EFFECT OF NANO-SiO2 ON THE MECHANICAL

PROPERTIES OF CONCRETE

By

KEVIN JUAN

A Report Submitted in Partial Fulfilment of the

Requirement for the Degree of BEng (Hons) Civil
Engineering

Faculty of Engineering, Technology, and & Environment

UCSI University

2023

i
 ACKNOWLEDGEMENTS

This report would never have been complete if it wasn’t for the unyielding support and
contribution of many individuals and groups, named or otherwise. Finishing this long
and arduous journey in my academic career, I have far grown from the person I was
when I first set foot in Malaysia, and I could not have been any more grateful for that.
Among those without whose assistance and guidance I would never have completed my
studies are as follows:

First and foremost, I extend my heartfelt gratitude to my family and friends, for their
unending support, both financially and emotionally. Their guidance and patience have
carried me so far in persevering through the most difficult of times and have often
served as inspiration for my improvement as a person.

Special thanks are to Dr. Deprizon Syamsunur, for his supervision during my thesis,
proposal, and experiments. I am also grateful to Dr. Muhammad Noor Hisyam Bin
Jusoh, who greatly helped with the logistical aspect during the procurement of
experimental materials. Finally, I would also want to thank Mr. Firdaus as the block E
lab assistant, who has been a great help during my experiments.

In addition, I am also heavily indebted to many members and teachers of FETBE, who
provided me with a rich learning environment that stimulated my intellectual curiosity
and inspired me to go deeper into my field of study, going the extra mile in my studies.
The lectures I receive, as well as the critique and feedback I had received from my
esteemed professors in FETBE has shaped my mindset and character to become the
person I am today, and I will be in the future.

I want to also thank my former bosses in co-op, without whom I would not be properly
equipped with sufficient knowledge to complete my studies and consequently this
report.

In conclusion, I am humbled and grateful to all those who have contributed to this thesis
in various ways. Your support has been a cornerstone in my academic journey, and I
hope this work will contribute positively to the field and inspire further research and
discussions.

Thank you.

Kevin Juan

Kuala Lumpur, Malaysia

July 2023

ii
 DECLARATION OF ORIGINALITY AND EXCLUSIVENESS

I hereby declare that this report is based on my original work except for quotations and
citations which have been duly acknowledged. I also declare that it has not been
previously or concurrently submitted for any other degree at UCSI or other institutions.

……………………………………………..

KEVIN JUAN 1001954608

Date: 28.07.2023

Supervised by:

……………………………………………

ASST. PROF. IR. DR. DEPRIZON SYAMSUNUR

Date: 28.07.2023

iii
 ABSTRACT

Concrete has been a staple in civil engineering for a long period of time. Its combination
of strength, durability, and comparatively low costs has made it the most widely used
material for structural purposes. However, increasing consumer demands on building
performance and quality, coupled with increasingly stricter governmental regulations on
environmental concerns pressures the construction industry to innovate on the process
of concrete production, which undeniably causes a widespread negative impact on
environment. This study aims to analyse the potential of NS inclusion in concrete,
where previous studies on the subject indicated Nano-SiO2 inclusion can replace cement
in part by acting as a secondary source of Silica, a vital component in the hydration
process of concrete. Basis for this comes from previous tests done on NS concrete,
which generally show improvement in mechanical properties because of NS’ effects on
the microstructure, densifying and strengthening concrete. In most cases, previous
studies shown the optimal range of NS inclusion as ranging to 1.5% - 4.0%.
Experiments were conducted on 4 different concrete mixes, one control sample, three
samples which replace cement at 2.0%, 2.5%, and 3.0% percent weight of cement
respectively. This study analyses the performance, workability, and cost effectiveness of
each NS-infused mix and compares them to the control sample. 28-day results showed
that NS infused concrete had improved compressive strength by 20.09%, 11.93%,
34.41% for each mix. However, slump testing had indicated a significant loss in
workability, ranging from 59.38% for the NS20 mix upwards to 73.96% for NS30. For
its cost-efficiency, the performance increase from NS inclusion had outweighed the
extra cost required for NS mixes, where cost effectiveness goes up the higher degree of
NS concentration is used. In conclusion, the mix with 3.0% NS inclusion shown the
highest degree of improvement both in performance and cost-wise, albeit at the cost of
workability. However, future research still needs to be done on the safety measures for
NS usage in project sites, and on finding a way to methodically systemize NS inclusion,
as right now NS impact on concrete properties cannot be reliably projected by standard
design methods.

iv
 TABLE OF CONTENTS

ACKNOWLEDGEMENTS ii

DECLARATION OF ORIGINALITY AND EXCLUSIVENESS iii

ABSTRACT iv

LIST OF TABLES vii

LIST OF FIGURES viii

LIST OF ABBREVIATIONS AND SYMBOLS x

CHAPTER I INTRODUCTION 1

1.1 BACKGROUND 1
1.2 PROBLEM STATEMENT 4
1.3 SIGNIFICANCE 5
1.4 OBJECTIVES 5
1.5 RESEARCH SCOPE 6
1.6 METHODOLOGY 7
1.7 ORGANIZATION 8

CHAPTER II LITERATURE REVIEW 9

2.1 INTRODUCTION 9
2.2 MECHANICAL PROPERTIES OF CONCRETE 10
2.2.1 Compressive Strength 10
2.2.2 Flexural Strength 12
2.2.3 Tensile Strength 14
2.2.4 Durability 17
2.3 HYDRATION MECHANISM OF CONCRETE 18
2.4 GLOBAL ENVIRONMENTAL ISSUES 19
2.5 NANOMATERIALS AND NANOTECHNOLOGY 20
2.5.1 Nano SiO2 22
2.5.2 Nano CaCO3 23
2.6 INFLUENCE OF NANOMATERIAL ON CONCRETE PROPERTIES 24
2.7 INFLUENCE OF EXTREME ENVIRONMENT 30
2.8 DISCUSSION 33

v
CHAPTER III METHODOLOGY 35

3.1 MATERIALS 37
3.1.1 Coarse Aggregate 37
3.1.2 Fine Aggregate 38
3.1.3 Ordinary Portland Cement 38
3.1.4 Water Reducing Agent 39
3.1.5 Water 40
3.1.6 Nano Silica 40
3.2 MIX DESIGN OF CONCRETE 41
3.2.1 Experimental Design 41
3.2.2 Mix Design 42
3.2.4 Sample Preparation 43

CHAPTER IV RESULTS AND DISCUSSION 44

4.1 SLUMP, TEMPERATURE, AND WORKABILITY 44

4.2 COMPRESSIVE STRENGTH TESTING 48
4.3 VISUAL ANALYSIS 50
4.4 COST ANALYSIS 51

CHAPTER V CONCLUSION AND RECOMMENDATION 53

5.1 CONCLUSION 53
5.2 RECOMMENDATION 54

REFERENCES 56

vi
 LIST OF TABLES

Table No. Page

2.1 Effect of nanomaterial on mechanical properties 28

3.1 Characteristics of nano-SiO2 41

3.2 Sample mix ratio for 0.001m3 cubes 43

4.1 Slump test and temperature measurement 45

4.2 Average compressive strength results for 7 and 28 days 48

43 Cost effectiveness of Nano Silica for concrete mixes 52

vii
 LIST OF FIGURES

Figure No. Page

1.1 Ancient structure utilizing an early concrete 1

1.2 Flowchart of the experimental process 7

2.1 A study comparing the strengths of concrete made using 11

different cement brands

2.2 Centrepoint loading test 13

2.3 Effect of w/c ratio on flexural strength 13

2.4 Effect of curing conditions on 90-day flexural strength 14

2.5 Tensile Strength Test 15

2.6 Tensile strength relation to temperature 16

2.7 Tensile strength relation to flexural strength, shape, and 16

size of sample

2.8 Heat flow chart on different stages of hydration 19

2.9 Compressive strengths of mix designs with different NS 25

concentration

2.10 Comparative graph on the effect of different nanoparticle 26

contents on tensile and flexural strength

2.11 SEM micrograph of sample without(top) and 27

with(bottom) nanomaterial addition

2.12 Grout of sample without (left) and with (right) 27

nanomaterial addition

2.13 Temperature variance with respect to 1901-2000 average 32

2.14 Cracking and visual effect of high temperature heating 32

2.15 Effect of high temperature on normal concrete, NS, and 33

viii
 NC

3.1 Gantt Chart of FYP A & B 35

3.2 Methodology flowchart of the concrete analysis process 36

3.3 Coarse Aggregates 37

3.4 Sand 38

3.5 Ordinary Portland Cement 39

3.6 Polycarboxylic acid 39

3.7 Ordinary tap water 40

3.8 Powder form of NS 41

3.9 Nano magnetic stirrer 42

4.1 Slump test of control sample 45

4.2 Slump of nano infused sample 46

4.3 Temperature measurement for NS0 47

4.4 Temperature measurement for NS30 47

4.5 Bar chart comparing compressive strength values of each 49

mix

4.6 Physical appearance of control samples 50

4.7 White marks on NS samples 50

ix
 LIST OF ABBREVIATIONS AND SYMBOLS

Symbols
μm Nano meter

A
ACI American Concrete Institute

B
BC Before Christ, the start of Gregorian calendar

C
C Carbon
Ca Calcium
CaCO3 Calcium Carbonate
CO2 Carbon Dioxide
C2S Belite
C3A Aluminate
C3S Alite
C-H Calcium Hydroxide
C-S-H Calcium Silicate Hydrate

