was ordered from China through Alibaba website.
Coarse Aggregate
Coarse aggregate used in this project is limestone which is lighter than gravels or
other crushed stones. ¾ inch nominal maximum size conforming to ASTM C 33-86 was
used. Absorption, moisture content, specific gravity, and sieve analysis test were conducted
to identify different properties of coarse aggregate using ASTM procedures.
Table 3.1 Properties of Coarse Aggregate
Properties Values
Specific gravity 2.4
Absorption 0.8%
Moisture content 2%
Gradation Grade 5
Fine Aggregate
Siliceous river sand was used for this project. It met all the performance requirements
conforming to ASTM C33-86. Similarly, specific gravity, absorption, moisture content,
and sieve analysis test were performed to identify different properties of fine aggregate
using ASTM procedures.
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Table 3.2 Properties of fine aggregate
Properties Values
Specific gravity 2.5
Absorption 0.3%
Moisture content 3.8%
Fineness modulus 2.6
Fly Ash
Class “C” fly ash was used which was sourced from a local concrete plant from
Lubbock, Texas. The mill certificate given in the appendix, the summary of which is
illustrated in Table 3.3, shows mineralogical composition of this fly ash.
Table 3.3 Composition of Fly ash
Ordinary Portland cement
One type of Portland cement was used throughout the project. Type I/II ordinary
Portland cement meeting ASTM C150-86 requirements was used, and the mill certificate
given in the appendix show mineralogical composition of this cement. All specimens were
cast during March 2018.
Composition Values (%)
SiO2 35.58
Al2O3 18.27
Fe2O3 7.38
CaO 25.88
MgO 5.27
SO3 1.43
Moisture content 0.07
Loss on ignition 0.2
Eq. Na2O 2.15
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Nano Calcium Carbonate
Nano calcium carbonate was ordered from China through Alibaba website. 98% pure
white precipitated nano CaCO3 has an average diameter of 40 nm. Table 3.3 provides the
properties of nano calcium carbonate provided by the seller from China.
Table 3.4 Composition of nano CaCO3
Properties Values
Moisture content <0.5
Surface area >40 m2/g
Average size 40 nm
CaCO3 % >95
Mg0 % <0.5
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CHAPTER IV
METHODS
This section includes all the procedure and methods used in conducting a different test
for the experimental investigation. Ordinary Portland cement was replaced by 35% (F35)
and 45% (F45) fly ash by mass of cement. F35 and F45 were further modified by replacing
1%, 3%, and 20% of cement with nano calcium carbonate. Concrete mix design for all the
samples is attached in the appendix. The test matrix is shown in Table 4.1.
Table 4.1 Design matrix
Nano CaCo3 Fly ash
0 0
1 35
3 45
20 -
Properties of coarse aggregate
Tests were conducted to identify different properties of coarse aggregate such as;
absorption, moisture content, specific gravity and sieve analysis using ASTM procedures.
All the procedures are further explained in detail in the sections below.
Absorption and specific gravity of coarse aggregate
Absorption and specific gravity of coarse aggregate were conducted in accordance with
ASTM C127 procedures:
✓ Samples were immersed in water for 24 hours.
✓ Samples were then removed from the water and was air dried using a cotton cloth
and cold air to bring it to the saturated surface dry condition.
✓ Then, the mass of sample was recorded in saturated surface dry condition (Mair).
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✓ After determining the mass in air, samples were immediately placed in a container
and apparent mass in water was recorded (Mwater).
✓ Finally, the samples were oven dried at a temperature of 108oC for 24 hrs. and was
weighed again (Movendried).
✓ Following formulas were used to calculate absorption and specific gravity of coarse
aggregates.
Specific gravity = Movendried/ (Mair - Wwater)
Absorption = (Mair - Movendried) / Movendried x 100 (%)
Absorption and specific gravity of fine aggregate
Absorption and specific gravity of coarse aggregate were conducted according to
ASTM C127 procedures:
✓ Samples were immersed in water for 24 hours.
✓ Samples were then removed from the water and was air dried using a cotton cloth
and cold air to bring it to the saturated surface dry condition.
✓ Pycnometer filled with water up to the calibration mark was weighed (B).
✓ The saturated surface dried sample was weighed (A) and then introduced in the
pycnometer and water was again filled up to the calibration mark (C).
✓ The mass of sample was recorded in saturated surface dry condition (S).
✓ The remaining sample was then oven dried at a temperature of 108oC for 24 hrs.
and was weighed again (O).
