International Journal of Pavement Engineering
ISSN: 1029-8436 (Print) 1477-268X (Online) Journal homepage: https://www.tandfonline.com/loi/gpav20
State-of-the-art report on use of nano-materials in
concrete
Md. Safiuddin, Marcelo Gonzalez, Jingwen Cao & Susan L. Tighe
To cite this article: Md. Safiuddin, Marcelo Gonzalez, Jingwen Cao & Susan L. Tighe (2014)
State-of-the-art report on use of nano-materials in concrete, International Journal of Pavement
Engineering, 15:10, 940-949, DOI: 10.1080/10298436.2014.893327
To link to this article: https://doi.org/10.1080/10298436.2014.893327
Published online: 14 Mar 2014.
Submit your article to this journal
Article views: 967
View related articles
View Crossmark data
Citing articles: 28 View citing articles
Full Terms & Conditions of access and use can be found at
https://www.tandfonline.com/action/journalInformation?journalCode=gpav20
International Journal of Pavement Engineering, 2014
Vol. 15, No. 10, 940–949, http://dx.doi.org/10.1080/10298436.2014.893327
State-of-the-art report on use of nano-materials in concrete
Md. Safiuddina*, Marcelo Gonzalezb, Jingwen Caob and Susan L. Tigheb
a
School of Architectural Studies and Angelo Del Zotto School of Construction Management, George Brown College, 160 Kendal Avenue,
Toronto, Ontario, Canada M5T 2T9; bCentre for Pavement and Transportation Technology (CPATT), Department of Civil and
Environmental Engineering, University of Waterloo, 200 University Avenue West, Waterloo, Ontario, Canada N2L 3G1
(Received 8 November 2013; accepted 7 December 2013)
Nanotechnology application to concrete presents an innovative approach to improve concrete properties based on the ability
to manipulate the cementitious material at an atomic scale. This paper presents a review of the nano-materials that have been
used in concrete. The literature survey revealed that four nano-materials are most often used to modify concrete properties;
these include nano-silica (nano-SiO2), nano-titanium dioxide (nano-TiO2), carbon nano-tubes (CNTs) and carbon nanofibres (CNFs). All of these four nano-materials have shown improvement in many concrete properties. Both nano-TiO2 and
nano-SiO2 reduce bleeding and segregation, and improve mechanical and transport properties. CNFs and CNTs tend to
adversely affect the fresh properties due to agglomerations, which are overcome when a surfactant or ultrasonic mixer is
used. However, both CNFs and CNTs significantly improve the mechanical properties of concrete. This paper also discusses
how concrete durability is improved when nano-materials are added to concrete. In addition, this paper identifies several
research needs based on the gaps in the current state of knowledge on using nano-materials in concrete.
Keywords: concrete properties; durability; nanotechnology; nano-materials; nano-concrete
1.
Introduction
According to the Cement Association of Canada (CAC),
2.7 billion tons of cement was manufactured in the world
to produce 9 billion cubic meters of concrete during
2007 (CAC 2013). Concrete is the most widely used
material in the world due to its versatility, durability and
sustainability. With the correct design and construction
process, users can obtain a service life of concrete over
50 years.
Regarding the constituent materials of concrete, the
Strategic Development Council from the USA states that
there exists a variety of research needs to improve ‘energy
efficiency, productivity, and the performance of concrete
and concrete products’ (Strategic Development Council
2002). These research needs may be categorised in three
groups: new materials, measurement and prediction, and
reuse and recycling. Nano-materials can be considered in
the group of new materials.
The applicability of nanotechnology in a variety of
fields is receiving additional attention (Gopalakrishnan
et al. 2011). Nanotechnology involves manipulating
matter and materials at scales below 100 nm. It is a
revolutionary tool that allows us to take advantage of the
radically different material properties that appear on the
nano-scale (WIN 2012). Nano-scale is the boundary
between atoms and molecules. The fundamental behavior
and associated properties of materials are dictated at the
atomic scale (Ashby et al. 2009). Therefore, a reduction in
*Corresponding author. Email: safiq@yahoo.com
q 2014 Taylor & Francis
the particle size to nano-scale associated with high surface
area can produce a significant impact on material
properties.
In recent years, more interest is growing on the use of
nano-materials in concrete. The literature survey reveals
that most of the studies conducted to date have focused on
the use of nano-silica (nano-SiO2) (Shih et al. 2006,
Quercia and Brouwers 2010, Said et al. 2012), nanotitanium dioxide (nano-TiO2) (Diamanti et al. 2008, Chen
et al. 2012, Jalal et al. 2012), carbon nano-tubes (CNTs)
(Li et al. 2007a, 2007b, Mudimela et al. 2009) and carbon
nano-fibres (CNFs) (Toutanji et al. 1994, Mudimela et al.
2009) in concrete. In comparison, limited research
has been carried out to investigate the prospect of using
nano-iron (nano-Fe2O3), nano-alumina (nano-Al2O3),
nano-zirconium dioxide (nano-ZrO2), nano-lotus leaf,
nano-slag, nano-fly ash, nano-cellulose and nano-clays.
This paper presents an extensive review on the use of
nano-materials in concrete. The key aspects of nanoconcrete, the use of different nano-materials, and the
effects of the major nano-materials on the properties and
durability of concrete are discussed in this paper.
2. Nano-materials and nano-concrete
The application of nanotechnology in concrete is still in its
infancy, but it has been recognised that nano-particles can
be used to produce nano-concrete with enhanced concrete
International Journal of Pavement Engineering
941
Figure 1. Specific surface area of different constituent materials used in conventional concrete, high-strength/high-performance
concrete and nano-concrete. Source: Adapted from Ashby et al. (2009).
performance (Ashby et al. 2009). According to research in
recent years, nano-concrete is defined as a concrete made by
Portland cement and cementitious particles with sizes
smaller than 500 nm (Balaguru and Chong 2008, Sanchez
and Sobolev 2010). The important reasons to apply
nanotechnology on concrete are to control material behavior,
achieve superior mechanical and durability performance, and
to provide novel properties in concrete such as low electrical
resistivity, self-sensing capability, self-cleaning and selfhealing abilities, high ductility and self-control of cracks
(Sanchez and Sobolev 2010). Because of the high surface
area to volume ratio, nano-particles can act as nuclei for
cement phases, providing excellent chemical reactivity to
promote cement hydration. Figure 1 shows the range of
specific surface area for different materials used in concrete.