D
DOE Department of Engineering
DNA Deoxyribonucleic acid

I
IEA International Energy Agency

K
kWh Kilo watt per hour

x
N
NC Nano Carbonate
NF Nano Ferrite
Nm Nano meter
NS Nano Silica
NSC Composite between Nano Silica and Carbonate
NSX Mix of certain nano silica percentage.
NZ Nano tube

O
O2 Dioxide
OPC Ordinary Portland Cement

S
SEM Scanning Electron Microscope

U
UN United Nations

xi
 CHAPTER I

INTRODUCTION

1.1 BACKGROUND

As defined by Darwin et al. (2016) concrete is a composite material normally

made from cement, stone, sand or gravel, and water. Stone in concrete acts as a coarse
aggregate, whereby it will mix with sand/gravel which acts as a fine aggregate, filling
gaps in between said coarse aggregate and increasing its overall density. Finally, cement
will act as a binding agent which “glues” together each component into concrete. The
origins of concrete as a building material dates way back to 6500 B.C., an invention of
local Bedouin, or Nabatean tribes located in southern Syria and Northern Jordan.

Figure 1 1 Ancient structure utilizing an early concrete (Gromicko and Shepard 2006)

Concrete found its way through various civilizations at different points in time
with each civilization having their own iteration of the material, such as China in 3000
BC, the Greek in 600 BC, and finally the Romans, who had mastered concrete-based

1
construction in 200 BC. However, the modern version of concrete only appeared in
1824 after Joseph Aspdin had invented modern cement by heating a mixture of
limestone and clay at very high temperatures. In the same period, Francois Coignet had
started embedding steel rods within concrete, which became the basis for its usage as a
means of flexural reinforcement. (Gromicko & Shepard, 2006) In the modern world,
concrete has become the most widely used material for construction. It owes its
widespread usage due to its characteristics of being very strong, durable, and versatile
while at the same time being economical. It is owing to these facts that most modern
structures are built using concrete, from residential buildings, infrastructural buildings,
to industrial buildings. However, usage of concrete is not without its drawbacks. For
example, cement production by itself consumes a large amount of energy. From mining,
transport, and processing, cement production for every ton requires 1.758 kWh worth of
energy to make (Babor & Judele, 2009). In addition to this, more effort has been made
globally to push towards better sustainability, which in turn leads to new governmental
regulations worldwide demanding stricter regulations in how projects are managed and
executed as well as the increase in environmental concerns among the public. To top
this off, construction managers must keep their costs in mind, all the while construction
projects are increasing in terms of complexity. (Lynch 2021) Hence, there is a need to
either find an alternative material to replace concrete, or an innovation in the production
process of concrete which can simultaneously promote better sustainability and cost
effectiveness while still maintaining construction quality.

Throughout the years, there have been many attempts to replace concrete with a
more sustainable material. A few examples (Sturla, 2020) of these are as common as
timber and steel, to new innovative materials such as bamboo, timbercrete, or plastic
waste. However, these potential substitutes either still lack the amount of research and
development required for them to be truly applicable or, as they are now, their usage is
still very limited to specific use cases only. On the other hand, there is also the option of
making an innovation for concrete, namely how the mechanical properties of concrete,
such as strength and durability be improved while at the same time reducing its adverse
impact on the environment. One emerging field that aims to tackle this problem is
nanotechnology. As defined by Mansoori & Soelaiman (2005), nanotechnology refers to
the ability to build and work with something at a molecular level (“nano” referring to
objects ranging from 1-100 nanometers in size). Working on such a small scale offers
2
various advantages that relate to the physical properties of matter, as they can allow
humans to modify the very “DNA” of matter, hence improving them to better suit
human usage. For example, usage of nanostructures can increase a matter’s density and
conductivity, thus allowing for the invention of smaller electrical circuits. Another
example is the capability of placing man-made nanomachines inside living cells, in turn
allowing for the creation of new materials based on nature’s self-assembling properties
(National Nanotechnology Initiative, n.d.). To date, some successful applications of
nanotechnology range from material science to energy, such as flexible and bendable
smartphones, better diagnostic tools, increase in the efficiency of fuel production, to
name a few. Knowing this, the application of nanotechnology in the construction
industry will bear a similarly positive impact.

To date, numerous successful experiments have been made on improving

concrete properties using nanomaterials. As previously stated, concrete is made from
fine aggregates, coarse aggregates, water, and cement. Out of these materials, cement is
the only material that is fine enough to allow for the implementation of nanomaterials.
Combined with what is known of nanomaterials’ beneficial properties, the modification
of cement content with nanomaterials was undoubtedly seen as an attractive proposition.
Unsurprisingly, experiments where Portland cement was partially substituted with
nanomaterials such as nano-tubes (CNTs), nano- SiO2 (NS), nano clay (NC), nano-ZnO2
(NZ), and nano-Fe2O3 (NF) bore fruit. With the proper proportions, nano concrete
samples saw increases in its mechanical properties, such as improvements in
compressive strength and flexural strength (Abdalla et al. 2022). Nano concrete also
saw improvements in its porosity, where porosity was reduced due to nanomaterials
providing a pore-filling effect in the micropores within concrete. In addition,
nanomaterials are also environmentally friendlier. Nanomaterials enhance the strength
of concrete greatly, leading to a reduction in the amount of cement needed to reach a
specified strength, which in turn also leads to reduction of costs and CO2 emissions
(from production of cement). Despite this, there are still drawbacks in the
implementation of nanomaterials, such as reduced workability and increased safety risks
because of nanoparticles (Khalid & Taha, 2012). Studies are still inconclusive on the
influence of nanoparticles towards concrete workability, with various studies claiming
they reduce, improve, or have negligible effect on workability. Secondly, adverse health
effects from nanoparticles exposure are another source of major concern, which can
3
occur from its manufacturing process or demolition of nanomaterial-based structures,
both of which are very likely scenarios in the construction industry. Although this
means that engineers and scientists still have a lot of homework to do in making
nanomaterials industry ready, further research and future improvements in technology
will undoubtedly give nanomaterial usage even better prospects.

1.2 PROBLEM STATEMENT

Global environmental crisis continues to rise, along with an increase in

environmental awareness within the general populace and activist groups (Nature 2021).
In response, governments around the world have introduced increasingly stricter
regarding environmental sustainability. At the same time, standards in living and
working spaces are also increasing. Structures are not only becoming architecturally
more complex, but also held to a higher degree of safety and longevity. Should
construction companies continue to adopt the same unsustainable practices as they have
always done, they will eventually suffer from the pushback and inefficiency resulting
from a lack of innovation. (Busta, 2016) Therefore, there is a need for the construction
industry to innovate in how they operate their projects. This research aims to tackle this
problem by introducing a way to produce stronger, more durable, yet environmentally
sounder concrete through the usage of nanomaterials. Nanomaterials, nano-SiO2 or nano
silica has been observed to substantially improve the mechanical properties of concrete
(Abdalla et al. 2022), potentially reducing the need for cement, which in turn will make
projects more cost-effective and environmentally friendly.

4
1.3 SIGNIFICANCE

1. This research aims to act as a reference for the mechanical properties and high-
temperature performance of nanomaterial-modified concrete.
2. Illustrate how usage of nanomaterials in concrete production will result in an
increase in efficiency of concrete usage for engineering applications.
3. Analyze how the hydration mechanism of nanomaterials in turn improves the
mechanical properties of concrete.
4. Compare the effect of nano silica utilization using different percentages in
concrete.