✓ Following formulas were used to calculate absorption and specific gravity of coarse
aggregates.
Specific gravity = A/ (B+A-C)
Absorption = (S- O) / O x 100 (%)
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Moisture content for coarse and fine aggregate
Moisture content for coarse and fine aggregate was conducted following ASTM C566
procedures:
✓ 500gm of the sample for fine aggregate and 1000gm of coarse aggregate was oven
dried for 24 hrs. at 105oC.
✓ Oven dried samples were then weighed to calculate the moisture content.
✓ Following formulas were used to calculate absorption and specific gravity of coarse
aggregates.
Moisture content = (Mass of the sample - Mass of oven dried sample)/Mass of oven
dried sample x 100 (%)
Sieve analysis for coarse and fine aggregate
Sieve analysis for coarse and fine aggregate was conducted following ASTM C136
procedures:
✓ Sieves with suitable openings are selected for both coarse and fine aggregates.
✓ 500gm of fine and 1000g of coarse aggregate was sieved in their respective
mechanical sieve shaker.
✓ Sieving was done for sufficient period such that not more than 1% by mass of the
material retained on any individual sieve will pass that sieve during 1 min of
continuous hand sieving.
✓ Percent retained, and percent passing was then calculated, and the gradation is
shown in the graph in the appendix.
Tests conducted on fresh concrete
Workability and finish ability of concrete is one of the most critical properties of
concrete. Concrete with low workability would not get in the commercial market even
though the strength parameters of concrete is good enough. Slump test, setting test, and the
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calorimeter test were done to study the change in fresh concrete properties after addition
of nano CaCO3.
Workability
Slump test is conducted following ASTM C143 procedures. A sample of freshly mixed
concrete was taken out for the slump test.
✓ This test was carried out in metallic mold also known as slump cone, that is open
at both ends and has attached handles.
✓ Cone was placed on a hard-non-absorbent surface and was filled in three layers
with fresh concrete by tamping each layer 25 times.
✓ The concrete was struck off at top of the cone to smooth out the surface and the
mold was lifted carefully vertically upwards.
✓ Finally, the slump of the concrete is measured by measuring the distance from the
top of the slumped concrete to top of the cone.
Setting time
Setting time was conducted following the ASTM C403 procedures.
✓ The fresh mortar was prepared using the concrete mixer, that has a minimum
capacity of 0.5 ft3.
✓ Bleed water was removed prior to the testing by using the plastic pipet and the mold
was tilted at 100 for the facilitation of bleed water.
✓ After an elapsed time of 4-5 hrs., the needle of appropriate size was inserted
depending upon the setting time of the mortar.
✓ Gradually and uniformly a vertical force was applied until the needle penetrates the
mortar at a depth of 1 inch.
✓ Time and force required to produce 1-inch penetration was recorded
✓ At least six penetration tests were done at an interval of ½ to 1 hr.
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Heat of hydration
X-Cal, a software that records and extracts the data for the heat of hydration of concrete
from semi-adiabatic calorimeter was used in conducting calorimeter test to study the rate
of increase in temperature during hydration of concrete. Following steps were followed:
✓ Four cylinders 4” by 8” were filled with fresh concrete and was stored in the semi-
adiabatic container.
✓ The cable connecting the container and the system with X-Cal software was
connected and the software was left for logging the data.
✓ After 72 hours of logging, the data was extracted from the software.
Tests conducted on hardened concrete
Hardened concrete properties help us to identify the behavior of concrete structures
under different environmental and structural loading. Soundness of concrete helps us to
identify the durability of structures. Different tests such as compressive strength, modulus
of elasticity, rapid chloride penetration test, and shrinkage ring test were conducted to
identify the properties of hardened concrete under different loading conditions.
Compressive strength
Compressive strength was conducted following ASTM C 39 procedures:
✓ Three moist cured specimens were prepared for each sample that met the specific
requirements mentioned in ASTM C39.
✓ The compressive strength of each sample was measured for 1 day, 3 days, 7 days
and 28 days respectively in a moist condition, i.e. immediately after it was taken
out of the curing tank.
✓ The bearing surface of the sample was cleaned, and bottom and the top bearing
plate was placed on top and bottom of the sample
✓ The sample was aligned with the axis of the testing machine.
✓ Testing machine was turned on and different properties of samples were entered,
and the rate of loading was fixed at 35 psi/s which was kept constant for all samples.
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✓ The load was then applied till the sample failed and the maximum load taken by
the sample was recorded.
Modulus of elasticity
Modulus of elasticity was conducted using free resonance testing device. Following
procedures were followed.
