1.

INTRODUCTION
Till this day, ordinary Portland cement (OPC) retains its popularity as the construction
material of choice in the field of civil engineering. The global production of cement has exceeded
3.6 billion tonnes in meeting mankind’s thirst for urbanization that involves construction of
buildings and infrastructure, especially in fast developing countries such as China and India.
Cement is the principal binder holding the aggregates together to produce concrete in the presence
of water for hydration. As an engineered material, concrete composites are desired for their
excellent compressive strength. However, the major disadvantage of concrete is its brittle nature
which is attributed to its poor resistance to crack formation, low tensile strength and strain
capacities. Depending on the mix proportions of aggregates, cement and water, the tensile strength
of concrete lies in the range of 2–8 Mpa. The improvement in the durability performance of
concrete has been widely accepted by the community as a means to reduce the life-cycle cost of
an infrastructure especially in the maintenance during its service life.
The rapid progress towards construction calls for high performance and smart cementitious
materials to build safer, more durable and more economical infrastructure systems. Compared
with the conventional concrete, high performance concrete requires the concrete with considerably
improved performances such as high strength, high durability, high chloride ion migration
resistivity, high freeze resistance, high sulphate resistance, low shrinkage, low abrasion and low
carbon footprint etc. Among many strategies and concepts improving the concrete performance
and smartness, the idea using additives to reinforce cement paste as well as to tailor its physical,
mechanical and transport properties has been widely explored and investigated. The primary
objectives underneath this reinforcement strategy are (1) to utilize the unique properties of the
selected additives and (2) to minimize the deleterious influences of the per-existing flaws and
micro cracks in concrete, which are an inherent byproduct of cement hydration and usually range
from Nano-scale to meso scale in concrete. During the initial exploration, fiber additives including
steel fiber, carbon fiber and polymer fiber have been used to reinforce cement paste due to their
positive effects on the tensile strength and fracture resistance of concrete. However, since the size
of these conventional fibers is usually at or beyond millimeter scale, their effects on cement paste
are inherently limited at macro and meso scales. To overcome this obstacle, Nano-sized additives
have been attracting increasing attentions during the last decade.

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 In recent years, there has been rising interest in the use of Nano particles in building
materials to enhance mechanical performances and to create multi functional capabilities. These
Nano particles can fill the voids in the cement paste, leading to lower porosity and higher strength.
It is found that after proper treatment, these nanomaterial’s can significantly improve the micro
structure strength of hydration gels. In addition, by enhancing the packing density of calcium-
silica-hydrate (C-S-H), some Nano-sized additives can effectively reduce the micro structure
porosity, and thus greatly decelerate the transport rate of the deleterious agents in concrete.
Therefore, despite certain challenges existing in dispersion, bonding and cost, incorporation of
Nano-sized additives in concrete is showing great potentials for producing stronger and more
durable construction materials. New carbon materials such as carbon fibers, carbon nanotubes and
carbon black were used to enhance the strength of cement composites or provide the cement
composites with improved electric or thermal performance. Nevertheless, the reinforcing materials
such as carbon fibers and carbon Nano tubes only play a physical role in the cement composites,
which does not participate in the hydration and micro structure modification of the cement,
especially the pore structure and crystalline structure of cement paste. And the dispersion of carbon
fibers and carbon nanotubes in the cement matrix is also challenging because of the hydrophobic
surface of these reinforcing materials. Therefore, it is urgent to find a new material which can not
only disperse uniformly in the aqueous system of hydrated cement, but also improve the toughness
of hardened cement paste by micro structure modifications.

