Experimental Investigation on Effect of Microsilica and...
Transcript of Experimental Investigation on Effect of Microsilica and...
214 Arshdeep Singh, Rattanjot Singh Dhillon
International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 4, Issue 6
June 2017
Experimental Investigation on Effect of Microsilica and
Nanosilica on Compressive Strength of High Strength Concrete
Arshdeep Singh1, Rattanjot Singh Dhillon2
1 Assistant Professor, Civil Engineering Department, PEC University of Technology, Chandigarh, India 2 Post Graduate Student, Civil Engineering Department, PEC University of Technology, Chandigarh, India
Abstract
This study concerns with the use of nanosilica and microsilica to improve the compressive strength of concrete.
Microsilica (MS) of much finer size then cement has been proven to be affective in improving mechanical properties of
concrete. With the advancement in nanotechnology, Nanosilica of even finer size than microsilica can also be used in
concrete as cement replacing material. An experimental investigation has been carried out by partially replacing the
cement with Nano Silica in varying percentage (i.e. 1%,2%,3%,4% & 5%) and micro silica in varying percentage (i.e.
5%,7%,9%,11%,13% &15%). In this study, cube of sizes 150mm x 150mm x150mm were cast for M-60 grade of concrete
and testing of the specimens were performed on compressive strength testing machine after curing of 7days and 28 days.
From the test result it was found that even very small of amount of NS (i.e. 2 to 3%) has substantial positive effects on the
compressive strength of concrete, but there was very high demand of super plasticizer. Moreover combined addition of
MS and NS has significant synergistic effects on the compressive strength (CS) of concrete and on the basis of results
obtained it can be advised that NS and MS should be added together to achieve the maximum strength of the concrete
however the effect of these material on workability of concrete can be compensated using high range water reducing
super plasticizer.
Key Words: Compressive strength(CS), Nanosilica (NS), Microsilica (MS).
1. INTRODUCTION
Concrete is the material of present as well as future
because of its low cost as well as good mechanical
properties. The wide use of concrete in structures
like buildings, bridges, airports, highways etc.
makes it one of the most investigated materials. Due
to cater the needs aroused from rapid population
explosion and the technology boom, there is an
urgent need to improve the strength and durability
characteristics of concrete using recent
advancements like nanotechnology in concrete[1].
Concrete is defined as "high-strength" solely on the
basis of compressive strength at a given age.
The ACI Committee on high strength concrete
revised the definition to cover mixtures with
specified design strength of 55 MPa or more. High
strength concretes are made with carefully selected
high-quality ingredients and optimized mixture
designs. The main requirement is that it should be
batched, mixed, placed, compacted and cured to the
high quality control. Typically, high strength
concretes will have a low water-cementing
materials ratio of 0.20 to 0.45. Superplasticizers are
usually used to make these concretes workable.
Production of high strength concrete may or may
not require special materials such as mineral
admixtures like microsilica, fly ash, ground
granulated blast furnace slag etc. The producer must
know the factors affecting compressive strength and
know how to vary those factors for best results. [2]
Most high strength concrete applications are
designed for compressive strengths of 70 MPa.
Commercial availability of high-strength concrete
provided an economical alternative to bulky
columns of conventional concrete for the lower
floors of high-rise buildings. [3]
1.1 Nanotechnology in Concrete
Nanotechnology applied to concrete includes the
use of nanomaterials like Nano Silica, Nano Fibers
etc. By adding the nanomaterials, concrete
composites with superior properties can be
produced. Addition of nanosilica in concretes and
mortars results in more efficient hydration of
cement.[3] Due to the pozzolanic activity,
215 Arshdeep Singh, Rattanjot Singh Dhillon
International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 4, Issue 6
June 2017
additional calcium silicate hydrates are formed to
generate more strength and to reduce free calcium
hydroxide. [4]
This also helps in reducing the cement requirement;
NS improves the microstructure and reduces the
water permeability of concrete thus making it more
durable. Use of Nano Silica in High Strength
Concrete and Self Compacting Concrete improves
the cohesiveness between the particles of concrete
and reduces segregation and bleeding. Concretes
with strengths as high as 66 MPa with high
workability, anti-bleeding properties and short de-
moulding time can be produced. Nano silica can be
used as an additive to eco concrete mixtures.[5,6] In
the case of eco concrete mixtures, industrial wastes
such as Flyash, Blast Furnace Slag are used as
admixtures at certain percentages as replacement to
cement. Certain problems like longer setting time,
lower compressive strength at higher percentages
can be overcome by adding Nano Silica which
improves these properties. Condensed Silica Fume
which is a by-product of metallurgical industries
when used as a partial replacement to cement has
been formed to contribute towards strength increase
of concrete in addition to other beneficial
properties.[7-10]
2. OBJECTIVES
The objective of this program is to investigate the
effect of partial replacement of cement with
siliceous materials i.e. nanosilica and microsilica on
the compressive strength of high strength concrete.