This figure also provides the definition of nano-concrete
(nano-engineered concrete) (Ashby et al. 2009).
Concrete undergoes different phases during hydration
where nano-materials can play a significant role. The
different hydration characteristics of concrete are presented
in Table 1. Calcium silicate hydrate (C–S–H) is the main
product from the hydration process and presents a poorly
Table 1.
crystalline or amorphous structure (Bensted and Barnes
2002). It is well known that C–S–H gel controls the
strength and durability of concrete (Skinner et al. 2010). At
this time, no consensus exists regarding the atomic structure
of C–S–H and how C–S–H is able to develop strength.
Tylor (1997) described a model to characterise the atomic
structure of C–S–H based on X-ray diffraction and
scanning electron microscope (SEM) testing. The research
reported that C–S–H has an amorphous composition and
its nano-structure coincides with the 1.4 nm tobermorite
layer structure. Moreover, according to Skinner et al.
(2010), C–S–H can be characterised by a nanocrystalline
structure, represented closely by 1.1 nm tobermorite.
Nanotechnology allows us to improve the understanding of the C–S–H atomic structure. According to
Skinner et al. (2010), this new knowledge permits scientists
to manipulate the C –S–H structure and therefore design
concrete with enhanced properties. Based on nanotechnology, Selvam et al. (2009) explained that electrostatic forces
and bond forces in the silicate chains are mainly responsible
for strength development in the C–S–H atomic structure.
Therefore, nanotechnology can play a significant role in
Hydration characteristics of Portland cement concrete (w/c ¼ 0.5).
Physical/chemical component
Approximate
volume (%)
C– S– H
50
Calcium hydroxide (CH)
Ettringite and monosulphate phases (AFm and AFt phases)
Unreacted cement particles
Capillary pores
12
13
5
20
Source: Adapted from Bensted and Barnes (2002).
Comments
Includes gel pores; poorly crystalline/amorphous
structure
Crystalline structure
Crystalline structure
Based on the hydration process
Dependant of w/c
942
Md. Safiuddin et al.
explaining the mechanisms of cement hydration in
concrete. Furthermore, nanotechnology may contribute to
sustainable development. It has been reported that the
manufacturing of 1 ton of Portland cement produces about
1.0–0.8 ton of CO2 that causes adverse effect on the
environment (Skinner et al. 2010). Enhancement of
concrete properties and durability would compensate this
adverse effect and thus the use of nano-concrete could be a
strong motivation towards environmental sustainability.
3.
Different types of nano-materials for concrete
The literature survey revealed that mostly four nanomaterials, namely nano-SiO2, nano-TiO2, CNTs and
CNFs, have been used in concrete.
3.1
in a wide range of applications such as paints, cosmetics
and drugs because of its low toxicity, semi-conductivity,
high chemical stability, availability and low industrial
cost (Hamdy and Ion 2011). TiO2 can also be supplied as
nano-TiO2, which is most widely used as a photo-catalyst
due to its extraordinary photo-catalytic activity (Chen et al.
2012). It has also been used in concrete (Diamanti et al.
2008, Chen et al. 2012, Jalal et al. 2012).
Nano-silica
Nano-SiO2 is a widely used nanomaterial in concrete. The
main chemical component of nano-SiO2 is silicon dioxide
(SiO2); it can be present in crystalline and amorphous
forms. The amorphous nano-SiO2 is most commonly used
in nano-concrete (Quercia et al. 2012). Nano-SiO2 presents
sphere morphology and its particles size is variable.
According to Quercia and Brouwers (2010), the particle size
varied in the range of 5–658 nm in six different nano-SiO2
products. Nano-SiO2 is available in powder and slurry forms.
The slurry form is attractive in order to avoid health problems
associated with ingesting the powder. Figure 2 presents an
SEM image of a commercially available nano-SiO2, where
the sphere morphology is very clear.
3.2 Nano-titanium dioxide
Titanium dioxide (TiO2) is the naturally occurring oxide of
titanium. In nature, it is present in the following minerals:
rutile, anatase and brookite. TiO2 has historically been used
Figure 2.
Transmission electron micrographs of nano-SiO2.
3.3
Carbon nano-tubes
CNTs were discovered in Japan by Sumio Ijima during
transmission electron microscopy observation in 1991
(Ashby et al. 2009). The discovery was accidental while an
electrical discharge occurred between two carbon electrodes. CNTs can be defined as cylindrical molecules with a
nano diameter (1 nm to a few nanometers) and a length
lower than few micrometers. CNTs are made of carbon
atoms interconnected together by carbonZcarbon (CZC)
bonds (Rashid 2012). Based on the manufacturing
conditions, CNTs can be generated as single-walled,
double-walled or multi-walled. The hexagonal structure of
the carbon lattice in the CNTs provides a very strong
structure. The morphology of single-walled CNT
(SWCNT) and multi-walled CNT (MWCNT) is presented
in Figure 3. MWCNTs are less expensive and more readily
available than SWCNTs (NRCC 2013).
CNTs exhibit several key engineering properties
including very high Young’s modulus of 1000 GPa,
high tensile strength of 30 GPa, superior current density
of 109 A/cm2 and high thermal conductivity of 6000 W/mK
(Ashby et al. 2009). CNTs possess better material
properties than CNFs and according to the National
Research Council of Canada (NRCC), they are ideal
reinforcing materials for concrete (NRCC 2013).