Recent advance in materials science and Nanotechnology provides excellent Nano

materials, namely graphene oxide, to be considered as a Nano-sized additive for cementitious
materials. Compared with other nanomaterials, graphene displays a unique atom-thick sp2 bonded
2D structure. Hinging on this atomistic structure, graphene exhibits many extraordinary properties
highlighted by its super-high specific surface area, ultrahigh tensile strength and elastic modulus,
and excellent thermal, electrical and optical conductivity. Therefore, using it to produce smart and
high performance materials garners increasing interests in a wide variety of engineering
applications. Graphene oxide Nano platelets (GO`s) are new types of Nano-particles consisting of
graphene stacks. Different from pristine graphene, GO`s are oxides of GNP's, and thus contain the
functional groups attained during oxidation and exfoliation process. GO`s exhibit a 2D sheet-like
structure with a thickness at Nano-scale (less than 10 nm).Unlike 0D nanoparticles, 1D fibers and
2D sheets behave as reinforcing materials to bridge cracks. GO`s inherit many advantages of

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graphene and make themselves promising nano-sized additives and ideal reinforcement for high
performance and smart structural materials. Furthermore, among the nanomaterials used as
additives in many engineering applications, they are low-cost nano particles. GO`s can bring
smartness to cementitious materials. GO's can be used to quantify the damage extent in concrete
by measuring the electric potential of specimens. GO`s display good dispersion ability in water,
and thus avoid entanglement and agglomeration in large-scale structural application, which is a
perplexing challenge to the nano fiber like additives. graphene oxide (GO) is a layered
nanomaterials consisting of hydrophilic oxygenated graphene sheets, bearing hydroxyl and
epoxide functional groups on their basal planes and having carbonyl and carboxyl groups located
at the sheet edges. Due to the presence of these oxygen-containing functional groups, GO can
readily yield stable dispersion in water, consisting mostly of 1nmthick sheets. In terms of
mechanical properties, the elastic modulus and tensile strength of GO is around 32 Gpa and 130
Mpa, respectively. In this study various improvements that can be introduced to the cementitious
materials is discussed.
2. GRAPHENE OXIDE
2.1 GRAPHENE OXIDE

One of the advantages of the graphene oxide is its easy dispersability in water and other
organic solvents, as well as in different matrixes, due to the presence of the oxygen functionalities.
This remains as a very important property when mixing the material with ceramic or polymer
matrixes when trying to improve their electrical and mechanical properties.
On the other hand, in terms of electrical conductivity, graphene oxide is often described as
an electrical insulator, due to the disruption of its sp2 bonding networks. In order to recover the
honeycomb hexagonal lattice, and with it the electrical conductivity, the reduction of the graphene
oxide has to be achieved. It has to be taken into account that once most of the oxygen groups are
removed, the reduced graphene oxide obtained is more difficult to disperse due to its tendency to
create aggregates.
Functionalization of graphene oxide can fundamentally change graphene oxide’s
properties. The resulting chemically modified graphene could then potentially become much more
adaptable for a lot of applications. There are many ways in which graphene oxide can be
functionalized, depending on the desired application. For optoelectronics, bio devices or as a drug-
delivery material, for example, it is possible to substitute amines for the organic covalent

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Functionalization of graphene to increase the dispersability of chemically modified graphene in
organic solvents. It has also been proved that porphyrin-functionalized primary amines and
fullerene-functionalized secondary amines could be attached to graphene oxide platelets,
ultimately increasing nonlinear optical performance.
In order for graphene oxide to be usable as an intermediary in the creation of monolayer or
few-layer graphene sheets, it is important to develop an oxidization and reduction process that is
able to separate individual carbon layers and then isolate them without modifying their structure.
So far, while the chemical reduction of graphene oxide is currently seen as the most suitable
method of mass production of graphene, it has been difficult for scientists to complete the task of
producing graphene sheets of the same quality as mechanical exfoliation, for example, but on a
much larger scale. Once this issue is overcome, we can expect to see graphene become much more
widely used in commercial and industrial applications. Typical nanofillers include nanoparticles,
CNTs and GO that have the potential to improve the strength and durability of concretes. Their
sizes are compared with the typical components in cement and concrete as shown in Figure 1.

Figure 1: Comparison of Nano fillers with supplementary cementitious material and aggregates
in concrete

2.2 SYNTHESIS OF GRAPHENE OXIDE

GO was prepared according to the modified Hummer method. The synthesis of grapheme
oxide is shown in flow chart in Figure 4 . 5 g of graphite and 2.5 g of NaNO3 were mixed with

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108 mL H2SO4 and 12 mL H3PO4 and stirred in an ice bath for 10 min. Next, 15 g of KMnO4

were slowly added so that the temperature of the mixture remained below 5°C. The suspension
was then reacted for 2 h in an ice bath and stirred for 60 min before again being stirred in a 40°C
water bath for 60 min. The temperature of the mixture was adjusted to a constant 98°C for 60 min
while water was added continuously. Deionized water was further added so that the volume of the
suspension was 400 mL. 15 mL of H2O2 was added after 5 min. The reaction product was

centrifuged and washed with deionized water and 5% HCl solution repeatedly. Finally, the product
was dried at 60°C.