✓ Moist cured specimens were prepared for each sample.
✓ Modulus of elasticity was measured for 1 day, 3 days, 7 days and 28 days
respectively.
✓ The specimen was placed on a smooth surface, cable was connected at one end at
the center of the cylindrical specimen to record the frequency.
✓ Then, the other end was hammered slowly to record the frequency passed through
the specimen.
✓ Thus, the recorded frequency was used to calculate the modulus of elasticity for
each sample in wet condition.
Shrinkage Ring test
Shrinkage ring test was conducted following ASTM C1581 procedures:
✓ Steel ring with strain gages was set onto the base plate.
✓ The inner ring was centered with the 3 turnbuckles.
✓ The outer stainless ring was then set onto the base plate.
✓ Similarly, the outer ring was fixed with 2 turnbuckles in the same way as that for
the inner ring.
✓ The green steel beam was laid at last and was fixed with two threaded rods.
✓ The freshly mixed concrete mortar was used to fill the mold.
✓ The mold was filled in 2 layers, each layer was compacted 75 times using a 10 mm
diameter rod.
✓ The compaction was then finished off with a leveled surface with minimum
manipulation.
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✓ Coarse aggregate used in this test had a maximum size of 0.5”.
✓ After the completion of compaction, the turnbuckles and the butterfly nuts were
immediately loosened.
✓ After 2 minutes, the strain gage amplifier was connected to the data logger to the
data acquisition system, to record the time and begin monitoring strain gages at an
interval of 10 minutes.
✓ The sudden drop in the strain would indicate the time of the first crack.
Design matrix
Following design, the matrix was used to conduct the different test. Fly ash was used
at a replacement level of 35% and 45%. Similarly, nano calcium carbonate was used at
replacement level of 1%, 3%, and 20%.
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Table 4.2 Different notation used to differentiate samples.
Notation Definition
0 - 0 0% Nano Calcium Carbonate and 0% Fly Ash
0 - 35 0% Nano Calcium Carbonate and 35% Fly Ash
0 - 45 0% Nano Calcium Carbonate and 45% Fly Ash
1 - 0 1% Nano Calcium Carbonate and 0% Fly Ash
1 - 35 1% Nano Calcium Carbonate and 35% Fly Ash
1 - 45 1% Nano Calcium Carbonate and 45% Fly Ash
3 - 0 3% Nano Calcium Carbonate and 0% Fly Ash
3 - 35 3% Nano Calcium Carbonate and 35% Fly Ash
3 - 45 3% Nano Calcium Carbonate and 45% Fly Ash
20 - 0 20% Nano Calcium Carbonate and 0% Fly Ash
20 - 35 20% Nano Calcium Carbonate and 35% Fly Ash
20 - 45 20% Nano Calcium Carbonate and 45% Fly Ash
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CHAPTER V
RESULTS
This section presents the finding from various testing described previously investigate
the behavior of concrete as affected by the addition of nanoparticles.
Workability
Workability of fresh concrete was measured using slump test. Higher the slump,
better will be the workability of fresh concrete. However, higher slump also tends to
increase plastic shrinkage crack in concrete which decreases the durability of concrete.
Addition of 1% and 3% nanoparticles had little to no effect on the slump for concrete
without fly ash. However, the slump was reduced significantly for fly ash concrete after
the addition of nanoparticles. F35 and F45 slump were reduced by 2 inches and 2.5 inches
respectively after the addition of 3% nano CaCO3. Thus, the workability of normal concrete
with nano CaCO3 was not compromised without the decrease in a slump. On the other hand,
for high volume fly ash concrete, the slump was reduced significantly. A significant
decrease in bleed water was observed specifically for fly ash concrete. It appears that nano
CaCO3 blocks bleeding water in the concrete containing fly ash, as silica fume does,
resulting in decrease in workability. However, it is not known why the same phenomenon
is not observed in concrete without fly ash. Further investigation is warranted. Change in
a slump for the control sample, fly ash sample and sample with the addition of nano CaCO3
is shown in the Figure 5.1.
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Figure 5.1 Slump for different samples.