International Journal of Pavement Engineering
943
4. Effects of nano-materials on different
properties of concrete
Based on the literature review, nano-materials influence
both the fresh and hardened properties of concrete. The
effect of nano-materials on the fresh properties, cement
hydration, microstructure, pore-structure, mechanical
properties, transport properties and durability of concrete
has been summarised in the following sub-sections.
4.1
Figure 3. Single-walled and multi-walled CNTs. Source:
Adapted from Rashid (2012).
3.4
Carbon nano-fibres
CNFs play a very significant role in cement concrete
because of its extraordinary and useful properties, such as
exceptional tensile strength, high stiffness, low density,
good chemical stability, and high electrical and thermal
conductivity (Zhang et al. 2007, Mudimela et al. 2009).
CNFs have cylindrical nanostructures with diameters less
than 100 nm. Also, Tyson et al. (2011) reported that CNFs
possess a Young’s modulus of 400 GPa and a tensile
strength of 7 GPa. According to Gay and Sanchez (2010),
CNFs have a lower production cost than CNTs and
therefore their use in concrete could be cost-effective.
The improvement in the engineering properties of nanoconcrete cannot be guaranteed based only on the excellent
material properties of CNFs and CNTs. This is because the
properties of these nano-materials are influenced by two
other important factors; firstly, the nano-filaments must be
dispersed in the paste matrix and secondly, the bond
strength between the matrix and surface of CNFs or CNTs
must be achieved. The proper dispersion of CNFs (Figure 4)
can be achieved in nano-concrete or nano-composite by
engineering the mixing process.
Effects on fresh concrete properties
The fresh properties of concrete are affected by the particle
size distribution of constituent materials. Therefore, nanomaterials are expected to influence the fresh concrete
properties due to their extremely small particle sizes. The
research findings of Quercia and Brouwers (2010) and
Gonzalez et al. (2013) showed that nano-SiO2 significantly
reduces the workability of concrete for given water content
due to high specific surface area. A similar effect was also
observed in the case of nano-TiO2 (Chen et al. 2012).
This suggests that the water demand is strongly related
with the specific surface area of nano-materials. Quercia
and Brouwers (2010) stated that a higher amount of water
is needed for a constant workability when the surface area
of nano-SiO2 is increased. Therefore, high-range water
reducing admixture or superplasticiser is required to
maintain the target workability of concrete (Gonzalez
et al. 2013) when the water content is kept unchanged, as
obvious from Figure 5. The air-void stability of concrete is
also affected in the presence of nano-SiO2. Hence, a higher
dosage of air-entraining admixture is needed for a given air
content of concrete (Gonzalez et al. 2013), as can be seen
from Figure 5. It should also be mentioned that the demand
for both high-range water reducing admixture and airentraining admixture increased linearly with the higher
percentage of nano-SiO2 in concrete. This is evident from
Figure 5. Moreover, because nano-SiO2 produces higher
7000
Dosage (ml/m3)
6000
CNF
AEA
HRWRA
5000
4000
3000
2000
1000
0
CC (0.0%Nanosilica) NSC 1 (0.5%
Nanosilica)
NSC 2 (1.0%
Nanosilica)
NSC 3 (1.5%
Nanosilica)
Type of concrete
CNFs in cement paste matrix
Figure 4. Scanning electron micrograph of CNF-composite.
Source: Adapted from Gay and Sanchez (2010).
Figure 5. Air-entraining admixture (AEA) and high-range water
reducing admixture (HRWRA) demands for nano-concrete with
different nano-SiO2 contents. CC: conventional concrete; NSC:
nano-silica concrete. Source: Adapted from Gonzalez et al. (2013).
944
Md. Safiuddin et al.
plasticity than traditional cementitious materials, it can
improve the cohesiveness of the concrete and thus reduce
the bleeding and segregation (Quercia and Brouwers 2010).
Nano-materials can significantly influence the rheology
and stability of concrete. According to Jalal et al. (2012),
nano-TiO2 is able to modify the rheological properties of
self-compacting concrete. The rheological properties were
studied through slump flow, V-funnel flow and L-box tests.
Nano-TiO2 powder improved the consistency and homogeneity of the fresh concrete mixture, with less bleeding and
segregation. This can be explained by the fact that nano-TiO2
acts as a filler in the mixture and improves the resistance to
water movement in fresh concrete.
Certain nano-materials might influence the setting of
concrete. For example, the higher nano-TiO2 content and
fineness decrease the setting time of concrete. This is
related to acceleration of the hydration process and
associated heat release. Hydration heat peak increases
when the nano-TiO2 is added into the cement. The particle
fineness and specific surface area play a dominant role in
enhancing the dissolution rate of cement compounds at the
early stage of cement hydration, thus increasing heat
release (Chen et al. 2012).
Nano-materials may cause adverse effects on the fresh
properties of concrete if they are not dispersed properly.
More specifically, dispersion issues with CNFs and CNTs
were reported by several authors (Gay and Sanchez 2010,
NRCC 2013, Rashid 2012). Overall, it is difficult to
achieve homogeneous dispersion of CNTs and CNFs in
concrete mixture (Nasibulina et al. 2010). These nanomaterials are prone to affect the fresh concrete properties
due to agglomerations. The attraction between particles of
CNFs/CNTs due to Van der Waals forces might be
responsible for agglomerations. However, the use of a
surfactant or ultrasonic mixer allows for adequate
dispersion. Also, the use of high-range water reducing
admixture was successful in disaggregating the CNFs, thus
improving the dispersion of nano-fibres in the cement
matrix (Gay and Sanchez 2010).
4.2
Effects on cement hydration
The incorporation of nano-materials such as nano-SiO2,
CNTs and nano-TiO2 can positively influence the
hydration reactions and the physical structure of C –S – H
in cement (He and Shi 2008, NRCC 2013, Chen et al.