1.4 OBJECTIVES

As a material, Nano-SiO2 greatly influences chemical and hydration reactions of

cement. This research aims to analyze the effect of nano-SiO2 on the mechanical
properties of concrete. Therefore, the objectives of this study are as follows:

1. To investigate the potential impact of nanomaterials in the construction industry in

terms of cost effectiveness and environmental impact.

2. To assess the impact of nanomaterials towards the mechanical properties of

concrete.

3. To find the optimum mixture of nanomaterial inclusion in concrete.

5
1.5 RESEARCH SCOPE

This research aims to test the effect of nanomaterials by comparing the

mechanical properties of concrete infused with varying concentrations of nanomaterials
NS in respect to standard concrete. The nanomaterials used will be nano-SiO2 of size
20nm. The effect of nanomaterials on the hydration process and on the concrete
structure will also be analyzed briefly by slump, temperature, and visual analysis.

6
1.6 METHODOLOGY

Figure 1 2 Flowchart of the experimental process

For this experiment, multiple raw materials for concrete production will be
prepared beforehand, such as cement, coarse aggregates, fine aggregates, and water.
Along with basic concrete materials, nanomaterials used for the nano-concrete specimen
will also be prepared. After which, an inspection will be held to determine the quality
and composition of each material before processing. Next, concrete mix samples with
different nanomaterial concentrations will be prepared, with a separate batch tested for
its 7-day compressive strength. A slump and temperature test will also be done, do
determine changes made by the NS on concrete’s workability and internal reactions.
The rest of the batch will undergo 28 days of curing. Finally, they will also be tested for
their mechanical properties.
7
1.7 ORGANIZATION

This paper will be divided into five chapters. The first chapter will serve as an
introduction to the topic, where the background, problem statement, significance,
objectives, scope, and methodology will be described. The purpose of this first chapter
will be to identify the looming problem that this research aims to solve. The second
chapter will be a comprehensive literature review spanning from the basic
characteristics of concrete, its mechanical properties, its chemical processes, up to
nanotechnology, and finally on nano-modified concrete. It will also cover
environmental concerns arising from the construction industry. Chapter three will cover
the methodology of the experimental process, from the materials used, equipment used,
and mix designs. It will also describe the mixing and preparation process. Chapter four
will specifically discuss the experimental results based on chapter three and connect
them to previous research as described in chapter two. Finally, chapter five will
conclude this paper by summarizing findings made from the experiment, as well as
giving recommendations to future research concerning nano concrete.

8
 CHAPTER II

LITERATURE REVIEW

2.1 INTRODUCTION

Cement-based concrete has long been a staple in construction, due to its high
strength, relatively low costs, and availability. (Amran M, 2022) However, there has
been push for more sustainable practices in construction, despite conflicting interests
with the environmentally demanding industry, resulting in tighter government
regulations, corporate pressure for environmental health, and increased difficulties in
cost management. (Lynch 2021) Additionally, worsening environmental and especially
global climate conditions also play detrimental impact for construction, especially
because of the impact they have towards concrete, such as weakened mechanical
properties and reduced density. (Drzymała et al. 2017) Because of changes in the
climate, temperature increases have continued to grow since the end of the 20 th century,
where further increases are expected in the years to come. (NOAA National Centers for
Environmental Information, 2023) These increases are attributed to the release of
greenhouse gases such as CO2, (Climate.gov, 2023) where the construction industry is
responsible for a staggering 39% of global CO2 emissions. (IEA, 2019) Therefore, an
innovation must be made in the industry, which is capable of simultaneously improving
structural integrity, while at the same time having a positive environmental impact. One
such innovation can come from the implementation of nanomaterials, particularly in the
production process of concrete. Cement production alone allegedly contributes to 8% of
global CO2 (Nature, 2021), whereas cement is required to ensure concrete reaches a
certain desired strength. Nanomaterials, in particular NS reduce the amount of required
cement due to its positive effects on the mechanical properties of concrete, such as its
compressive, tensile, and flexural strength. (Zhuang & Chen, 2019; Ma & Zhu, 2017;
9
Mujkanovic et. al., 2022; Al-Zubaidi et al. 2018; Nigam & Verma, 2023) For this
reason, there is an excellent incentive for further research on nanotechnology
implementation in construction.

This literature review will cover everything from concrete to nanotechnological

science. Starting from concrete and its basic properties, the environmental impact of
construction, an overview of nanotechnology, discussion on the nanomaterials to be
used in this study, a review of experimental results by other researchers on nano-
concrete applications, a review on the effects of worsening climate in concrete and
nano-concrete, microscopic analysis research on nano-concrete, and finally a discussion
on key points in this review.

2.2 MECHANICAL PROPERTIES OF CONCRETE

2.2.1 Compressive Strength

Compressive strength is defined as the maximum amount of load that can be

applied to an object before failure. Compressive strength is the most important property
in structural design as it can give an assessment of a structure’s capability to resist
downward force. It is also capable of determining a concrete specimen’s quality.
(Broughton, 2012) Many factors can affect the performance of concrete in terms of its
compressive strength. First, aggregate type and quality. In a 2020 journal by Rahman,
concrete specimens were made using four different types of fine aggregates, where it
was found that there was a 31% difference in compressive strength between the sample
using the best and worst aggregate type respectively. Secondly, cement quality also
plays an important role in the compressive strength of concrete. Bamigboye et. al.
(2015) discovered a difference of 183% when testing concrete specimens made with

10
different brands of cement. Next, mix design also plays a huge part in affecting
compressive strength in concrete. A study was done using four common methods of mix
design which constitutes the Department of Environment (DoE), American Concrete
Institute (ACI), Road Note 4 (RN4) and CPIIO methods. After a 28-day period, the
CPIIO mix design was noted to be approximately 17% stronger than the lowest
performing mix, the ACI. (Aginam et al. 2013) The fifth factor that affects compressive
strength in concrete is time, where all journals performing concrete-related experiments
have found a linear increase of compressive strength in proportion with curing time.
Generally, concrete will reach 90% of its strength at 14 days, and 99% after 28 days.
Finally, temperature also plays a major part in determining the compressive strength of
concrete. Higher temperatures cause a faster reaction, where concrete specimens can
reach a higher level of strength at earlier stages. However, the faster reaction caused by
a high temperature environment also reduces the final strength of concrete (El-Zohairy
et al. 2020)

Figure 2 1 A study comparing the strengths of concrete made using different cement brands
(Bamigboye, et al.., 2015)

11
2.2.2 Flexural Strength

Flexural strength is the resistance to being broken from bending. It is especially

important for applications such as pavement design, as the load received by a concrete
slab from traffic is akin to a beam under deflection. There are two common methods of
testing flexural strength; the first of which is by center-point loading, and the other by
third point loading. Centrepoint loading (or three-point loading) places one load on mid-
beam while third point loading (or four-point loading) loads the beam at one-third
intervals on the entire beam length. Many factors influence the flexural strength of
material. The first in water-cement ratio, where there is noted to be an optimal amount
of w/c ratio that can be reached before the concrete specimen loses strength. An article
by Shah et al. (2020) found that concrete mixes with 0.3 and 0.4 w/c ratio have lower
flexural strength in comparison to the one with the highest w/c ratio at 0.5, which also
sports the highest flexural strength among the three samples. Meanwhile, another
research found that increasing w/c ratio after a certain point damages the flexural
strength of concrete, where the concrete with lowest w/c ratio at 0.54 boasts the highest
flexural strength in comparison to its peers with a higher w/c ratio. Therefore, the
optimum w/c ratio would range from 0.5 to 0.54. Another factor influencing flexural
strength is curing. In this study by Zhang et al. (2015), six concrete mixes with different
proportions are tested under different curing conditions. In general, it was found that a
cold curing condition provided the best results in terms of flexural strength for the
concrete while a dry condition is very detrimental. Like compressive strength, the age of
concrete also impacts its flexural strength. In this study by Ahmed et al. (2016), four
mixes of different proportions were observed for their compressive and flexural
strength. Across all samples, it was observed that there was an increase of flexural
strength in proportion to their age.