Setting test
The setting test is a measure of the rate of hydration of concrete and determines the
initial, and final sets, by evaluating penetration resistance of concrete. One of the main
disadvantages of using fly ash is the increase in setting time, thus elongating the time of
construction. However, use of nano CaCO3 has helped in decreasing setting time of high
volume fly ash concrete by up to 3 hours. Use of high volume fly ash is ideal for many
other applications such as in massive structure, but the prolonging setting times makes the
construction more challenging. Similarly, the final set of ordinary concrete was reduced by
up to 4 hours. The curvature of the setting test graph had a similar pattern for both ordinary
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concrete and fly ash concrete. The graph followed the same pattern until initial set, but the
slope was steeper after the initial set of samples with nano CaCO3, which indicated the
increase in the rate of hydration and/or stiffening of the cement matrix by small particles
of nano CaCO3. Penetration resistance for all samples is shown in the Figures 5.2 through
5.5. Red line indicates the initial set of concrete and blue lines indicates the final set of
concrete.
Figure 5.2 Penetration resistance for ordinary concrete, and 1% and 3% nano replacement in ordinary concrete
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Figure 5.3 Penetration resistance for F35, and 1% and 3% replacement of nano in F35
Figure 5.4 Penetration resistance for F45, and 1% and 3% replacement of nano in F45
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Figure 5.5 Setting time for all samples
Heat of hydration
The heat of hydration for all representative samples was observed using semi-
adiabatic calorimeter. Cylinders of size 4” by 8” were filled with fresh concrete and was
placed in the calorimeter. The heat of hydration was then recorded for 72 hours, and the
data was extracted using X-Cal software. This test is a measure of the heat of hydration
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produced during the hydration of calcium silicate hydrate. The Higher the heat of
hydration, the higher the rate of hydration, resulting in the decrease in setting times as
discussed above and potentially higher early strength. However, this was not true in the
case of concrete added with nano calcium carbonate. Although the rate of hydration was
dramatically higher for concrete with nano calcium carbonate as seen from the setting test,
the heat of hydration was lower than that for the control sample. However, the heat of
hydration was increased significantly for F35 with 3% nano calcium carbonate.
Figure 5.6 Heat of hydration for samples 0 – 0, 3 – 0, 3 - 35
Figure 5.6 illustrates the heat of hydration for different samples during the 72 hours.
Sample 1 is controlled sample which has the highest heat of hydration, i.e. 0% fly ash and
0% nano calcium carbonate. Sample 2 is 3% nano and 0% fly ash which has the slightly
lower heat of hydration than ordinary concrete. Similarly, sample 3 is 35% fly ash with 3%
nano calcium carbonate which has a higher heat of hydration, than sample 4, 35% fly ash
and 0% nano calcium carbonate. This shows the improvement in early hydration for 35%
fly ash concrete.
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Figure 5.7 Heat of hydration for samples 0 – 0, 1 – 0, 1 - 45
Similarly, Figure 5.7 represents control sample and fly ash concrete with 45%
replacement. Sample 1 with 0% fly ash and 0% nano calcium carbonate has the highest
heat of hydration. Sample 3 with 0% fly ash and 3% nano calcium carbonate has lower
heat of hydration than control specimen which contradicts with the expected rate of
hydration, which was higher for ordinary concrete with 3% nano calcium carbonate.
Similarly, sample 2 with 45% fly ash and 1% nano has shown to improve the heat of
hydration than sample 3 which is 45% fly ash with 0% nano calcium carbonate.
This indicates the potential of increase in early age strength without an increase in
autogenous temperature rise, unlike silica fume and metakaolin. This property can be
advantageous for pouring concrete into massive structures.
Compressive strength
Compressive strength has been most widely used as an indicator of the concrete
quality, since other durability properties are related to compressive strength, even though
the correlation is not as strong as desired. One great advantage of compressive strength
compared with other properties is that the time required for the evaluation of compressive
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strength is quite short and the testing itself is quite simple. Other advantages include rather
small testing variability, which is a requirement for any quality control testing. Concrete
strength includes the denseness, soundness, resistance to different chemical attack,
abrasion resistance, and many other factors. Compressive strength tests were performed on
cylinders cured for 1 day, 3 days, 7 days and 28 days. Addition of nano calcium carbonate
in ordinary concrete and in fly ash concrete improved early age compressive strength up to
98%. However, the later age strength varied according to the amount and type of fly ash
and nano CaCO3 used. The compressive strength of different samples for 1day, 3 days, 7
days and 28 days are shown in Figures 5-8 through 5-11.
Figure 5.8 Compressive strength for samples 0 – 0, 1 – 0, 3 - 0
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Figure 5.9 Compressive strength for samples 0 – 35, 1 – 35, 3 – 35
Figure 5.10 Compressive strength for samples 0 – 45, 1 – 45, 3 - 45
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Figure 5.11 Compressive strength for all samples
Elastic modulus
Modulus of elasticity determines the resistance of a material to elastic deformation.