Figure 2: Diluted GO solution Figure 3: GO SHEET

Figure 4: Flow chart of synthesis of graphene Oxide

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2.3 PHYSICAL PROPERTIES OF GRAPHENE OXIDE
The physical properties of Graphene Oxide Nano Platelets is described in the table 3.
Table 1 properties of graphene oxide
ELASTIC MODULUS (GPa) 23-42
TENSILE STRENGTH (GPa) ~0.13
ELONGATION AT BREAK (%) 0.6
DENSITY (kg/m3) 1800
DIAMETER/THICKNESS (nm) ~0.67
SURFACE AREA (m2/kg) 700-1500
ASPECT RATIO 1500-45000

3 ADVANTAGE AND DISADVANTAGE

3.1 ADVANTAGES OF “GRAPHENE OXIDE REINFORCED PORTLAND CEMENT”
 Several researchers have found that the addition of CNTs results in little change in strength
or even a deterioration of the composite in some cases. The reasons for this are generally
attributed to the poor dispersion of CNTs and weak bonding between the CNTs and the
cement matrix while, the oxygen functional groups, attached on the basal planes and edges
of GO sheets, significantly alter the van der Waals interactions between the GO sheets and
therefore improve their dispersion in water.
 The length of CNTs can be up to centimeters, which gives an aspect ratio exceeding 1000
while the aspect ratio of a single graphene sheet can reach more than 2000.
 Value of surface area of a single graphene sheet can theoretically reach 2600 m 2/g, which
is much higher than those of CNTs.
 GO can be easily acquired from natural graphite flakes (inexpensive source).
 The ability to improve matrix durability.
 To- reduce the quantity of steel reinforcement required in cementitious matrix structures.
 Allow adoption of thinner and lighter concrete structures, allowing for new architectural
designs.
 Relatively low weight percentage levels of graphene oxide such as between 0.01% to 0.5%
by weight of the OPC is required.
 Resistance too many environmental deterioration attack.

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3.2 DISADVANTAGES OF “GRAPHENE OXIDE REINFORCED PORTLAND
CEMENT”
 It reduces the workability.
 GO produce when at laboratory level it procedure make it expensive.

4 EXPERIMENTAL STUDY REPORT

Various experimental studies have been done on cementitious materials using graphene
oxide. Some of the important studies done on this topic is discussed below.
4.1 EXPERIMENTAL STUDY REPORT 1
Experiments on cement were conducted by Mr.Qin Wang and Mr.Jian Wang for their
research paper “influence of graphene oxide additions on the microstructure and mechanical
strength of cement” is discussed here. The various experiments conducted by them is explained
below.
 Test for strength of the cement paste and mortar
The compressive strength, flexural strength of the cement paste and mortar is tested
according to GB/T17617-2007 “Test methods of strength of cement mortar. The mix proportion
for cement paste and mortar in given on table 4 and table 5.
 Setting time of cement paste
The setting time of the cement paste was tested according to GB/T1346-2001 “test methods
of water requirement of normal consistency, setting time, stability of cement paste.
 Heat of hydration of the cement
The heat of hydration of cement was characterized by a Toni CAL cement heat of hydration
meter. The hydration time was chosen to be72 h at 25 ℃ with a cement weight of 10 g and a W/C
ratio of 0.5.
 Test for viscosity of cement paste
The viscosity of the cement paste was tested by NDJ-5S digital rotary viscosity meter. Due
to the limit of the non-Newtonian fluidity of the cement paste, the results of viscosity are used only
by comparison.
 Test for fluidity of cement paste
The fluidity of cement paste was measured according to GB/T8077-2000 “Test methods of
concrete admixture homogeneity.