12
 Figure 2 2 Centrepoint loading test (ACPA, 2013)

Figure 2 3 Effect of w/c ratio on flexural strength (Shah et al. 2020)

13
 Figure 2 4 . Effect of curing conditions on 90-day flexural strength (Zhang et al. 2015)

2.2.3 Tensile Strength

Tensile strength is the capability of material to resist breaking through method of

extension. (Chakraborty J. , 2012) Put simply, it is the resistance to not break from
being pulled apart. The most common method to measure this parameter is the splitting
test, where a cylindrical-shaped concrete specimen is put under load on the longitudinal
plane. (Liao et al. 2020) Eventually, a crack will form once enough force is applied
results will be taken, which will be recorded as the sample’s tensile strength. Tensile
strength in concrete is an integral part of structural integrity. Although tensile strength
in concrete is comparatively low to compressive its strength, nevertheless it has
significant bearing on the serviceability and durability of concrete, as issues like
cracking are usually linked to low tensile strength. (FIB, 2010) Like compressive and
flexural strength, there are many factors which influence tensile strength in concrete.
Composition plays a large part in this, from water-cement ratio, aggregate type, and
aggregate size. (Reinhardt, 2013) Curing and moisture plays an important part as well,
as dry concrete experiences shrinkage and cracking, consequently reducing its tensile
strength. (Krausz and Krausz, 1988)

In 1996, Bazant and Kaplan formulated a relationship graph between tensile

strength and temperature. (Bazant and Kaplan, 1996) The diagram showed that although
concrete itself is very resistant to high temperatures, it will inevitably weaken the
14
material due to the incompatibility of the thermal expansion of aggregate and the
cement paste, which weakens the bond and consequently the concrete. Like the
previously discussed compressive and flexural strength values, tensile strength also
benefits from age. (Gutsch, 1988) Time affects the rate of reaction between particles in
the concrete mix, which in turn affects the hardening process of concrete. Next, loading
duration is another factor influencing tensile strength. The rate process theory states that
an external force causes the number of breaking bonds to outnumber recombining
bonds, weakening the material’s strength. Finally, there is specimen size. The size of a
concrete specimen, or in more practical terms the size of a member inversely correlates
with flexural strength. Hillerborg developed a statistical model on the effect of member
size towards its flexural strength. The x-axis represents the dimensions of the beam
against the y-axis, representing the tensile strength. (Hillerborg, 1986)

Figure 2 5 Tensile Strength Test (IS:5816, 1999)

15
 Figure 2 6 Tensile strength relation to temperature (Bazant & Kaplan, 1996)

Figure 2 7 Tensile strength relation to flexural strength, shape, and size of sample (Hillerborg,
1986)

16
2.2.4 Durability

Durability is the capability of a certain material to remain functional during its

intended usage life. In construction, this means that the structure must be in a usable, or
serviceable condition during its design life. As most structures are made using concrete
as primary material, it is important to consider the concrete’s durability into
consideration during design. There are three primary factors that may cause
deterioration in concrete, namely by chemical degradation, thawing, and reinforcement
corrosion. Chemical degradation is further classified into by acids, by salts, expansive
salts, and alkali-silica reactions. When concrete is wet, water seeping in its pores will
start to freeze and expand, causing cracks. A subtype of thaw-based deterioration is
frost-thaw de-icing salt damage. Reinforcement corrosion can be caused by two
mechanisms, which are carbonation and chloride ions. Carbon dioxide from the
atmosphere reacts with calcium hydroxide in the concrete, resulting in the formation of
calcium carbonate. The concrete's alkalinity gradually decreases along with its pH
value, causing the passive layer shielding the steel reinforcement inside the concrete to
break down, meaning carbon dioxide is now free to reach the steel and causing
corrosion. (Bijen, 2000) On the other side, chloride ions penetrate the pores and cracks
of the concrete to reach the steel reinforcement. (Chakraborty et al. 2021) They also
directly break down the protective layer protecting the steel, ultimately causing
corrosion. Left unchecked, these factors can evolve into more pressing issues for
structural integrity, or in other words defects. Defects can come in the form of cracking,
blistering, spalling, curling, efflorescence, and honeycombing, which all imply a
problem within the structure and will ultimately shorten the service life of said structure.
(Sahu, 2022) Knowing this, preventive and restorative methods are required to
minimize the effects of deterioration. For example, chemical degradation can be
defended against by usage of electrolyzed water in the concrete mix; thawing can be
resisted by inclusion of air-entraining agents and increase in density of concrete; steel
corrosion can be prevented by usage of a good concrete cover, cathodic protection, and
various surface treatments. (Patel, 2019)

17
2.3 HYDRATION MECHANISM OF CONCRETE

Cement hydration occurs because of multiple chemical processes that happen

when cement mixes with water. Cement itself is formed by heating limestone and clay
at a very high temperature, after which clinker will be obtained. A small amount of
gypsum is then added to the clinker which functions to control setting time, which
results in cement. The cement hydration process occurs in four stages: consisting of
dissolution, induction, acceleration, followed by deceleration. (Marchon & Flatt, 2016)
In the first stage, alite is dissolved, producing heat followed by a deceleration in the
number of reactions produced. In the next stage, induction, Calcium Silicate Hydrate
gel, or C-S-H is formed. It is very influential on the microstructure of cement, which in
turn affects its mechanical properties. C-S-H gel will continue to form until it reaches a
certain critical size, beginning the acceleration period. The main peak of the heat release
during the acceleration phase correlates to a significant precipitation of CSH and CH
compounds that are responsible for setting and hardening of the cement. After this
phase, the reaction will slow down, marking the deceleration phase. Finally, the cement
enters a steady state where little to no reaction occurs due to the hardened structure of
the cement. Other than the hydration process, it is also important to understand the
factors that are responsible in cement hydration, such as water-cement ratio, admixture
inclusion, cement type, and aggregate type. The importance of the hydration process
comes down to its effect on concrete, where it is responsible in determining the said
concrete’s mechanical properties, such as the influence of C-S-H development on
concrete durability as well as its strength. (Thomas et al. 2009)

18
 Figure 2 8 Heat flow chart on different stages of hydration (Marchon & Flatt, 2016a)

2.4 GLOBAL ENVIRONMENTAL ISSUES

The United Nations defines sustainability as “meeting the needs of the present
without compromising the ability of future generations to meet their own needs”. (UN,
n.d.) Presently, the United Nations projects that the global human population will
increase to 9.8 billion by 2050 and 10.4 billion in 2100. (UN, 2022) Consequently, an
increase in population will necessitate the development of more land to fulfill the needs
of the coming generation. Although this fact means excellent prospects for the
construction industry, environmentally this does not bode quite as well. 20 years since
the start of the 21st century, there was a loss of 100 million hectares of forest area,
because of logging, farming, and agricultural activities. (Weber & Sciubba 2019)
Moreover, construction and developmental processes damage the environment even
further by virtue of the waste produced. It was estimated that 30% of the total weight of
building materials are wasted, where a large portion of these is dumped into landfills. In
2018, the construction industry was found responsible for 36% of energy usage as well

19
as 39% of global CO2 emissions, which is more than any other industry in the world.
(IEA, 2019) Fortunately, there are still practices that can be implemented to remediate
its adverse effects. First is an energy-efficient building design. A study by Pacheco et
al.(2012) recommends that factors such as a building’s orientation, shape, and external
building surface to volume ratio will influence the energy demand greatly. Second,
waste management. There are three key strategies in minimizing waste production from
construction, such as increasing awareness, 3R (reduce, reuse, recycle), and most
importantly empowering government agencies and policies. The government must
incentivize or penalize proper/improper waste management through stronger policy
enforcement. (Saadi et al. 2016) Finally, the usage of more sustainable, alternative
building materials must be pushed. Concrete production is a very emission intensive
process- where 8% of total CO2 emissions are produced by cement manufacture.
Methods to remedy the problem of cement production includes decarbonation through
substitution of fossil fuels, carbon capture, and implementation of alternative cement
materials such as slag, fly ash, and nanomaterial. (Nature, 2021) However,
implementing these practices will not be a smooth process. The process in
implementing more sustainable practices is rife with challenges such as higher
construction costs; increased project complexity; difficult and lengthy bureaucracy; as
well as a lack of knowledge, information, and awareness on sustainable building
processes and materials. (Joshua Ayarkwa, 2022) Ultimately, ensuring that construction
will have a more sustainable future is the responsibility of all stakeholders in society,
and it is not a task that can be solely delegated to construction professionals alone.