The stiffer material has higher modulus. This is also defined by the slope of the stress-
strain curve in the elastic deformation curve. Modulus of elasticity reduced for ordinary
concrete with nanoparticles. Similarly, the modulus of elasticity was reduced for fly ash
concrete with the addition of nanoparticles. Usually, increase in compressive strength
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enhances the modulus of elasticity of concrete making it stiffer and more brittle. However,
the addition of nanoparticle increased the compressive strength of normal concrete and fly
ash concrete without a significant increase in elastic modulus. This finding is significant
since increased strength without the comparable increase in modulus would result in more
crack resistance concrete. This aspect of concrete material property modifications due to
the introduction of nano CaCO3 has significant practical implications and further
evaluations are warranted. Figures 5-12 through 5-15 present the variations in concrete
modulus with age for concretes evaluated in this study.
Figure 5.12 Elastic modulus for samples 0 – 0, 1 – 0, 3 - 0
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Figure 5.13 Elastic modulus for samples 0 – 35, 1 – 35, 3 - 35
Figure 5.14 Elastic modulus for samples 0 – 45, 1 – 45, 3 - 45
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Figure 5.15 Elastic modulus for all samples
Shrinkage Ring Test
This test was conducted to determine the resistance of concrete against shrinkage
cracking. The apparatus consists of an outer ring and an inner ring. Outer ring is removed
after the concrete is set. The inner ring has the strain gauges to measure the strain in ring
due to drying of concrete. Freshly mixed concrete was placed in the mold until the strain
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in the inner ring reduced by 30 microns or more. This indicates the occurrence of first crack
in concrete. Normally, ordinary concrete will have first crack due to drying shrinkage at
around 140 to 150 hours after the placement of concrete in the mold.
Figure 5.16 shows the strain values for ordinary concrete with 3% nano calcium
carbonate. It shows that a crack occurred at 209 hours after the concrete placement, and the
strain at the time a crack occurred was about 75 micro strain. To evaluate the crack
resistance of concrete containing nano CaCO3 with respect to the ordinary concrete, the
time it took for a crack to have occurred in this concrete has to be compared with that in
ordinary concrete. Preliminary testing for ordinary concrete indicated a cracking at much
earlier time. This shows the improvement in resistance of concrete towards drying
shrinkage crack. This can be related to increase in strength of concretes containing nano
CaCO3 without increased modulus of elasticity. As discussed earlier, this aspect of
improved crack resistance of concrete containing nano CaCO3 could have significant
practical implications and further efforts will be made to validate this initial finding.
Figure 5.16 Steel ring strain versus specimen age, days
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CHAPTER VI
DISCUSSIONS
This thesis describes the efforts made to investigate the effects of nano CaCO3 in
concrete on the modifications in the properties of concretes with and without fly ash.
Addition of 1% and 3% nanoparticles had little to no effect on the workability of concrete.
Fly ash concrete with nanoparticles reduced the slump and bleeding water.
In concrete with fly ash, the incorporation of nano CaCO3 increased the rate of
hydration, resulting in improved early strength. On the other hand, the heat of hydration
was slower for ordinary concrete with nanoparticles. These findings are somewhat
contradictory to the early-age strength variations. Further testing is needed to reconcile this
seemingly contradictory results.
Increase in early penetration resistance was observed with the addition of nano calcium
carbonate which is expected due to increase in the rate of hydration. This was due to the
faster reaction of nano calcium carbonate, increasing the rate of both hydraulic and
pozzolanic reactions.
Addition of nanoparticles improved the early age strength of fly ash concrete and
ordinary concrete due to a higher rate of hydration. However, later age strength depended
on many factors such as the type of fly ash used, amount of silica present in the fly ash,
amount of replacement. Concrete replaced with 35% fly ash along with nano calcium
carbonate displays significant improvement in compressive strength at an early age. In
contrast, 45% fly ash with nano calcium carbonate shows improvement of strength at an
early age and later age, later age strength being more prominent.
Early age strength is determined by the rate of reaction and later age strength is
determined by the amount and the bonding of calcium silicate hydrate. Size of
nanoparticles contributes to an increase in the rate of reaction due to the high reactivity of
the particles. Thus, the early age strength and early penetration resistance were improved
significantly for ordinary concrete and fly ash concrete with the addition of nanoparticles.