2012). Using a field emission scanning electron microscope (FESEM), He and Shi (2008) explained that nanoSiO2 not only makes a dense material but also can change
the morphology of hydrated cement by producing more
C – S– H gel and less ettringite crystals. According to
Ashby et al. (2009), the drastic increase in surface area of
nano-SiO2 can affect the surface energy, morphology and
the chemical reactions in concrete. The high specific
surface area of nano-SiO2 compared with other concrete
materials has been shown in Figure 1. Because of low
particle size and high surface fineness, nano-SiO2
contributes to the creation of small-size crystal and
clusters of C – S –H during pozzolanic reaction.
Like nano-SiO2, adequately dispersed SWCNT can
also accelerate the hydration process in cement paste
(NRCC 2013). This is possibly due to SWCNTs appearing
to act as nuclei for C3S (tricalcium silicate) hydration
reaction, with the C – S – H forming directly on the
SWCNT. Moreover, SWCNTs produce an increase in
the maximum heat flow. This may also enhance the
hydration of cement in concrete. Furthermore, the
incorporation of nano-TiO2 in powder form can significantly accelerate the rate and degree of hydration at early
stages; it can promote the formation and precipitation of
hydration products (Chen et al. 2012).
4.3 Effects on microstructure and pore-structure of
concrete
Nanoparticles can potentially allow better void filling and
other positive filler effects due to the extremely low
particle size in comparison with conventional cementing
materials of concrete (Ashby et al. 2009); the filler effects
produce a concrete microstructure with improved density
and reduced porosity (Sanchez and Sobolev 2010).
According to Ashby et al. (2009), nanoparticles organised
themselves in an efficient close-packed configuration. In
geometry, close-packing of similar spheres is a dense
arrangement of congruent spheres in an infinite and regular
arrangement. He and Shi (2008) explained that nanomaterials can act as fillers creating a dense and less permeable
mortar microstructure; also they may act as nuclei to
facilitate the creation of hydration products and thus may
promote the formation of high-density C –S – H structures.
Hosseini et al. (2011), Said et al. (2012) and Ji (2005)
observed such effects in the case of nano-SiO2. Ji (2005)
showed the improvement of microstructure of concrete
including nano-SiO2 based on the field emission scanning
electron microscope (FESEM) test. It was concluded that
the addition of nano-SiO2 can make the microstructure of
concrete more uniform and compact than normal cement.
In 2010, Hosseini et al. (2010) carried out an experimental
study to explain the modification of concrete microstructure in the presence of nano-SiO2. They summarised that
nano-SiO2 contributes to improve concrete microstructure
in four ways: (a) acting as a nucleus, (b) generating better
C –S – H, (c) controlled crystallisation and (d) filling of
micro-voids.
The replacement of a certain amount of cement with
nano-SiO2 decreases the porosity of concrete (Mondal
et al. 2010, Shirgir et al. 2011, Said et al. 2012). The
concrete mixtures with nano-SiO2 have less threshold pore
diameter than the control mixtures without nano-SiO2 (Lin
et al. 2008a, 2008b, Said et al. 2012). Also, nano-SiO2
International Journal of Pavement Engineering
results in a better pore structure refinement in concrete
(Said et al. 2012).
The porosity of concrete is also decreased when nanoTiO2 is used with cement. Nano-TiO2 can modify the pore
size distribution and decrease the total pore volume by
filling up the pore space around them gradually as
hydration continues (Chen et al. 2012). Zhang and Li
(2011) and Ali and Shadi (2011) found that the pore
structure of concrete containing nano-TiO2 is finer than
that containing nano-SiO2. Therefore, the concrete
containing nano-TiO2 can exhibit a higher resistance to
the penetration of deleterious agents than the concrete
containing nano-SiO2.
4.4
Effects on mechanical properties of concrete
Nano-materials improve the mechanical properties of
concrete due to improved particle packing and better
bonding. According to Quercia and Brouwers (2010), the
properties of hardened concrete are governed by the
overall grading of the solid materials. The increase in the
particle size range including very small solid particles with
dimensions below 300 nm improves particle packing.
Based on the analysis of six commercial nano-SiO2
products, Quercia and Brouwers (2010) reported that
nano-SiO2 is a suitable alternative to improve grading
since its particle size ranges from 5 to 658 nm. In addition,
nano-materials result in an improvement in aggregate/
paste contact zone, thus producing a better interfacial bond
between aggregate and cement paste (Gopalakrishnan
et al. 2011).
Several studies indicated that the addition of nanoSiO2 in cement paste can improve the compressive
strength of concrete due to its high surface area and
pozzolanic effect (Ji 2005, Shih et al. 2006, Flores et al.
2010, Said et al. 2012, Gonzalez et al. 2013), as evident
from Figure 6. It is already recognised from the past
research that silica fume (micro-silica) can result in a
higher strength in concrete (Mondal et al. 2010). Due to
more particle and surface fineness, nano-SiO2 is more
effective than microsilica to increase the compressive
strength. Furthermore, the addition of nano-TiO2 up to
3 wt% can significantly increase the compressive strength
of concrete by forming a larger amount of hydration
products (Ali and Shadi 2011, Chen et al. 2012).
Not only compressive strength, nano-materials can
also improve the flexural strength of concrete. Gopalakrishnan et al. (2011) reported that nano-SiO2 increases
both the compressive and flexural strengths of concrete.
Similar results were also observed by Hosseini et al.
(2010) as shown in Figure 7. The other nano-materials
such as nano-TiO2 and CNFs also significantly improve
the compressive and flexural strengths of concrete (Li et al.
2004, 2006, Metaxa et al. 2010).