2.5 NANOMATERIALS AND NANOTECHNOLOGY

Nanomaterials are simply defined as a material of very small size, ranging from
1 to 100 nanometers in size. Nanotechnology therefore is a method of producing objects
at nanoscale. According to Bayda et al.’s review in 2020, nanotechnology and
nanomaterials have been used since ancient times to craft intricate art and architectural
pieces. However, the introduction of the concept itself was coined by Richard Feynman
20
in 1959 while the term and definition were coined by Norio Taniguchi in 1974, as “the
processing of separation, consolidation, and deformation of materials by one atom or
one molecule”. Later in 1981, the STM microscope was invented, which in turn lead to
the development of the carbon nanotube. There are two main approaches in manufacture
of nanotechnology; the top-down approach involves breaking down matter into smaller
systems such as minerals or silicon into transistors; the bottoms-up approach, where
atoms and molecules can be organized into a larger system and even organisms, such as
living cells into man. (Nouailhat, 2008) In current times, nanotechnology experiences
diverse application in many fields, not limited to: IT, security, medicine, transportation,
and energy. Medicinal applications include better probing, imaging, and the
development of future technology. (Saini et al. 2010)

Despite its potential, there are major concerns regarding the implementation of
nanotechnology. First is its effect on environmental health. Due to their small size,
nanoparticles may be absorbed by living organisms, such as from carbon-based particles
causing respiratory and cardiovascular issues on exposure. Toxicology studies also
show that nanoparticles are toxic towards aquatic microorganisms and animals.
(Taghavi SM, 2013) Second is a lack of public awareness towards the field. To facilitate
the general adoption of any emerging technology will require efforts from stake holding
parties, which in turn is influenced by factors such as public perception. A study
observed that public perception is influenced by various factors, such as fear,
environmental concerns, biases, trust, demographic, and media coverage. (Ankita
Rathore, 2021) For example, media coverage provides laymen with simple facts
regarding the topic of nanotechnology, which may help to de-alienize the concept.
Third, another pressing concern on the development of nanotechnology is nano-divide.
As nanotechnology is considered by some to be the next revolutionary technology,
ethical concerns have been rising regarding the availability of these technologies,
towards poorer, less developed countries, which if not tackled well will drive the gap
between developing and developed countries even further than ever before. (Schroeder,
2016) One critique towards nanotechnology development argues that most
nanotechnology innovations are those aimed for profit, such as cosmetics and sports
equipment, meanwhile only a few products are made to benefit the poor, like water
nano-filters, cheaper drugs, better fertilizers, and lighter-weight construction materials.
21
In this context, Geoffrey Hunt (2006) argued that “can we at last… make an
international cooperative effort to put nano-technological developments at the service of
human and ecological welfare, or will it be primarily nanotechnology for more over-
consumption?”. All in all, efforts to further ethicize nanotechnology must continue to be
made in conjunction with development of new technologies, be it from an
environmental, geopolitical, or social aspect.

2.5.1 Nano SiO2

Silica is a material which is commonly found on the Earth’s surface, in sand and
quartz. (Yadav and Raizaday 2016) It has various applications in the modern world,
ranging from pharmaceutics, food & beverages, and electronics. The application of
silica depends on the type of silicate, which can come as colloidal, fumed, high-purity
ground, gel, or precipitated. (Lindroos et al. 2010) In turn, the resulting silicate depends
on the inherent quality of a silica along with the processing method used. (Bulatovic,
2015) Nano Silica is a derivative of silica, produced from micron-sized silica. Like its
base material, Nano Silica (abbreviated to NS) has widespread applications such as in
medicine and agriculture. In medicine, gold-coated NS was found in the treatment of
tumors and malaria. Meanwhile, NS usage in agriculture was found to be potent soil
stabilizers, pesticide, and in reducing fertilizer costs. (Pooja Goswami, 2022) In
construction, although NS is not yet commonly found, silica fume (a micro silica) has
already been used in manufacture of ultra-high-performance concrete (UHPC) as it was
found to improve its hydration process, mechanical properties, and density. (A. Lazaro,
2016) In addition, NS was also found to improve the workability of concrete when
minimal superplasticizer was included. NS also has self-healing capabilities, reacting
with CH and formulating C-S-H gel. (Kwok Wei Shah, 2020) Unfortunately, safety
hazards have been linked with NS usage. NS dust has been found to cause respiratory
problems and liver injury from continuous inhalation. (Khan, 2018) Therefore, further
research on minimizing this risk as well as clear on-site safety protocols are a must.

22
2.5.2 Nano CaCO3

Calcium carbonate, or CaCO3 , 3is a chemical compound formed from Calcium

(Ca). Carbon (C), and Oxygen (O2). (Omari et al. 2016) Other common names for
CaCO are carbonic acid calcium salt or chalk. Chalk has various applications in pulp
and paper industries, rubber production, construction, pharmaceutics, and cosmetics. In
these applications, they are mostly used as filler material. (Marianne Gilbert, 2017) In
PVC, usage of chalk as filler improves processing, dispersion, and electrical properties,
as well as cost reduction. (Martin-Martinez & Jose, 2002) They can be found naturally
in chalk, limestone, marble, and dolomites. NC is the same material as standard CaCO3 ,
only that its particle size is in the nano range (1-100 nm). Like its base material, NC has
various industrial applications, such as paint, plastics, and adhesives. It owes its
widespread usage to its many advantageous properties, being biocompatible,
biodegradable, while requiring low costs for its synthesis. Production of NC comes from
the synthesis of calcium carbonate’s nanoparticles, where various methods are used.
The most common methods include the carbonation method and the precipitation
method. The carbonation method induces a reaction between calcium hydroxide and
carbon dioxide gas to form calcium carbonate, while the precipitation method involves
the reaction of a calcium salt solution with a carbonate source, such as sodium
carbonate, to form calcium carbonate. (Fadia P, 2021) In concrete production,
implementation of NC can improve many of its properties. NC has been found to
improve concrete’s compressive strength, elastic modulus, reduce its permeability,
improve its microstructure, improve scaling resistance, and minimize cracking by
reducing expansion. (Poudyal L, 2021) On top of this, NC proves to be far safer than
NS, with a study by Amora et al (2020). concluding that the inclusion of NC as
additives has no exposure risk towards environmental and human health.

23
2.6 INFLUENCE OF NANOMATERIAL ON CONCRETE PROPERTIES

The inclusion of nanomaterials in concrete has consistently been found to

produce beneficial effects which improve the quality of the concrete. Numerous
research incorporating nanomaterials such as NC or NS at different dosages into
concrete has been made, with the nano-concrete compared to a control sample of
standard concrete in terms of their mechanical properties, which include compressive,
tensile, and flexural strength tests. The results found in these studies generally varies
due to a difference in approach and methodology taken by each researcher.

For example, Wang et al. (2022) did tests on three nano-concrete samples
containing 2% NC, 2% NS, and 1%NC + 1%NS. It was found that the NS had lowered
the sample’s mechanical strength, but NC had remarkably improved it, while the
composite sample using both nanomaterials, NSC had still improved in their mechanical
properties but was offset by inclusion of the NS. In a review, Zhuang and Chen (2019)
found NS addition to improve the properties of concrete. A concrete sample infused
with 1.5% NS had improved 28-day compressive strength by 17% in contrast with a
control sample of OPC concrete. Maximum flexural strength is achieved with a higher
dosage of NS at 3%. Maximum tensile strength is similarly found to be achieved with
3% NS dosage. Adnan et al. (2022) on the other hand reported that the addition of 4%
NS by weight of concrete yields a better result than with 2% NS, finding an increase of
13.68% in its compressive strength and 12.35% for its flexural strength. It was also
found here that the inclusion of NS in concrete reduces the amount of slump and
consequently the amount of water needed for the mix. Nigam and Verna (2023) tested
seven different concrete samples each of which contained different NS contents varying
from 0% to 3% with a 0.5% increment. It was found that increasing NS contents also
proportionally improved its mechanical properties, approximately gaining an increase of
27.78% in compressive strength, 29.4% in tensile strength, and 29.8% in flexural
strength. It was also found that increment of the NS had also reduced workability and
decreased specimens’ setting times. Al-Zubaidi et al. (2018) found 3% NS content to
show the highest improvement in mechanical properties of the concrete, while 4% was
24
the optimum nano-content for NC, and 3% for the binary mix of NC and NS. NS
inclusion consistently show the highest impact on mechanical properties, with NC
showing a less impactful result and NSC showing a more conservative effect due to the
combined effects of NS and NC.