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  Test for fluidity of the cement mortar
The fluidity of the cement mortar was measured according to GB/T2419-2005 “Test
methods of fluidity of cement mortar”.
The mixing proportion of cement paste was designed according to GB/T8077-2000 “Test
methods of concrete admixtures homogeneity. The dosage of water-reducing agent is 0.5% of
cement. After testing the fluidity, viscosity and setting time of the cement paste, the cement paste
was put into a mold (40 mm×40 mm×160 mm) and maintained at standard conditions. The mixing
proportion is shown in Table 2.
Table 2 mix proportion design of cement paste with different dosage of GO
Dosage of GO (w/ %) Cement (g) PC (g) Water (mL)
0 87
0.01 79.5
0.02 300 1.5 72
0.03 64.5
0.04 57
0.05 49.5
The mixing proportion of cement mortar was designed according to GB/T2419-2005 “Test
methods of fluidity of cement mortar”. The ratio of water to cement (W/C) is 0.37, the dosage of
water-reducing agent is 3.5 g, and the dosage of antifoaming agents is 2 g. After testing the fluidity
of the cement mortar, the cement mortar was put into a mold (40 mm×40 mm×160 mm) for curing
under a standard condition. Detail mixing proportion is shown in Table 3.
Table 3 mix proportion design of mortar with different dosage of GO
Dosage of GO (w/ %) Cement (g) PC (g) Standard sand (g) Water (mL)

0 165
0.01 150
0.02 450 3.5 1350 72
0.03 64.5
0.04 57
0.05 49.5

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 The influence of GO addition on the fluidity, viscosity and setting time of the cement paste
are shown in Table 4. From Table 4, it can be seen that with the increase of GO dosage, the fluidity
of cement paste decreases, the viscosity of cement paste increases and the setting time of cement
paste is shortened. Especially, when the GO addition is up to0.03%, there is an evident change in
the fluidity, viscosity and setting time. This illustrates that the GO addition may make the cement
paste thicker and may accelerate the hydration of the cement. The decrease of fluidity and increase
of viscosity may be attributed to the nanometer size effect and surface chemistry of GO.
Table 4 Effect of GO on cement paste properties
Dosage of GO (w/%) 0 0.01 0.02 0.03 0.04 0.05

Cement paste fluidity (mm) 236 187 201 92 81 70

Apparent viscosity (mpa.s) 988.5 1200.7 2268.8 5154.4 12788.4 19284.0

initial setting time 170 170 165 155 140 130

Final setting time 330 325 320 305 310 300

The influence of GO addition on the fluidity of the cement mortar is shown in Table 6.
From Table 5, it can be seen that GO also reduces the fluidity of the cement mortar, which is similar
to the result obtained for the cement paste.
Table 5 Effect of GO on mortar fluidity
Dosage of GO(w/%) 0 0.01 0.02 0.03 0.04 0.05
Mortar fluidity (mm) 197 196 187 188 172 167

The influence of GO addition on the hydration heat of cement and rate of heat release are
shown in Figure 5 and Figure 6. From Figure 5 and Figure 6, it can be observed that the hydration
heat of cement during 3 d decreases first and levels off thereafter. At a dosage of 0.02%, the rate
of heat release and the total amount of heat release have a sharp decrease over50%. Although with
the increase of the, dosage of GO, the rate of heat release and the total amount of heat release
gradually decrease and level off with the dosage of GO. From Figure 6, it is found that the heat
release curves of hydration at the different GO dosages, the occurrence time and the duration time
of hydration reaction all stages and the shape of curves are all similar to each other with no other
peak of heat release observed, indicating that the GO addition doses not retard the occurrence of

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the peak of heat evolution and, the mechanism of hydration heat reduction of cement is different
from that of silicon fume and fly ash. This may be correlated to the physico-chemical interaction
of GO with cement during the hydration. The high specific surface energy and oxygen functional
groups of GO may promote the hydration procedure through adsorption of the ion in the hydration
system and accelerate nucleation, growth and phase separation of the hydrated crystalline
compounds at early hydration stages. This may result in the reduction of the total amount of heat
released.

Figure 5: Effect of GO on cement hydration exothermic rate.

Figure 6: Effect of GO on cement hydration heat.