Metaxa et al. (2010) tested the flexural strength of the
concrete samples reinforced with 0.025%, 0.048%, 0.08%
and 1% CNFs by weight of cement. They concluded that
the optimal content of CNFs is 0.048 wt%, which provides
the strength increase up to 45%. Also, they mentioned that
CNFs ensure the full capacity of the fibres to transfer the
load due to excellent bonding between the nano-fibres and
the cement hydration products. Furthermore, the test
results from Zhou et al. (2009) showed that the Young’s
modulus of CNFs and the tensile strength can reach up to
600 MPa and 60 GPa, respectively. According to the report
of Li et al. (2005), the addition of CNTs can also increase
the flexural and compressive strengths of concrete. This
improvement is related to the modification of the concrete
microstructure from three aspects: (a) CNTs interact with
hydrates to produce a high bonding strength and increase
the load transfer capacity, (b) CNTs reduce the total pore
volume in bulk cement paste, thus increasing the strength
of concrete and (c) CNTs treated with H2SO4 and HNO3
mixture solution act as the bridge connection between
cracks and voids (Figure 8) to enhance the tension load
8
100
90
7 Days
80
28 Days
7
Flexural strength (MPa)
Compressive strength (MPa)
945
70
60
50
40
30
20
6
5
4
3
2
1
10
0
0
CC(0.0%
Nanosilica)
NSC1(0.5%
Nanosilica)
NSC2(1.0%
Nanosilica)
NSC3(1.5%
Nanosilica)
Type of concrete
Figure 6. Compressive strength for different concretes
including nano-SiO2. CC: conventional concrete; NSC: nanosilica concrete. Source: Adapted from Gonzalez et al. (2013).
CC (0%Nanosilica)
NSC 1 (1%
Nanosilica)
NSC 2 (2%
Nanosilica)
NSC 3 (3%
Nanosilica)
Type of concrete
Figure 7. Flexural strength of nano-SiO2 concrete. CC:
conventional concrete; NSC: nano-silica concrete. Source:
Adapted from Hosseini et al. (2010).
946
Md. Safiuddin et al.
Figure 8. Scanning electron micrograph of cracked CNTcomposite. Source: Adapted from Sanchez and Sobolev (2010).
transfer, thereby improving the flexural strength of
concrete.
Some nano-materials can significantly improve the
toughness of concrete along with other properties. Rashid
(2012) state that the ultimate strain capacity increases by
142%, the flexural strength increases by 79% and the
fracture toughness increases by 242% when a small
amount of CNT (0.1%) is incorporated into concrete.
These results show that CNTs produce significant
enhancement in the mechanical properties of concrete.
Nano-materials can also improve some of the other
properties of concrete. Li et al. (2006) reported that nanoTiO2 significantly enhances the flexural fatigue performance of concrete. In their study, the concrete with 1% nanoTiO2 by weight of binder exhibited the best flexural fatigue
performance. In this case, the fatigue life was increased by
475.38% and 267.22% at the stress levels of 0.85 and 0.70,
respectively (the stress level was defined by the quotient
between flexural fatigue strength and flexural strength).
4.5 Effects on transport properties and durability of
concrete
Durability is the goal of any agency to ensure a sustainable
development of concrete infrastructure. Mondal et al.
(2010) found that the addition of certain nano-materials
such as nano-SiO2 can significantly improve the durability
of concrete. Calcium hydroxide crystals remain in the
pores of concrete when pH . 12.5 (Mondal et al. 2010). If
the environmental condition lowers the pH, the equilibrium will be disturbed, and it will cause leaching of Ca
(OH)2 from the concrete. The leaching of Ca(OH)2 makes
concrete microstructure porous and thus affects its
durability. The concrete durability is improved with the
reduction in calcium leaching. From the magic angle
spinning-nuclear magnetic resonance spectra of the
cement pastes with nano-SiO2, it was observed that
nano-SiO2 can increase the amount and strength of highstiffness C –S – H (Mondal et al. 2010). The high-stiffness
C – S– H provides a higher resistance to calcium leaching,
which means that the incorporation of nano-SiO2 can
effectively decrease the degradation rate to improve
concrete durability (Gaitero et al. 2008).
The incorporation of nano-materials such as nanoFe2O3, nano-Al2O3, nano-TiO2, nano-SiO2 and nano-clays
(montmorilonite) improves the chloride penetration
resistance of the mortar phase of concrete (He and Shi
2008). Particularly, a small amount of nano-SiO2 and
nano-clays significantly enhanced the chloride penetration
resistance. A similar finding was obtained from other
research: according to Shekari and Razzaghi (2011), a
constant amount (1.5 wt% of cement) of nano-ZrO2, nanoFe2O4, nano-TiO2 and nano-Al2O3 showed a reduction of
chloride penetration in the range of 20 –80%. Moreover,
Said et al. (2012) reported that the rapid chloride
permeability significantly decreased when nano-SiO2
was added into the concrete mixtures. They concluded
that a small amount of nano-SiO2 can provide a significant
effect on reducing the penetration of chloride ions into
concrete.
Nano-materials can substantially decrease the water
permeability of concrete. It has been reported that nanoSiO2 reduces the water permeability because it improves
the microstructure of concrete with compact pore-structure
(Ji 2005, Shirgir et al. 2011, Said et al. 2012). The water
permeability of matured concrete is also reduced due to the
excellent packing condition of nano-TiO2, which can
provide a better compacted and refined pore structure
(Jalal 2012).
A recent study has also shown that the water
absorption decreases when nano-materials such as nanoSiO2 are used in concrete (Jalal and Noorzad 2012). The
authors reported that an addition of 2% nano-SiO2
results in a reduction of 58% and 54% capillary water
absorption at the age of 3 days for the binder content of
400 and 500 kg/m3, respectively. It has been summarised
that the concrete containing nano-SiO2 possesses a more
packed microstructure, and thus exhibits less capillary
absorption (Jalal and Noorzad 2012). Nano-TiO2 also
greatly decreases the water absorption of concrete
(Jalal 2012).
Nano-materials improve the abrasion resistance of
concrete. Abrasion is a definite distress on concrete surface
that may affect floors, pavements and hydraulic structures
(CAC 2012). Therefore a concrete with high abrasion
resistance is desirable. According to Gopalakrishnan et al.