Figure 2 9 Compressive strengths of mix designs with different NS concentration (Nigam & Verma,
2023)

25
 Figure 2 10 Comparative graph on the effect of different nanoparticle contents on tensile and
flexural strength. Al-Zubaidi et al. (2018)

Similarly, microscopic, and visual changes are also observed due to the
inclusion of nanomaterials. In the first image, the control sample of cement paste
without NS additive is a lot more fractured in terms of appearance, with needle-like
objects being the connection between particles. In the mixture containing NS,
microstructure is noticeably denser and more compact with less voids in between
particles. (Wang B. W., 2008) In figure 14 from another experiment, the test piece with
NS included also similarly show better compactness in comparison to its reference
counterpart. (Jo et al., 2007)

26
 Figure 2 11 SEM micrograph of sample without(top) and with(bottom) nanomaterial addition
(Wang B. W., 2008)

Figure 2 12 Grout of sample without (left) and with (right) nanomaterial addition (Jo et al. 2007)

Common hypotheses explaining this phenomenon is due to the nanomaterials’

high surface area, which is responsible in improving pozzolanic reactions. Pozzolanic
reactions with Ca(OH)2 is found to be responsible in increasing the amount and quality
of C-S-H gels produced by cement hydration as found by Ma et al. (2017). , who found
the a proportional increase in C-S-H and ettringite crystals to the increase of NS. NS in
this context serves as a densifying agent, which fills voids within the concrete.
Consequently, this improved the concrete’s density and microstructure. (Ngo et al.
2020) CaCO3 particles were similarly found to improve the microstructure in concrete
by formation of C-S-H gels, leading to an increase in early compressive strength and
durability. (Nejad et al. 2018) Findings by other researchers are summarised in table
2.1.

27
 Table 2.1 Effect of nanomaterial on mechanical properties

Opt
imu Splittin Flexura
Nano Compressi
Yea m Advan g l
Author mater ve increase Influence factor
r dos ce increas increas
ials (%)
age e (%) e (%)
(%)

NS improves due
to reaction with
CH, resulting in
NS
Compr more CSH gels
3%,
NC, essive, strengthening.
NC
(Al-Zubaidi et. 201 NS, Flexur NC influenced
4%, 47 68.75 63.63
al 2018) 8 NC+ al, hydration,
NS
NS Tensil improving
C
e compressive
3%
strength and
durability.

Decrease of
slump and
Compr
compaction
essive,
(Nigam & factor. Water in
202 NS Flexur
Verma, NS 27.78 29.4 29.8 between NS
3 3 al,
particles
2023) Tensil
enchances
e
workability.

The high surface

Compr area of NS
essive, absorbs more
(Mujkanović et 202 NS
NS Flexur 13.68 - 12.35 water, reducing
al. 2022) 2 4
al, water needed to
slump achieve adequate
workability.

(Abilash et al. 202 NS NS Compr 17 35 40 Pozzolanic

2021) 1 4 essive, reaction occurs
28
 Opt
imu Splittin Flexura
Nano Compressi
Yea m Advan g l
Author mater ve increase Influence factor
r dos ce increas increas
ials (%)
age e (%) e (%)
(%)

from NS and
calcium
Flexur
hydroxide,
al,
increasing the
Tensil
rate and amount
e
of C-S-H gel
formation.

Used within said

range of 3.2 and
1% respectively,
NC
Compr nano-materials
3.2
(Wu, et al., 202 NC, essive, improves density
%, 10 - 20
2021) 1 NS Flexur and homogeneity
NS
al through
1%
improvement of
cement hydration
products.

NC reacts
with concrete
materials,
Compr
resulting in an
essive,
improvement to
(Nejad et al. 201 NC Flexur
NC 57.2 36.9 45.2 its hydration
2018) 8 0.5 al,
products, in turn
Tensil
causing an
e
increase in its
mechanical
properties.

(Wang et al. 202 NS, NS Compr 8.8 4.0 9.3 Nanoparticles

2022) 2 NC, 2.0 essive, improve the
NSC Flexur structure of the
al, concrete by

29
 Opt
imu Splittin Flexura
Nano Compressi
Yea m Advan g l
Author mater ve increase Influence factor
r dos ce increas increas
ials (%)
age e (%) e (%)
(%)

densifying its
Tensil microstructure
e due to its small
size.

Increasing
nanomaterials
over the
Compr
optimum content
(Safaei et al. 202 NC essive,
NC 25 20 - proved
2021) 1 1.5 Tensil
detrimental to
e
concrete’s
mechanical
properties.

NS
inclusion in the
mix tightens the
concrete
(Ngo et al. 202 NS Flexur structure and
NS - - 14.82
2020) 0 1.5 al produces more
gels, which
altogether
strengthens the
concrete.

2.7 INFLUENCE OF EXTREME ENVIRONMENT

Concrete is a non-combustible material, which means the material is a lot more

fire resistant in comparison with other building materials, such as timber or steel.
30
However, there are still detrimental effects to the concrete’s mechanical properties.
Elevated temperatures cause water within concrete to evaporate, causing cracks and
physiochemical changes in concrete. (Arioz, 2007) As concrete temperature increases,
C-S-H decomposes, resulting in loss of strength in concrete. High temperature also
causes reduction in the tensile strength of concrete, where EN 1992-1-2 notes that
tensile strength decreases linearly up until 600C, where the concrete has little to no
tensile strength. (Saad et al. 1996; Xiao, 2004) Similarly, flexural strength of concrete
also decreases in inverse proportion to temperature. (M. Husem, 2006) To date, there
have been exhaustive research on worsening climate conditions. Within just the first
quintile of the 21st century, there was an increase of 1C in global average temperature
compared to 20th century averages. (NOAA National Centers for Environmental
Information, 2023), Given the relationship between temperature and concrete integrity,
it is imperative to limit temperature effects to a minimum and to understand what effects
temperature changes can cause to concrete.

Wu et al. (2019) explored the effect of NS inclusion in high-temperature

environments in carbon fiber reinforced concrete (CFRC). It was found that the NS
inclusion had proven beneficial to concrete properties, where samples with NS, at 2%
shown to suffer the least loss of compressive, tensile, and flexural strength in
comparison with control samples. This is observed to happen due to the deterioration in
C-S-H gels being offset by reactions caused by additional silica inclusion. In another
research, Brzozowski et al. (2022) also found a similar result, with comparisons made to
the concrete containing no NS to the concrete made using 3% NS, which showed the
best results, where flexural strength at 800C increased by 53% and compressive strength
at 800C increased by 18%. Polat et al. (2021) reported a significant difference in
compressive strength of concrete after heating by 750C, where mixes with HN3 and
NS5 showed the highest difference compared to normal concrete.

Microscopic and macroscopic improvements in the NS-infused concrete was

also found compared to the normal concrete. In terms of visual appearance, concrete
containing the optimum concentration of NS (3%) was shown to have less surface
breakage in comparison to the sample without NS inclusion. (Brzozowski et al. 2022)
Cao et al. (2022) investigated the visual aspect of elevated temperatures in (a) control
sample, (b) NS (c) Micro CaCO3. At 500C and 600C, NS and MC provided less
31
cracking compared to the control sample, however at 800C and 1000C, the control
sample had the least number of cracks compared to NS and MC samples. Therefore,
inclusion of nanomaterials in concrete will generally be beneficial on its resistance
against high temperatures up until a certain degree of heating.

Figure 2 13 Temperature variance with respect to 1901-2000 average (NOAA National Centers for
Environmental Information, 2023)

Figure 2 14 Cracking and visual effect of high temperature heating (Brzozowski, et al.., 2022)

32
 Figure 2 15 Effect of high temperature on normal concrete, NS, and NC (Cao et al. 2022)

2.8 DISCUSSION

Based on our research on previous studies and applications of nano-concrete, we

conclude that the inclusion of nanomaterials in concrete has improved the concrete in
engineering applications. In 2.5, various research and studies have proven that
controlled amounts of nanomaterial inclusion in concrete will generally improve its
mechanical properties. (Zhuang & Chen, 2019; Mujkanović et al. 2022; Nigam &
Verma 2023; Al-Zubaidi et al. 2018) In particular, NS inclusion in concrete promotes
the production of more C-S-H gels (Ma & Zhu, 2017), which is largely responsible for
the mechanical properties of concrete and fills micro pores in-between the concrete,
resulting in a denser microstructure (Ngo et al. 2020). The increased production of C-S-
H gels also helps in offsetting the loss of C-S-H when concrete is exposed to high
temperature conditions (Wu L, 2019), meaning that nanoparticles are capable of
safeguarding against the worsening global climate conditions (NOAA National Centers
for Environmental Information, 2023). In conclusion, the role of cement as the primary
source of SiO2 in the hydration process can be replaced with NS, meaning there will be
a lesser need for cement in the concrete mix. This consequently leads to less
environmental impact produced by construction, as cement contributes to much of
carbon dioxide emissions in construction activities. (Nature, 2021) Therefore, from an
33
engineering, economical, and environmental perspective, application of nano materials
in concrete will bring great benefits to the construction industry.