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 The influence of GO addition on the compressive strength and flexural strength of the
cement paste and mortar at different ages are shown in Figure 7 and Figure 8 respectively. From
Figure 7, it can be seen that with the increase of dosage of GO, the compressive and flexural
strength of the hardened cement paste all increase. When the dosage of GO is 0.05%,the flexural
strength increase by 86.1%, 68.5% and90.5% and the compressive strength by 52.4, 46.5 and
40.4% at 3, 7 and 28 d, respectively compared with the sample with no GO. When the dosage of
GO is 0.05%, the flexural strength increase by 69.4, 106.4 and 70.5% and the compressive strength
by 43.2%, 33% and 24.4% at 3, 7 and 28 d, respectively, compared with the control groups. GO
has a more obvious effect on flexural strength than compressive strength for both the cement paste
and mortar.

Figure 7: The flexural and compression strength of Cement pastes with different dosage of GO

Figure 8: the flexural and compression strength of mortar with different dosage of GO.

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4.2 EXPERIMENTAL STUDY REPORT 2
The experiments on concrete done by M. Devasena and J. Karthikeyan for their report on
“investigation on strength properties of graphene oxide concrete” is discussed here. In this study
they have conducted test for compression strength, split tensile strength and flexural strength for
concrete.
Concrete cubes of size 150mm x 150mm x 150mm and cylinders of size 150mm diameter
and 300mm height were casted (the proportions of concrete given in table 6) to test the
compressive strength, the split tensile strength and flexural strength. Ordinary Portland cement, 53
Grade conforming to IS: 12269 – 1987. Specific gravity of cement is 3.15. Locally available river
sand confined Grading zone II of IS: 383-1970. Specific gravity of fine aggregate is 2.6. Locally
available crushed blue granite stones conforming to graded aggregate of nominal size 12.5 mm as
per IS: 383 – 1970. Its specific gravity is 2.75. Potable water as per IS 456-2000. Chemical
prepared from graphite powder and other chemicals to enhance the strength parameters of the
concrete. The mix design was done for M25 grade concrete based on the IS: 10262-2009.Water
cement ratio adopted as 0.50.
Table 6 Nominal mix proportions for the preparation of concrete cube
MIX % of Water in Cement Fine Coarse Graphene
Graphene litre (kg/m2) aggregate aggregate Oxide
Oxide (kg/m2) (kg/m2) (kg/m2)
M0 - 192 384 715 1113 -
M1 0.05 192 384 715 1113 0.19
M2 0.1 192 384 715 1113 0.38
M3 0.2 192 384 715 1113 0.76

The test results exhibit the increase in the strength with the addition of graphene oxide.
When compared with the nominal mix the other mixes shown increase in strength at the end of 28
days. Also the maximum increase in strength is obtained M3 mix which is having graphene oxide
in 0.1% of cement. 0.1% of GO is needed to improve flexural strength of an PPC matrix about 4%
and compressive strength about 11%. The test results for compressive strength, flexural strength
and split tensile strength at 7days, 14 days and 28 days are tabulated in table 7, table8 and table9
respestively. Also, graphs of the same are tabulated in figure 9, figure10 and figure 11.

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 Table 7 compressive strength test result

MIX GO BY % OF AVERAGE COMPRESSIVE STRENGTH MPa

CEMENT
7 days 14 days 28 days

M1 0 15.75 21.00 24.60

M2 0.05 15.40 21.25 25.30

M3 0.1 18.00 23.87 27.05

M4 0.2 17.12 22. 05 26.65

Fig 9. Compressive Strength results

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 Table 8 Flexural Strength Test Result

MIX GO BY % OF AVERAGE FLEXURAL STRENGTH MPa

CEMENT
7 days 14 days 28 days
M1 0 3.80 4.27 4.71

M2 0.05 3.77 4.33 4.76

M3 0.1 3.96 4.45 4.82

M4 0.2 3.65 4.30 4.74

Fig 10. Flexural Strength Results

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 Table 11 split tensile strength test result