(2011), nano-materials can enhance the abrasion resistance
of concrete. Abrasion resistance is substantially improved
when nano-materials are added to concrete, as obvious
from Figure 9. This figure shows the abrasion resistance
index which is defined by the quotient between the square
root of the head revolutions and the depth of abrasion
grooves. The abrasion resistance of concrete can be
increased by up to 157% when 1% nano-SiO2 by weight of
cement is used in concrete mixture. The abrasion
International Journal of Pavement Engineering
Nano-material is indeed a valuable technology that can
be very useful for many kinds of application. However,
there still exist several implications that must be
considered to enhance the use of nano-materials. These
are related to the prospects of nano-materials and the risks
associated with their use in concrete (Ashby et al. 2009).
In concrete material applications, construction procedures
can adapt techniques to minimise or eliminate health risks
(Birgisson et al. 2010).
3.0
Index of abrasion resistance
947
2.5
2.0
1.5
1.0
0.5
0.0
Conventional concrete
Nano-silica concrete
Nano-titanium concrete
Type of concrete
7.
Figure 9. Abrasion resistance for different nano-concretes.
Source: Adapted from Gopalakrishnan et al. (2011).
resistance of concrete can be increased by 180.7% when
1% nano-TiO2 by weight of cement is used.
Research needs
Significant gaps in the current state of knowledge have
been found from the literature survey on the use of nanomaterials in concrete. The following research needs have
been identified based on the present study:
. Substantial research has been carried out using
5.
Cost-effectiveness of nano-materials
The construction industry is sensitive to the direct cost of
construction. Currently, the use of nano-materials is costprohibitive because of the high initial cost. However, more
demand will reduce the cost of nano-materials (Ashby
et al. 2009). In addition, the project cost must be evaluated
based on the life-cycle assessment since nano-materials
would increase the durability of concrete structures. This
means less maintenance cost and less materials usage
because of a reduction in the maintenance/rehabilitation
interventions. Hence, the use of nano-materials can be
cost-effective in the long run, despite the high initial cost.
6.
Health risks of using nano-materials in concrete
Nanotechnology has the potential for innovations in
construction industry. However, there are reasonable
apprehensions that nano-materials could cause health
damages if not used cautiously (Ashby et al. 2009). Since
nano-material consists of ultrafine particles with nanoscale dimensions (# 100 nm), there are health risks due to
the possible inhalation of nano-particles. Napierska et al.
(2010) reported that ultrafine particles (, 0.1 mm) have
been revealed to cause dangerous inflammatory reactions
and lung damages, even more than fine particles of less
than 2.5 mm size. Due to very small particle size, nanoparticles have the ability to increase the cell penetration,
thus they are more likely to promote biological effects.
Several adverse health effects, such as lung cancer,
silicosis, chronic obstructive pulmonary disease are
mainly related to crystalline silica (for example, quartz
and cristobalite). Amorphous silica such as diatomaceous
earth is considered less detrimental to health (Napierska
et al. 2010). Nano-SiO2 that has been used significantly in
producing nano-concrete contains an amorphous structure.
nano-SiO2 in concrete. The researchers emphasised
the effect of nano-SiO2 on a number of fresh
properties, hardened properties and durability of
concrete. However, limited studies examined the
effect of nano-SiO2 on the air content, shrinkage and
skid resistance of concrete. Also, it is still not clear
whether pozzolanic effect or high specific area of
nano-SiO2 is the main reason for improvement of
compressive strength in nano-silica concrete. More
studies are needed to answer this question.
. Significant interest has grown on the potential use of
CNTs and CNFs because of their excellent
engineering properties and self-healing effect on
nano-cracks in concrete. Most of the studies showed
that it can improve the strength and durabilityrelated (transport) properties of concrete. But fewer
studies research their effects on fresh properties and
durability performance (freeze – thaw resistance,
resistance to sulfate attack, resistance to alkaliaggregate reaction, etc.).
. Some studies have already been done regarding the
effects of nano-TiO2 on the fresh properties,
porosity, permeability, hydration, compressive
strength and fatigue performance of concrete. Yet,
more studies are required to investigate the effect of
nano-TiO2 on the shrinkage, skid resistance and
durability of concrete.
. There are some other nano-materials such as nanoFe2O3, nano-Al2O3, nano-ZrO2, nano-montmorillonite, nano-cellulose and nano-lotus leaf that can be
used in concrete. However, only a few studies have
been carried out to utilise these nano-materials in
concrete. More research should be carried out to
examine the potential effects of these nano-materials.
. In terms of concrete durability in cold regions, the
resistance to freezing and thawing must be evaluated
because there is limited information on the freeze –
948
Md. Safiuddin et al.
thaw performance of nano-materials. In addition, the
effects of nano-materials on the resistance to alkaliaggregate reactions and sulfate attack have not been
investigated.
. Most studies evaluated the performance of nanomaterials based on laboratory results. It is necessary
to verify the field performance in real projects in
order to obtain experience regarding the application
of nano-materials on a larger scale and in different
environmental conditions in terms of temperature,
wind and relative moisture.
. Based on the field experiences, standards, specifications and quality control procedures must be
developed in order to achieve correct application of
nanotechnology. The specifications must include at
least control of the material properties (such as
particle size) and the material dispersion in the
concrete mixture.
. The cost effectiveness of nano-materials based on the
life-cycle cost analysis of concrete structures must be
evaluated to enhance their use in concrete. At present,
it is not clear whether the high initial cost can be
offset by improved concrete performance.
8. Concluding remarks
The application of nanotechnology in concrete materials is
still in its infancy and the potential to advance this state-ofthe-art technology is promising. However, there is still a
gap between research at laboratory scale and field
engineering applications. The literature review revealed
that it is necessary to carry out follow-up research and to
evaluate the field performance of nano-concrete, particularly in cold climate applications.