34
 CHAPTER III

METHODOLOGY

3.0 FLOWCHART AND GANTT CHART

Figure 3 1 Gantt Chart of FYP A & B

Figure 3.1 highlights the Gantt charts for FYP A and B. These Gantt charts
highlight the planned schedule for each phase in the writing of this paper.

35
 Figure 3 2 Methodology flowchart of the concrete analysis process

Figure 3.2 presents the experimental methodology for the analysis and mixing of
concrete samples. First, the raw materials will be inspected for quality control purposes,
then the mix design would be made using the DOE method of concrete mix design.
After mix ratios have been determined, a sample batch were mixed to determine if the
mix design and raw materials are up to standard of concrete properties. If they are not,
new raw materials must be selected, or a new mix should be designed. Should they fulfil
the standard, the experimental process will continue with the batching of concrete mixes
with 2.0%, 2.5%, and 3.0% NS replacing the total weight of cement. Next, performance
of the mixes that have been prepared will be tested using the compressive strength test.

36
3.1 MATERIALS

For this experiment, raw materials such as nanomaterials, fine aggregates, coarse
aggregates, and cement were prepared. The preparation process will involve inspection
of technical parameters and quality control, which will be recorded for further
evaluation.

3.1.1 Coarse Aggregate

Maximum size of aggregates used is 20mm, crushed with 1.21% moisture

content and 2.6cm³.

Figure 3 3 Coarse Aggregates

37
3.1.2 Fine Aggregate

The fine aggregate used in the concrete was sand with brownish colour, with
moisture content of 7.7% and 48% passing on 600μm sieve.

Figure 3 4 Sand

3.1.3 Ordinary Portland Cement

The cement class used for the mix was ordinary Portland cement of cement
strength class 42.5N.

38
 Figure 3 5 Ordinary Portland Cement

3.1.4 Water Reducing Agent

A polycarboxylic acid water reducing agent was also used to control the
workability of the concrete mix with a reduction rate of 5%. The brand used is
PENTENS Q – SET.

Figure 3 6 Polycarboxylic acid

39
3.1.5 Water

Ordinary tap water provided by the laboratory facilities was used.

Figure 3 7 Ordinary tap water

3.1.6 Nano Silica

In this experiment, 20 nm NS from Shanghai Yuanjiang Chemical Co., Ltd. is

utilized. It has the appearance of white powder, a particle size of 20 nm, and a content
purity of 99.9%. The dimensions of NS materials are shown in Figure 24, and Table 3.1
provides their physical characteristics. The manufacturer has provided the chemical
characteristics of NS, which are also displayed in table 3.1 below.

40
 Figure 3 8 Powder form of NS

Table 3.1 Characteristics of nano-SiO2

Specific
Particle Purity(% PH Volume Specific Crystal
Item surface area 3
Size(nm) ) value density(g/cm ) gravity(g/cm3) form
(m2/g)

SiO2 20 ≥99.9 5-6 230 0.06 2.2-2.6 Sphere

3.2 MIX DESIGN OF CONCRETE

3.2.1 Experimental Design

The DOE method of concrete design will be used to find the optimal ratio of
cement, water, coarse, and fine aggregates. Then, a portion of the cement will be
replaced using the same amount of NS, where its effect on concrete properties can be
investigated later. Based on the reviewed articles, the optimum amount of NS ranged
from 0.5% to 4%. Based on investigations to previous research and journal articles, part

41
of the cement was replaced by nanoparticles. Experimental preparation will consist of
using cube specimens, where after curing, mechanical properties of the nano concrete
were tested.

3.2.2 Mix Design

The effectiveness of nanoparticles utilization in concrete is highly influenced by

their dispersion, as nanoparticles tend to agglomerate, which leads to uneven dispersion
of particles and consequently weak areas in the mix. Therefore, proper mixing method
is required to ensure that the nano concrete will reach the desired result. Two of the
most used methods include mixing nanomaterials with cement, then adding water and
aggregates and, to first dissolve the nanomaterials in water, then adding cement and
aggregates (Xu et al., 2021). The second method is judged as more efficient in
dispersing NS particles, therefore the second method was used in the dispersion process,
where a stirrer was used to dissolve the NS particles in water before addition to the
concrete mix.

42
 Figure 3 9 Nano magnetic stirrer

The stirring will be done using a nano-magnetic stirrer for a period of 5 minutes.
During this time, the NS will be pre-mixed with water and stirred. While stirring, water
reducing agent is slowly added into the nano solution. Finally, the nano-solution was
put together into the concrete mixer with other raw materials, such as aggregates and
ordinary Portland cement. This experiment used the DOE method of mix design
standard, with a target strength of C25. Mix proportion and amount for each material is
shown in the table 3.2 for one cube sample of volume 0.001 m3. The quantity of NS
used was 2%, 2.5%, and 3% by weight of the cement respectively. For reference, the
control sample uses a ratio of 1:0.54:1.72:2.48, for cement, water, fine, and coarse
aggregates respectively.

Table 3.2 Sample mix ratio for 0.001m3 cubes

Nano-
Water(kg Fine Course Water reducing
Sample Cement(kg) SiO₂(kg
) aggregate(kg) aggregate(kg) agent(kg)
)

Control 0.41667 0.225 0.716817 1.031517 0.00417 0

NS20 0.408337 0.225 0.716817 1.031517 0.00408 0.00833

43
 NS25 0.40625 0.225 0.716817 1.031517 0.00406 0.01016

NS30 0.404167 0.225 0.716817 1.031517 0.00404 0.0125

3.2.4 Sample Preparation

Using the concrete mix design detailed in 3.2.3, each batch will be poured into a
plastic cube mold with dimensions of 100mm*100mm*100mm. Before pouring
however, the mix will be tested for its slump and temperature values. After
approximately one day, the concrete sample will be removed from its mould. Then,
curing will be done for 7 days and 28 days respectively. A total of 24 cubic samples
were made. After 28 days, the 28-day specimens would be taken out of the curing box
to be left to dry. After curing, compression test will be done to test the performance of
the concrete.

CHAPTER IV

RESULTS AND DISCUSSION

4.1 SLUMP, TEMPERATURE, AND WORKABILITY

Immediately after mixing, concrete samples were immediately subjected to

slump tests. This is done to determine the mix design’s suitability in terms of practical
usage, where the average slump for concrete used on beams and columns are at 60-
180mm. Secondly, the slump test is also important in determining the effects of nano

44
inclusion on the workability of concrete, where previous studies indicated that the water
absorbing properties of nanomaterials may reduce concrete workability by a significant
degree. (Nigam & Verma, 2023; Kwok Wei Shah, 2020; Mujkanovic et al., 2022). Low
workability may mean that the mix design, or even inclusion of nanomaterial itself is
impractical for industrial applications. As such, workability is also considered an
important factor in determining the optimum ratio of NS usage in concrete mixes,
regardless of its performance in terms of strength. Slump test is done using the standard
cone test, where a cone is filled to its brim with the concrete mix, whereafter the cone is
lifted to measure the height difference between the cone (the initial height of the slump)
vs the final height, this difference would be taken as the slump. Another measurement
taken was on temperature, which was taken immediately after mixing to determine any
increases in temperature due to the presence of Silica from NS triggering additional
chemical reactions. (Ma & Zhu, 2017) Table 4.1 as well as figures 4.1 and 4.2 shows
the result of these tests.

Table 4 1 Slump test and temperature measurement results

Temperatur
Slump e
Mix (mm) (C˚)
NS0 96 29
NS20 39 29.7
NS25 33 30.4
NS30 25 29.7

45
 Figure 4 1 Slump test of control sample

Figure 4 2 Slump of nano infused sample

Based on table 4.1, the design mix itself had achieved the target slump value at
60-180mm, where the achieved result is at 96 mm, which indicates it has sufficient
workability. However, subsequent tests with NS infused samples had shown a very

46
significant drop in terms of workability. Gathering from these results, NS is clearly
responsible for a reduction in the workability of concrete, as previous studies have
shown. A prevailing theory as to why this happens may be due to the high surface area
of NS particles, a trait which encourages higher water absorption (Mujkanovic et al.,
2022) and resulting in a much drier concrete. For the temperature, only negligible
changes in the mix temperature are observed, however the slight improvement in
temperature of NS samples can indicate a faster reaction within the structure of the
concrete mix (Ma & Zhu, 2017), consequently leading to a slightly faster setting time as
result of NS.