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Due to the combination of both pozzolanic and hydraulic reaction, the 28-day strength for
35 % fly ash was almost equal to the strength of control specimen. But, with the addition
of nano calcium carbonate, although the early age strength was improved, later age strength
was lower. This could be the result of the inappropriate ratio of calcium and silica content
present in the concrete, thus decreasing the amount of CSH formed. As the time increases,
the pozzolanic reaction increases depleting the amount of silica, accordingly less silica will
be available for complete hydration of calcium content. Thus, if the calcium and silica
content are well proportioned, then the nano calcium carbonate would perform better with
siliceous SCM such as class “F” fly ash, rice husk ash, and volcanic ash-producing high
performing nano concrete. These are hypotheses based on the observations of limited
testing results, and further evaluations are needed to confirm whether these hypotheses are
valid.
The limitation of using nano calcium carbonate is the inconsistency with the data due
to poor dispersion of particles. One of the main challenges would be to disperse the nano
calcium carbonate uniformly in the concrete mix due to its high reactive surface. Improper
dispersion would lead to bigger chunks of unreacted nanoparticles, decreasing the bond of
CSH and thus decreasing the strength of concrete.
As explained earlier, if the production of nano calcium carbonate was to be done in
the cement plant itself to produce blended nano cement, a new type of cement would be
formed that would be more sustainable and durable than ordinary Portland cement, while
solving the uniform dispersion issue.
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CHAPTER VII
SUMMARY & RECOMMENDATIONS
Nanotechnology has been an emerging topic in the field of concrete, as it helps to
improve the mechanical properties of concrete by changing the composites of calcium
silicate hydrate at the nano level. Some researchers have also shown the improvement of
early strength of High Volume Fly Ash concrete (HVFA) concrete after addition of
nanoparticles such as TiO2, nano SiO2, carbon nanotubes etc. Silica fume and Metakaolin
are the most commonly used SCM to improve the early age strength of HVFA concrete.
However, as much as these pozzolanic materials help to improve the impact resistance and
abrasion resistance, there has been trivial improvement in early age strength of HVFA.
This study presents the results of an experimental investigation conducted in
incorporating nano CaCO3 in HVFA to improve its early strength. Ordinary Portland
cement was replaced with class C Fly Ash at the level of 35% and 45% to produce HVFA.
F35 and F45 were furthered modified using nano CaCO3 at the level of 1%, 3%, and 20%.
All types of concrete mixtures were cured for 3, 7 and 28 days. Slump test, setting test, and
calorimeter test were conducted on fresh concrete. Similarly, compression test, elastic
modulus and shrinkage ring test were conducted on hardened concrete. Test results
indicated up to 20% increase in compression for HVFA mixed with nano CaCO3, and up
to 25% increase in compression for ordinary concrete mixed with nano CaCO3. However,
when cement was replaced with nano CaCO3, the elastic modulus was lower for both the
ordinary concrete and fly ash concrete. This finding has significant practical implications
since more crack resistant concrete can be produced with the introduction of nano CaCO3
without compromising structural capacity of the concrete elements. Similarly, the rate of
hydration increased with the addition of nano CaCO3, which contributed to higher early
strength of concrete.
Based on the observations of properties of concrete evaluated in this study with and
without nano CaCO3, it appears that the incorporation of nano CaCO3 in concrete could
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improve overall performance of concrete without sacrificing constructability and increase
in cost.
Different unique behaviors of concrete with nano CaCO3 must be furthered studied
and experimented thoroughly before reaching a concluding remark. As, this is a new area
of research, further extensive research of these materials can only lead us to definite
conclusion.
Moreover, this thesis was focused on early strength of concrete, more research is
needed to evaluate the durability of concrete with nano CaCO3. Material properties such as
resistant to ASR, sulfate attack, RCPT, drying shrinkage, behavior of nano concrete under
creep and sustained load needs to be further evaluated. Similarly, this study was
experimented only with class C fly ash but, use of nano calcium carbonate with more
siliceous pozzolans is another interesting area of research that could lead to further
improved concrete properties.
Furthermore, developing an optimum replacement level of nano calcium carbonate
for different types of concrete i.e., ordinary concrete, fly ash concrete, blended concrete
etc., is another critical issue that needs to be addressed to make this material commercially
feasible.
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THE CONCRETE COUNTERTOP INSTITUTE. Retrieved from
www.concretecountertopinstitute.com.
The science of concrete. Retrieved from http://iti.northwestern.edu/cement/index.html.
Thomas, B. S. (2018). Renewable and Sustainable Energy Reviews.
Won, D. M. (2016). Concrete materials class.
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APPENDIX
Table A 1 Sieve Analysis of coarse aggregates
Diameter
(mm)
Wt.
retained
(lbs.)