MIX GO BY % OF AVERAGE SPLIT TENSILE STRENGTH MPA

CEMENT
7 days 14 days 28 days
M1 0 2.40 2.82 3.15

M2 0.05 2.30 2.65 3.07

M3 0.1 2.41 2.85 3.18

M4 0.2 2.33 2.57 3.05

Figure 11: Split Tensile Strength Results

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4.3 EXPERIMENTAL STUDY REPORT 3
The experiments conducted by Chang qing lin, Wei wei and Yun hang hu for their journal
on “catalytic behavior of graphene oxide for cement hydration process” is discussed below.
Ordinary Portland cement type II, was used in this work.
Four concrete samples were prepared by mixing 40 g cement, 120 g stand sand, 12 g water,
and 4 g polycarboxylate super- plasticizer (PC) solution ( that contains 0, 0.5, 1.5, and 2.5 wt.
%GO, respectively) as follows : GO was suspended in distilled water and sonicated for 3h until
the homogeneous solution was obtained. Then, polycarboxylate superplasticizer (PC), which is an
indispensably admixture for a cement composite to reduce water consumption without losing
fluidity of the cement paste, was added to the mixture. The water to cement ratio was kept the
same. Finally, the cement and sand were added.

Figure 12: Schematic diagram of catalytic mechanism of GO for cement hydration.

The oxygen functional groups of GO remain unchanged with the hydration time for all
cases. This indicates that the hydration of cement in the GO/cement composites did not cause any
change in GO functional groups. In other words, the acceleration of hydration by GO suggests that
GO would be a catalyst instead of a reactant for the cement hydration. This catalytic behavior of
GO for cement hydration can be explained as follows (Figure 12): The surface of GO possesses
rich oxygen functional groups (mainly –OH and –COOH). Those oxygen containing groups have
two main functions: (1) the active functional groups would be active sites to interact with cement,
and (2) the functional groups can absorb water molecules, generating a water reservoir and water
transport channels. When GO was highly dispersed in cement, C3A, C4AF, C3S, and C2S should
have a strong interaction with oxygen-containing functional groups of GO, namely, GO-connected
components (C3A, C4AF, C3S, and C2S) of cement can easily react with water molecules ad-
sorbed on functional groups of GO, forming crystal nucleuses of hydrates. Furthermore, water
molecules on GO constitute a water reservoir and thus water transport channels for the hydration
of C3A, C4AF, C3S, and C2S, accelerating the hydration rate.
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4.4 EXPERIMENTAL STUDY REPORT 4
Experiments conducted by Zhu Pan, Li He, Ling Qiu, Asghar Habibnejad Korayem, Gang Li,
Jun Wu Zhu, Frank Collins, Dan Li, Wen Hui Duan, and Ming Chien Wang for their journal “Mechanical
properties and microstructure of a graphene oxide-cement composite” is discussed here. The water-to-
cement ratio of all mixtures was kept at 0.5. For GO-cement, the GO sheets were added in the amount of
0.05% by weight of cement. The casting procedures for all samples are similar. The cement and liquid
(water or GO suspension) were placed in a plastic bowl and the cement slurries were mixed at 2000 rpm
for 5 min using a hand-mixer (Sanyo, SHM500, China). The mixture was then placed into a steel mold.
Each mold was vibrated for 15 to 30 seconds on a vibration table. All specimens were immediately covered
by polyethylene sheets in order to prevent loss of water from the samples. After 24 hours, the hardened
cement specimen was then remolded and cured in a calcium hydroxide bath to prevent lime leaching out
from the cement pastes. Different curing regimes were adopted for the specimens tested at different ages.
For specimens tested at an age of 7 days, they were cured over 7 days. For those tested at the ages of 28
and 56 days, the specimens were cured over 28 days. All the specimens were allowed to dry in the air for
12 hours before they were subjected to mechanical tests.
 Mechanical property tests
The flexural strength was measured following the procedure prescribed by ASTM C78/C78M-10.
Flexural strength tests were conducted on 15 mm x 15 mm x 80 mm prisms. The compressive strength
was measured following the procedure prescribed by ASTM C109/C109M-11b. Compressive strength
tests were conducted on 15 mm x 15 mm x 15 mm cubes. To obtain stress-strain curve in the post-
failure region, linear voltage displacement transducers (LVDTs) were used. Two LVDTs were used to
measure the vertical displacement of the specimen on the left and right sides and provided the average
axial strain. The strain of the specimens was further measured by a laser extensometer of LX 500.
 Ultrasonic pulse velocity measurement
Through a direct transmission mode, ultrasonic pulse velocities were measured by a
commercially available pulse meter with an associated transducer pair. The lightly greased
transducers were placed on two sides of the cube specimens (15 mm x 15 mm). As a result, the
travelling length of the ultrasonic pulse is the distance between opposite surface of specimens,
which was measured by using a vernier caliper with a minimum reading of 0.01 mm. By knowing
the path length, one can use the measured travel time (t) to calculate the pulse velocity (v) as v =
D/t, where D is the travel path length of ultrasound in the specimen.