Figure 4 3 Temperature measurement for NS0

47
 Figure 4 4 Temperature measurement for NS30

4.2 COMPRESSIVE STRENGTH TESTING

As has been elaborated in 2.2.1, compressive strength is the most important

parameter in construction. This is because most of the load received by structural
members in a project is mostly compressive because of gravity. As such, compressive
strength testing is done to determine the overall performance of concrete mixes to know
whether the design measures up to standards/requirements prescribed by the structural
designer. The mechanical properties of each mix design are tested by compressive
strength test, giving data in the table 4 2 below.

Table 4 2 Average compressive strength results for 7 and 28 days

Average comp. Strength

Mix 7day 28day
48
 NS0 21.18 24.033
NS20 20.34 28.867
NS25 19.927 26.903
NS30 24.553 32.303

For each mix design, 3 samples were made and tested, from which the average
value of compressive strength is taken. Based on the 7-day results, compressive strength
test results indicate a change of -5.78%, -5.916%, and 15.925% respectively for 2.0%
nano, 2.5% nano, and 3% nano admixtures. Based on the 28-day curing results,
compressive strength results show a change of 20.09%, 11.93%, 34.41% for each NS-
based design respectively. The 7-day results for NS20 and NS25 samples shows a slight
reduction in compressive strength as opposed to the NS0 sample, while the NS30
sample enjoyed a quite significant improvement in compressive strength. For the 28-day
results, the compressive strength of all nano samples had shown improvement unlike the
7-day results.

A common trend between 7- and 28-day samples is that the NS30 mix had
shown the highest amount of improvement in performance, which is followed by the
NS20 mix, and finally the NS25 mix. NS30 had shown the most significant
improvement in performance but also the lowest amount of slump, indicating a lower
moisture content because of the absorption process from the NS inclusion. (Mujkanovic
et al., 2022) The downwards trend in slump value further supports this hypothesis, as
slump values seem to consistently go downwards with each addition in NS. The results
for NS30’s compressive strength followed by a huge drop in slump value also increases
in inverse proportion with the improvement of compressive strength. To conclude, the
optimum admixture of NS was 3% based on the replaced quantity of cement, albeit this
comes at the cost of greatly reducing workability of the material. This also implies that a
reduction in cement to achieve a certain target strength is viable, seeing as the
introduction of small amounts of NS is capable of significantly improving the
mechanical properties of concrete. However, the inclusion of additional water or the

49
exclusion of water reducing admixtures should be considered to minimize the impact of
NS.

Comparison between compressive strength of each

mix
35

30

25

20

15

10

0
NS0 NS20 NS25 NS30

7day 28day

Figure 4 5 Bar chart comparing compressive strength values of each mix.

4.3 VISUAL ANALYSIS

Based on visual inspection, there are some white marks shown on the surface of
the NS doped samples as shown in figure 4 7, this contrasts with control samples shown
on figure 4 6, which is relatively unblemished. Though the initial hypothesis as to why
this happened was due to agglomeration of NS as highlighted by Xu et al. (2021),
however it does not seem to impact the mix other than visually.

50
 Figure 4 6 Physical appearance of control samples

Figure 4 7 White marks on NS samples

4.4 COST ANALYSIS

In addition to the parameters previously discussed, another important aspect is

cost. Cost is equally an important parameter in the construction as costs often determine
the viability of a method. Therefore, analysing the cost needed to implement NS usage
into construction projects is vital.

51
 In chapter 3, materials used for the experiment are listed as follows; water,
cement, fine aggregate, coarse aggregate, water-reducing admixture, and finally Nano
Silica. Table 4.2 elaborates and compares the material cost of concrete for each design
mix, based on their compressive strength with respect to its price. Pricing for each
material shown is based on retailer prices in Malaysia, except for NS prices which is
taken from a Chinese manufacturer. Another assumption taken in determining the
pricing is that they are to be purchased in bulk, at least 1 ton in weight for each material
used. The metric used to measure and compare the cost-effectiveness of each mix
design is by dividing the total price for an assumed one-meter cube worth of concrete by
their 28-day compressive strength test results. The resulting value would be in terms of
money spent, in RM for each unit of strength, in MPa or N/mm2. Results from this
analysis shows that inclusion of NS has generally improved the cost effectiveness of the
mix, especially the higher the amount of NS used, where NS3 has improved cost
effectiveness of concrete by 23.337% as opposed to the NS0 sample. However, it is to
be noted that since bulk prices generally tend to be cheaper than retail, NS will not be
very cost effective should only small quantities are utilized. Therefore, NS usage might
be more suitable for medium or larger scale projects in opposed to smaller ones in terms
of its applicability for industry purposes.

Table 4 3 Cost effectiveness of Nano Silica for concrete mixes

Price / m3 of concrete
Material NS0 NS20 NS25 NS3
286.726 286.726 286.726 286.726
Sand 7 7 7 7
Coarse aggr. 928.368 928.368 928.368 928.368
250.000 245.000 243.750 242.500
Cement 2 2 2 2
94.2500 114.867 141.375
NS 0 8 3 1

Water 0.36 0.36 0.36 0.36

52
 18.3750 18.2812 18.1875
Admixture 18.7515 1 6 1
1484.20 1592.35 1617.51
Total (RM) 6 1573.08 3 8
28-day comp strength 24.03 28.85 26.9 32.3
61.7647 54.5261 59.1952 50.0779
RM/N/mm2 3 7 9 4

CHAPTER V

53
 CONCLUSION AND RECOMMENDATION

5.1 CONCLUSION

This report aims to study the effect of NS inclusion in concrete, replacing a set
amount of cement with NS which substitutes the silica content in cement with that of
pure NS. Cubic samples were to utilize to compare and analyse factors such as
performance, workability, hydration, and cost analysis respectively. Experimental
results find that:

- Inclusion of NS has proven beneficial to the performance of concrete; however,

it comes at the cost of losing workability. This problem can be resolved by
inclusion of more water in the mix, however that in turn will come at the cost of
noticeably lower compressive strength. Therefore, further research on reducing
the detrimental effects of NS on workability needs to be done, such as by
inclusion of workability improving admixtures.
- Another consideration that can be taken to improve NS-based concrete
workability is the inclusion of additional water and exclusion of accelerating
admixtures. Though this will come at the cost of losing some strength and a
longer setting time for concrete.
- Basing results on performance alone, inclusion of 3% NS per weight of cement
is the optimum value for the mechanical properties of concrete,
- At 3%, there was an increase of compressive strength by 33.34% in comparison
to the control sample, followed by a decrease of 74% in slump during slump
tests.
- Based on visual inspection, inclusion of NS seems to result in white stains on the
NS specimens.
- Cost analysis results shows that higher NS usage increased the cost effectiveness
of the concrete, as for a relatively low cost the concrete achieves a higher

54
 improvement in strength. This means that to achieve a certain target amount of
compressive strength, less cement is required. Consequently, reducing cement
usage will greatly benefit the environment.
- Concerning the use of NS in an industrial setting, it is very cost ineffective for
smaller projects, as purchasing it in smaller volumes or at retail value leads to an
astronomical increase of project costs. Therefore, further research on mass-
producing NS cheaply should be pursued, and industrial stakeholders having an
interest in NS for their projects are better reserving it for larger projects.
- In addition, NS as a material is dangerous when handled improperly, Industrial
usage of NS therefore should also put safety precautions into deep consideration,
especially during the mixing process.
- Finally, further research needs to be done to standardize the usage of NS. As of
now, quantifying the effectiveness of NS usage is not possible without direct
testing. Therefore, mix design methods such as DOE or ACI should also take NS
into consideration, or a new system focusing on NS concrete should be
developed.

5.2 RECOMMENDATION

The following are recommendations made for future research of NS:

- Safety must be always kept in mind, NS is hazardous and lightweight material,

meaning slight gusts of wind from natural sources of air conditioning devices
can easily scatter its particles and potentially endanger many. Therefore, it is
highly recommended to handle NS in an enclosed space with the proper
protective equipment, such as face masks, gloves, and safety goggles.
- Other than mix design, the consistency of each material must be kept. For each
mix, each material used in the experiment must be used in the exact condition in
parameters such as water content, purity, and particle size.

55
- It is also recommended to batch a larger number of samples together at once, to
take less days for testing purposes. Planning batch, curing, and testing dates is
also recommended.

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