Percent
Retained
Cumulative
Retained
Percent
Passing
75.00 0.20 0.79 0.79 99.21
63.00 1.15 4.54 5.33 94.67
50.00 5.45 21.50 26.82 73.18
12.70 14.25 56.21 83.04 16.96
4.75 1.45 5.72 88.76 11.24
Pan 2.84 11.20 99.96
Figure A 1 Gradation of coarse aggregates used
0.0
20.0
40.0
60.0
80.0
100.0
120.0
01020304050607080
Per
cen
t fi
ner
Diameter (mm)
Coarse Aggregate
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Table A 2 Sieve Analysis of fine aggregates
Diameter
(mm) Wt
retained
(lbs.)
Percent
retained
Cumulative
retained
Percent
passing
4.75 6.13 0.85 0.85 99.15
2.36 43.04 5.94 6.78 93.22
1.18 113.98 15.72 22.50 77.50
0.60 231.01 31.86 54.37 45.63
0.30 205.97 28.41 82.78 17.22
0.15 91.21 12.58 95.36 4.64
Pan 17.34 2.39 97.75
Figure A 2 Gradation of fine aggregates
0
20
40
60
80
100
120
0.1 1 10
Per
cen
t fi
ner
Diameter (mm)
Fine Aggregate
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Table A 3 Mix design for all the samples
Mix Cement(lbs.) Coarse
Aggregate
(lbs.)
Fine
Aggregate
(lbs.)
Water
(lbs.)
Fly
ash
(lbs.)
Nano
CaCO3
(lbs.)
0-0 680 1745 1248 285 0 0
1-0 673 1745 1248 285 7 0
3-0 660 1745 1248 285 20 0
0-35 442 1745 1248 285 0 238
1-35 435 1745 1248 285 7 238
3-35 422 1745 1248 285 20 238
0-45 374 1745 1248 285 0 306
1-45 367 1745 1248 285 7 306
3-45 354 1745 1248 285 20 306
Table A 4 Setting time data for sample 0-0
Time (mins) Force (lbs.) Area (sq. in) Resistance (psi)
270 44 0.5 88
330 100 0.5 200
390 140 0.25 560
450 120 0.1 1200
580 185 0.05 3700
645 155 0.025 6200
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Table A 5 Setting time data for sample 1-0
Time (mins) Force (lbs.) Area (sq. in) Resistance (psi)
170 40 0.25 160
230 40 0.1 400
300 80 0.1 800
330 130 0.1 1300
360 132 0.05 2640
400 114 0.025 4560
Table A 6 Setting time data for sample 3-0
Time (mins) Force (lbs.) Area (sq. in) Resistance (psi)
180 40 0.5 80
240 84 0.25 336
285 100 0.1 1000
335 170 0.05 3400
355 110 0.025 4400
Table A 7 Setting time data for sample 0-35
Time (mins) Force(lbs.) Area (sq. in) Resistance (psi)
340 32 0.5 64
420 80 0.5 160
475 80 0.25 320
520 68 0.1 680
580 134 0.1 1340
640 120 0.05 2400
730 120 0.025 4800
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Table A 8 Setting time data for sample 1-35
Time (mins) Force(lbs.) Area (sq. in) Resistance (psi)
300 32 0.5 64
380 86 0.5 172
450 88 0.25 352
500 72 0.1 720
560 158 0.1 1580
620 142 0.05 2840
680 108 0.025 4320
Table A 9 Setting time data for sample 3-35
Time (mins) Force(lbs.) Area (sq. in) Resistance (psi)
300 38 0.5 74
330 52 0.5 102
400 56 0.25 220
445 38 0.1 380
485 86 0.1 860
540 98 0.05 1960
610 88 0.025 3520
655 118 0.025 4720
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Table A 10 Setting time data for sample 0-45
Time (mins) Force (lbs.) Area (sq. in) Resistance (psi)
300 22 0.5 44
360 38 0.5 76
470 60 0.25 240
510 90 0.25 360
590 78 0.1 780
650 66 0.05 1320
695 108 0.05 2160
755 100 0.025 4000
Table A 11 Setting time data for sample 1-45
Time (mins) Force(lbs.) Area (sq. in) Resistance (psi)
390 50 0.5 100
420 58 0.25 232
465 110 0.25 440
515 72 0.1 720
545 96 0.1 960
575 71 0.05 1420
605 118 0.05 2360
635 185 0.05 3700
660 120 0.025 4800
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Table A 12 Setting time data for sample 3-45
Time (mins) Force(lbs.) Area (sq. in) Resistance (psi)
360 34 0.5 68
420 38 0.25 152
540 96 0.25 384
580 174 0.25 696
620 120 0.1 1200
655 94 0.05 1880
685 130 0.05 2600
755 110 0.025 4400