Nano-materials are useful for concrete in many
applications. Despite some adverse effects on fresh concrete
properties, nano-materials improve the hardened properties
and durability of concrete. Therefore, nano-materials have
a very good prospect in construction industry.
The cost-effectiveness of nano-materials must be
investigated to enhance their use in concrete. Despite the
high initial cost, the use of nano-materials can still potentially
be cost-effective due to improved concrete durability.
The health risks of nano-materials must also be
examined. To enhance the use of nano-materials in
concrete, possible health problems must be avoided at all
times due to inhalation of the materials.
Research on the use of nano-materials in concrete is
ongoing. Several research needs have been identified in
this paper. Future research should focus these areas to
accelerate the use of nano-materials in concrete.
Acknowledgements
The authors acknowledge the support and contribution of the
Natural Sciences and Engineering Research Council of Canada
(NSERC) and the Cement Association of Canada (CAC),
particularly Rico Fung who is the Director of CAC’s Markets and
Technical Affairs in Ontario. The authors are also thankful to
Gloria Stephens, Physiotherapist from South Metropolitan Area
Public Health Care Service (Health Ministry of Chile) for her
advice about health risks of using nano-materials.
References
Ali, N. and Shadi, R., 2011. TiO2 nanoparticles’ effects on
properties of concrete using ground granulated blast furnace
slag as binder. Science China, 54 (11), 3109– 3118.
Ashby, M., Ferreira, P., and Schodek, D., 2009. Nanomaterials,
nanotechnologies and design: an introduction for engineers
and architects. Boston, MA: Elsevier Science Ltd.
Balaguru, P. and Chong, K., 2008. Nanotechnology and concrete:
research opportunities. In: Nanotechnology of concrete:
recent developments and future perspectives (ACI SP-254).
Detroit, MI: American Concrete Institute.
Bensted, J. and Barnes, P., 2002. Structure and performance of
cements. 2nd ed. London, UK: Spon Press.
Birgisson, B., Taylor, P., Armaghani, J., and Shah, P.S., 2010.
American road map for research for nanotechnology-based
concrete material. Transportation Research Record: Journal
of the Transportation Research Board, 2142, 130–137.
Cement Association of Canada (CAC), 2012. Design and control
of concrete mixtures. 8th Canadian ed. Ottawa: Cement
Association of Canada.
Cement Association of Canada (CAC), 2013. Available from:
www.cement.ca [Accessed 25 March 2013].
Chen, J., Kou, S., and Poon, C., 2012. Hydration and properties of
nano-TiO2 blended cement composites. Cement & Concrete
Composites, 34, 642– 649.
Diamanti, M.V., Ormellese, M., and Pedeferri, M., 2008.
Characterization of photocatalytic and superhydrophilic
properties of mortars containing titanium dioxide. Cement
and Concrete Research, 38, 1349– 1353.
Flores, I., et al., 2010. Performance of cement system with nanoSiO2 particles produced by using the sol-gel method.
Transportation Research Record: Journal of the Transportation Research Board, 2141, 10 – 14.
Gaitero, J.J., Campillo, I., and Guerrero, A., 2008. Reduction of
the calcium leaching rate of cement paste by addition of
silica nanoparticles. Cement and Concrete Research, 38,
1112– 1118.
Gay, C. and Sanchez, F., 2010. Performance of carbon
nanofiber – cement composites with a high-range water
reducer. Transportation Research Record: Journal of the
Transportation Research Board, 2142, 109– 113.
Gonzalez, M., Safiuddin, Md., Cao, J., and Tighe, S., 2013.
Sound absorption and friction responses of nano-concrete for
rigid pavements. In: Proceedings of TRB 2013 annual
meeting. Washington, DC: Transportation Research Board.
Gopalakrishnan, K., Birgisson, B., Taylor, P., and Attoh-Okine,
N., 2011. Nanotechnology in civil infrastructure: a paradigm
shift. Berlin-Heidelberg: Springer-Verlag.
Hamdy, A. and Ion, T., 2011. Nanocoatings and ultra-thin films:
technologies and applications. Cambridge, UK: Woodhead
Publishing Limited.
He, X. and Shi, X., 2008. Chloride permeability and
microstructure of Portland cement mortars incorporating
nanomaterials. Transportation Research Record: Journal of
the Transportation Research Board, 2070, 13 –21.
Hosseini, P., Booshehrian, A., and Farshchi, S., 2010. Influence
of nano-SiO2 addition on microstructure and mechanical
International Journal of Pavement Engineering
properties of cement mortars for ferrocement. Transportation
Research Record: Journal of the Transportation Research
Board, 2141, 15 – 20.
Hosseini, P., Booshehrian, A., and Madari, A., 2011. Developing
concrete recycling strategies by utilization of nano-SiO2
particles. Waste and Biomass Valorization, 2, 347– 355.
Jalal, M., 2012. Durability enhancement of concrete by
incorporating titanium dioxide nanopowder into binder.
Journal of American Science, 8 (4), 289– 294.
Jalal, M. and Noorzad, A., 2012. Effect of binder content,
pozzolanic admixtures and SiO2 nanoparticles on thermal
properties and capillary water absorption of high performance concrete. Journal of American Science, 8 (7), 395–399.
Jalal, M., Ramezanianpour, A.A., and Pool, M.K., 2012. Effects
of titanium dioxide nanopowder on rheological properties
of self compacting concrete. Journal of American Science,
8 (4), 285– 288.
Ji, T., 2005. Preliminary study on the water permeability and
microstructure of concrete incorporating nano-SiO2. Cement
and Concrete Research, 35, 1943– 1947.
Li, G.Y., Wang, P.M., and Zhao, X., 2005. Mechanical behavior
and microstructure of cement composites incorporating
surface-treated multi-walled carbon nanotubes. Carbon,
43 (6), 1239– 1245.