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  Mini-slump test
The dimensions of the mini slump cone mould are: top diameter 19 mm, bottom diameter 38
mm, and height 58 mm. The mould-cone was placed firmly on a plastic sheet and filled with paste.
The paste was tamped down with a spatula to ensure compaction. The mould was removed
vertically, ensuring no lateral disturbance. After removal of the mould-cone, the horizontal spread
of the paste was measured by planimeter.
The results of compressive strength and flexural strength of GO-cement composite and plain
cement paste are summarized in Table 12. To check for reproducibility of the results, three samples
and four samples were tested for compressive test and flexural test, respectively.
The addition of GO sheets leads to a reduction in workability. When 0.05% GO is added, the
slump diameter is reduced by 41.7%. This result could be due to the large surface area of a GO
sheet that decreases the available water in fresh mix from wetting the GO sheets. Test results in
Table 12 shows that there were no significant differences in pulse transmission time between OPC and
GO-cement composite, indicating little entrapment of large air voids even though the GO-cement paste
workability was less that of OPC. The good homogeneity is further confirmed by the enhanced strength
of the GO-cement composite.
Table 12 Properties of Mixes
sample Mean Pulse Density Elastic Compressive Flexural
diameter velocity (kg/m2) modulus strength at strength at
of spread (m/sec) (GPa) the age of 7 the age of 7
area days (MPa) days (MPa)
(mm)
opc 68+/-5 2968+/-21 1821+/-45 3.48+/-0.17 31.3+/-1.5 4.7+/-0.25

GO-cement 48+/-3 2935+/-34 1787+/-35 3.70+/-0.13 38.8+/-1.8 7.0+/-0.2

The results of compressive strength and flexural strength of GO-cement composite and plain
cement paste are summarized in Table 12. The addition of GO enhances the compressive strength by
15% to 33% and flexural strength by 41% to 59% respectively. Variation in compressive strength with
age is shown in figure 13.

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 Figure 13: Effect of age on compressive strength
The stress-strain curves (under compression) for plain cement paste and GO reinforced
composite are shown in Figure 14. The elastic modulus, taken as the tangent to the stress-strain
curve under compression, is summarized in Table 1. In general, the elastic modulus of composites
is primarily affected by the stiffness and volume of components. A slight increase in elastic
modulus (from 3.48 to 3.70 GPa) may be due to the decrease in the number of original shrinkage
cracks owing to the GO arresting the cracking. Figure 15 shows the relationship between the
flexural stress and displacement for plain OPC paste and GO reinforced composite, respectively.
It can be seen that the area under stress displacement curves increased in the GO-cement
composite. A further examination of the curves (under compression) shows that the addition of GO
increased the area in pre-peak due to increase in the strain corresponding to peak stress. Before
reaching peak stress (ascending portion), nano-size cracks will propagate under load and form
continuous micro cracks around the peak of the stress-strain curve. The increased strain capacity
thus suggests that the initiation of micro cracks propagation is delayed by the presence of GO.