This will lead to the attainment in the increase of
compressive strength even by using the byproducts
such as microsilica whose cost is much lesser than
cement which reduces the construction cost.
The main objectives of the present study are as
mentioned below:
To study the effect of siliceous materials on
workability of concrete.
To investigate variation of compressive
strength of concrete containing different percentage
of microsilica i.e. 5%,7%,9%,11%,13% and 15%.
To investigate variation of compressive
strength of concrete containing different percentage
of nanosilica i.e. 1%,2%, 3%,4% and 5%.
To determine the suitable dose of nanosilica
and micro silica to achieve maximum strength.
To compare the test results of compressive
strength of concrete with and without siliceous
material.
3. MATERIALS USED
3.1 Nanosilica
Nanosilica is highly pozzolanic material which
contains very fine particles approximately 1000
times smaller than the cement particles. In the
present study nanosilica in colloidal form i.e.
nanosilica in dispersion with water in 40:60 ratios
has been used. Nanosilica used in the study has
been procured from Bee Chems, Kanpur, UP India.
Nanosilica is being manufactured for a range of
15% to 40% Active Nano content with particle size
in the range of 5-40 nm as shown in Table 3.1.
Table 3.1 Variety of Nanosilica available at
different active Nano content.
3.2 Microsilica
The microsilica used in the present study conforms
to IS 15388:2003. The micro-silica is extremely fine
particle, which exists in white color powder form.
Micro-silica has been procured from ELKEM Pahar
Ganj, New Delhi. The properties of microsilica as
provided by the manufacturer are shown in Table-
3.2.
Table-3.2: Physical Properties of Microsilica.
216 Arshdeep Singh, Rattanjot Singh Dhillon
International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 4, Issue 6
June 2017
3.3 Aggregates
Aggregate is the component of a composite
material that resists compressive stress and provides
bulk to the composite material. Both 20mm and 10
mm aggregates were available locally. Specific
gravity of coarse aggregate was found to be 2.63
and water absorption was 0.48%. Sand of Zone II
was used in this study. Specific gravity of fine
aggregates was found to be 2.64. [11,12]
3.4 Cement
Ordinary Portland cement (OPC) of 53 Grade, ACC
brand was procured and cement used was fresh,
without any lumps with uniformity in its shading.
The consistency of cement was tested to find its
initial and final setting time.[14,15] Specific gravity
and compressive strength for 7 and 28 days was
also found as depicted in Table 3.3.
Table-3.3: Properties of Ordinary Portland cement.
S.
No
.
Item Test
Result
As per
IS-8112-
2013
1. Normal
consistency (%)
36 -
2. Specific Gravity 3.10 3.15
3. Initial setting
time (minute)
150 > 30
4. Final setting
time (minute)
210 < 600
5.
Compressive
strength
(N/mm2)
3 days
7 days
28 days
34.50
44.20
55.33
>33
>43
>53
3.5 Superplasticizer
The superplasticizer was used for improvement in
workability and to reduce water cement ratio in
concrete. It was sulphonated naphthalene
formaldehyde with specific gravity 1.2.