Table A 13 Compressive strength for all samples for 1 day
Mix Compressive strength (psi) Average(psi)
0--0 1023 974 987 995
0--35 390 358 342 363
0--45 58 62 64 61
1--0 1900 1890 1810 1867
1--35 480 520 510 503
1--45 190 182 187 186
3--0 1880 1900 1856 1879
3--35 750 710 812 757
3--45 61 50 60 57
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Table A 14 Compressive strength for all samples for 3 days
Mix Compressive strength (psi) Average(psi)
0--0 3100 3000 3035 3045
0--35 2300 2200 2320 2273
0--45 2046 2035 2010 2030
1--0 3830 3780 3740 3783
1--35 2420 2460 2390 2423
1--45 2020 2035 2047 2034
3--0 3750 3788 3810 3783
3--35 2650 2600 2590 2613
3--45 1820 1800 1790 1803
Table A 15 Compressive strength for all samples for 7 days
Mix Compressive strength (psi) Average(psi)
0--0 4100 4150 4130 4127
0--35 3430 3487 3412 3443
0--45 3440 3448 3358 3415
1--0 5280 5235 5300 5272
1--35 3910 3930 3900 3913
1--45 4040 4008 4089 4046
3--0 4817 4800 4783 4800
3--35 4060 4048 4110 4073
3--45 3550 3678 3530 3586
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Table A 16 Compressive strength for all samples for 28 days
Mix Compressive strength (psi) Average(psi)
0--0 6650 6630 6665 6648
0--35 6660 6700 6670 6677
0--45 5500 5350 5420 5423
1--0 6950 6900 6890 6913
1--35 6500 6510 6480 6497
1--45 6780 6900 6820 6833
3--0 5450 5420 5410 5427
3--35 6100 6220 6180 6167
3--45 5700 5660 5675 5678
Table A 17 Elastic modulus frequency for all samples for 1 day
Mix Frequency (Hz) Average
0—0 8539 8319 8584 8480
0—35 8069 7968 7814 7950
0—45 7210 7175 7239 7208
1—0 8381 8552 8498 8477
1—35 7598 7667 7473 7579
1—45 7200 7154 7271 7208
3—0 8349 8243 8212 8268
3—35 7769 7681 7765 7738
3—45 7022 6926 6882 6943
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Table A 18 Elastic modulus frequency for all samples for 3 days
Mix Frequency (Hz) Average
0--0 9300 9248 9277 9275
0--35 8721 8612 8557 8629
0--45 8660 8531 8696 8629
1--0 9070 8930 9030 9010
1--35 8585 8444 8412 8480
1--45 8960 8967 8944 8957
3--0 8991 8983 9038 9004
3--35 8804 8731 8700 8745
3--45 8321 8333 8468 8374
Table A 19 Elastic modulus frequency for all samples for 7 days
Mix Frequency (Hz) Average
0--0 9398 9513 9550 9487
0--35 9328 9347 9150 9275
0--45 9202 9276 9188 9222
1--0 9560 9450 9520 9510
1--35 9350 9200 9275 9275
1--45 9249 9087 9171 9169
3--0 9578 9550 9333 9487
3--35 9200 9115 9192 9169
3--45 9088 9132 9128 9116
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Table A 20 Elastic modulus frequency for all samples for 28 days
Mix Frequency (Hz) Average
0--0 10030 10021 10001 10017
0--35 9859 9874 9841 9858
0--45 9644 9679 9615 9646
1--0 9700 9670 9730 9700
1--35 9588 9640 9671 9633
1--45 9800 9778 9837 9805
3--0 9743 9818 9800 9787
3--35 9720 9748 9698 9722
3--45 9569 9649 9561 9593
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Figure A 3 Slump test conducted for fresh concrete
Figure A 4 Preparation of sample for setting time
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Figure A 5 Compressive strength Testing machine
Figure A 6 Concrete mold after removal of outer ring for shrinkage ring test
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Figure A 7 Data logger used for shrinkage ring test
Figure A 8 Compaction of sample in the plastic mold for compressive strength and elastic modulus
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Figure A 9 Elastic modulus Test
Figure A 10 Semi-adiabatic calorimeter used for determining heat of hydration on fresh concrete