Figure 14: Typical stress-strain curves under compression at age of 28 days,

19
 Figure 15: Typical load-displacement curves under flexure at the age of 28 days
5. CONCLUSION
The GO addition can increase the viscosity and shorten the setting time of the cement paste.
When the dosage of GO is 0.05%, the viscosity increases sharply and the setting time is reduced
by 30 min. The fluidity of the cement mortar has the same tendency with the cement paste. The
GO addition can reduce of hydration heat of cement, which may be ascribed to the heat absorption
in oxidation-reduction reaction between GO and cement. When the dosage of GO is 0.05%, the
hydration heat of cement can be reduced by 54%. GO have a reinforcing and toughening effect on
the cement-based composites. The GO addition can remarkably increase the compressive and
flexural strength of the hardened cement paste and mortar, especially strength in the early stage.
When the dosage of GO is0.05%, the flexural strength of hardened cement paste increase by 86.1,
68.5and90.5% and the compressive strength by 52.4 %, 46.5 % and 40.4 % at 3, 7 and 28 d,
respectively. The flexural strength of hardened cement mortar increase by 69.4 %, 106.4 % and
70.5 % and the compressive strength by 43.2 %, 33 % and 24.4 % at 3, 7 and 28 d, respectively.
Addition of graphene oxide leads to an increase in compressive strength, tensile strength and
flexural strength. 0.1% of GO is needed to improve flexural strength of a PPC matrix about 4%
and compressive strength about 11%. The addition of GO improves the degree of hydration of the
cement paste and increases the density of the cement matrix, creating a more durable product. The
GO may take part in the hydration reaction of cement, accelerate the nucleation, growth and phase
separation of hydrated products, promote the hydration procedure, make the crystal aligned
regularly, which result in modification of pore structure and improvement of tightness.
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 Pore refinement by nanomaterials is highly desirable since it contributes to durability and
strength. Improvements in fracture toughness, compressive, flexural and tensile strengths due to
the addition of nanomaterials are consistently reported in experimental. Among all the Nano fillers,
GO appears to be an ideal candidate to enhance the properties of cement-based composite. The
excellent intrinsic properties of the 2D Nano sheet can strengthen the brittle cement matrix, similar
to CNTs. Furthermore, the oxygen-bearing functional groups are desirable for homogeneous
dispersion in cement, nucleation of C–S–H and densify the microstructure.
To fulfil the promise of newly developed nanomaterials in the construction industry, the
following issues should be addressed.
 Agglomeration of nanomaterials hinders their potential to improve the properties of
concrete. In this regard, the dispersion mechanism of nanomaterials is yet to be developed.
Although GO appears to be well-dispersed in water, there is no such guarantee of good
dispersion in the cement matrix.
 Admixtures play an important role to preserve the cement workability when nanomaterials
are added. However, detailed studies on the role of nanomaterials on the hydration and
interaction with the various phases of cement, including admixtures require attention.
 The durability aspect of cement and mortar containing nanomaterials provides an
interesting avenue for research. The behaviour of such composite under degradation such
as decarbonation, acid resistance, and sulphate resistance should be analysed.
 More in-depth studies are needed to prove the role of nanomaterials as nucleating sites
with the aid of nanoscale instrumentation as well as the atomistic modelling.

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6. REFERENCES:-
1. Chang qing Lin, Wei Wei, Yun Hang Hu (2016), Catalytic behavior of graphene oxide
for cement hydration process, Journal of Physics and Chemistry of Solids, Vol 89 pp 128–133.
2. Devasena.M, Karthikeyan.J (2015), “investigation on strength properties of graphene
oxide concrete”, International Journal of Engineering Science Invention Research & Development
Vol. I Issue VIII pp 308-310.
3. Qin Wang, Jian Wang, Chun-xiang Lu, Bo-wei Liu, Kun Zhang, Chong-zhi Li (2015),
“Influence of graphene oxide additions on the microstructure and mechanical strength of cement”,
New Carbon Materaials,Vol 30, pp 349-358.
4. Samuel Chuah, Zhu Pan, Jay G. Sanjayan, Chien Ming Wang, Wen Hui Duan (2014),
Nano reinforced cement and concrete composites and new perspective from graphene oxide,
Construction and Building Materials, Vol 73, pp 113-114.
5. Zhu Pan, Li He, Ling Qiu, Asghar Habibnejad Korayem, Gang Li, Jun Wu Zhu,
Frank Collins, Dan Li, Wen Hui Duan, Ming Chien Wang (2015), “Mechanical properties and
microstructure of a graphene oxide–cement composite”, Cement & concrete composites, Vol 58
pp140-147.

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