Li, G.Y., Wang, P.M., and Zhao, X., 2007a. Pressure-sensitive
properties and microstructure of carbon nanotube reinforced
cement composites. Cement & Concrete Composites, 29,
377– 382.
Li, H., Xiao, H., and Ou, J., 2004. A study on mechanical
and pressure-sensitive properties of cement mortar with
nanophase materials. Cement and Concrete Research, 34,
435– 438.
Li, H., Zhang, M., and Ou, J., 2007b. Flexural fatigue
performance of concrete containing nano-particles for
pavement. International Journal of Fatigue, 29 (7),
1292– 1301.
Li, Z., et al., 2006. Investigations on the preparation and
mechanical properties of the nano-alumina reinforced
cement composite. Materials Letters, 60, 356– 359.
Lin, D.F., et al., 2008a. Improvements of nano-SiO2 on sludge/fly
ash mortar. Waste Management, 28, 1081– 1087.
Lin, K.L., et al., 2008b. Effects of nano-SiO2 and different ash
particle sizes on sludge ash – cement mortar. Journal of
Environmental Management, 88, 708– 714.
Metaxa, Z.S., Konsta-Gdoutos, M.S., and Shah, S.P., 2010.
Carbon nanofiber – reinforced cement-based materials.
Transportation Research Record: Journal of the Transportation Research Board, 2142, 114– 118.
Mondal, P., Shah, S.P., Marks, L.D., and Gaitero, J.J., 2010.
Comparative study of the effects of microsilica and
nanosilica in concrete. Transportation Research Record:
Journal of the Transportation Research Board, 2141, 6 – 9.
Mudimela, P.R., et al., 2009. Synthesis of carbon nanotubes and
nanofibers on silica and cement matrix materials. Journal of
Nanomaterials, 2009, Article ID 526128, 4 pp.
Napierska, D., et al., 2010. The nanosilica hazard: another
variable entity. Particle and Fibre Toxicology, 7, 32 p.
Nasibulina, L.I., et al., 2010. Direct synthesis of carbon
nanofibers on cement particles. Transportation Research
Record: Journal of the Transportation Research Board, 2142,
96 – 101.
National Research Council of Canada (NRCC), 2013. The effect
of SWCNT and other nanomaterials on cement hydration and
949
reinforcement. NRCC Research Report 53569. Available
from: http://www.nrc-cnrc.gc.ca [Accessed 04 April 2013].
Quercia, G. and Brouwers, H.J.H., 2010. Application of
nano-silica (nS) in concrete mixtures. In: Proceedings of
the 8th fib PhD symposium. Lyngby, Denmark: Kgs.
Quercia, G., Husken, G., and Brouwers, H.J.H., 2012. Water
demand of amorphous nano silica and its impact on the
workability of cement paste. Cement and Concrete Research,
42, 344– 357.
Rashid, K.A.A., 2012. Nanotechnology-based system for damageresistant concrete pavements. Texas: Zachry Department of
Civil Engineering, Texas A&M University. Research Report
No. SWUTC/12/476660-00017-1.
Said, A.M., Zeidan, M.S., Bassuoni, M.T., and Tian, Y., 2012.
Properties of concrete incorporating nano-silica. Construction and Building Materials, 36, 838– 844.
Sanchez, F. and Sobolev, K., 2010. Nanotechnology in concrete
– a review. Construction and Building Materials, 24,
2060– 2071.
Selvam, R.P., Subramani, V.J., Murray, S., and Hall, K., 2009.
Potential application of nanotechnology on cement based
materials. Fayetteville: University of Arkansas, Research
Report No. MBTC DOT 2095/3004.
Shekari, A.H. and Razzaghi, M.S., 2011. Influence of particles on
durability and mechanical properties of high performance
concrete. Procedia Engineering, 14, 3036– 3041.
Shih, J., Chang, T., and Hsiao, T., 2006. Effect of nanosilica on
characterization of Portland cement composite. Materials
Science and Engineering A, 424, 266– 274.
Shirgir, B., Hassani, A., and Khodadadi, A., 2011. Experimental
study on permeability and mechanical properties of
nanomodified porous concrete. Transportation Research
Record: Journal of the Transportation Research Board, 2240,
30 – 35.
Skinner, L.B., et al., 2010, 195502 Nanostructure of calcium
silicate hydrates in cements. Physical Review Letters, 104,
1 – 4.
Strategic Development Council, 2002. Roadmap 2030: The U.S.
concrete industry technology roadmap, version 1.0. Detroit,
MI: American Concrete Institute.
Toutanji, H.A., E1-Korchi, T., and Katz, R.N., 1994. Strength
and reliability of carbon – fiber– reinforced cement composites. Cement & Concrete Composites, 16, 15 – 21.
Tylor, H.F.W., 1997. Cement chemistry. 2nd ed. London, UK:
Thomas Telford Ltd.
Tyson, B.M., Abu Al-Rub, R.K., Yazdanbakhsh, A., and Grasley,
Z., 2011. Carbon nanotubes and carbon nanofibers for
enhancing the mechanical properties of nanocomposite
cementitious materials. Journal of Materials in Civil
Engineering, 23 (7), 1028– 1035.
Waterloo Institute for Nanotechnology (WIN), 2012. Available
from:
http://uwaterloo.ca/institute-nanotechnology
[Accessed 02 January 2013].
Zhang, M. and Li, H., 2011. Pore structure and chloride
permeability of concrete containing nano-particles for
pavement. Construction and Building Materials, 25,
608– 616.
Zhang, X., et al., 2007. Ultrastrong, stiff, and lightweight
carbon–nanotube fibers. Advanced Material, 19, 4198–4201.
Zhou, Z.P., et al., 2009. Development of carbon nanofibers from
aligned electrospun polyacrylonitrile nanofiber bundles and
characterization of their microstructural, electrical, and
mechanical properties. Polymer, 50, 2999– 3006.