4. EXPERIMENTAL PROGRAM
The test program was proposed to investigate the
effect of replacement of cement by Nanosilica and
Microsilica on the compressive strength of high
strength concrete. In first part of study, mix design
for M60 grade of concrete was prepared and casting
of cubes was done by partially replacing both
microsilica and nanosilica by weight of cement in
varying percentages (i.e. 5%,7%,9%,11%,13%
and15% for microsilica and 1%,2%, 3%,4% and 5%
for nanosilica). In second phase of the study, on the
basis of the test results a range of dosage was
selected suitably for both NS (i.e. 1%,2%, 3%) and
MS (i.e. 7%,9%,11%) for further investigation.
Casting of cubes was done to find the combined
dosage of Nanosilica and Microsilica in concrete
showing maximum compressive strength.
Workability of concrete was examined using slump
cone test apparatus for each mix. Slump test was
conducted as per codal provisions to investigate the
workability of concrete. [13] Finally, results
obtained from the study has been compared with the
control mix (CM) and conclusion were drawn. Mix
proportion and quantity of ingredients used in the
control mix is shown in Table 4.1.
Table-4.1: Mix design quantities and Proportion
ratio for control mix. S.No. Water
(Kg/m³) Cement
(Kg/m³)
Fine
Aggregate
s (Kg/m³)
Coarse
Aggregates
(Kg/m³)
Quantity 175 520 773 1044
Mix
Proportion
0.33 1 1.48 2.0
4.1 Testing Procedure
To examine the compressive strength of concrete,
cube moulds of size 150 mm x 150 mm x 150 mm
were cast. The test specimen were submerged in
clean water for proper curing after removing them
from the moulds. A 2000 kN limit Compression
Testing Machine (CTM) was used for compressive
strength testing at the rate of 5 kN/s and the
failure load in kN was observed on the monitor
screen as shown in Figure 4.1 . [16]
217 Arshdeep Singh, Rattanjot Singh Dhillon
International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 4, Issue 6
June 2017
Figure 4.1 Test Appratus for Compressive Strength
Testing.
4.2 Specimen Detail and Results
This experimental setup was proposed to examine
the behavior of high strength concrete in terms of
compressive strength after addition of nanosilica
and microsilica. Trial mixes were prepared and
casting of cubes of standard size of 150 mm x150
mm x 150 mm as shown in Figure 4.2, was done to
finalize a control mix for investigation. A total of 21
sets of different proportion were prepared
comprising both nanosilica and microsilica as
shown in Table 4.2. Compressive strength for each
set has been found after 7 days and 28 days curing
period.
Figure 4.2 Test Specimen placed after demoulding.
Table-4.2: Detail of specimens showing variation
in percentage change of MS, NS and compressive
strength results.
S.
No
Mix NS
(%)
MS(
%)
Compressiv
e Strength
(MPa)
7
day
28
day
1 CM CM 0 0 45.5 68.2
2
NS
NS1 1 0 50.2 69.6
3 NS2 2 0 54.5 75.1
4 NS3 3 0 54.9 72.2
5 NS4 4 0 48.9 64.0
6 NS5 5 0 46.9 61.9
7
MS
MS5 0 5 50.2 70.3
8 MS7 0 7 52.4 72.8
9 MS9 0 9 55.1 75.1
10 MS11 0 11 55.4 75.6
11 MS13 0 13 55.6 76.0
12 MS15 0 15 53.3 73.3
13
NS+MS
NS1+MS7 1 7 54 72.1
14 NS2+MS7 2 7 55.6 73.2
15 NS3+MS7 3 7 57.6 74.9
16 NS1+MS9 1 9 56.6 76.5
17 NS2+MS9 2 9 58.6 77.3
18 NS3+MS9 3 9 57.1 74.2
19 NS1+MS11 1 11 56.2 75.8
20 NS2+MS11 2 11 55.1 74.7
21 NS3+MS11 3 11 52.7 73.8
5. DISCUSSION OF RESULTS
The workability of cement concrete was examined
using slump cone test. In case of control mix, the
slump obtained was 40-50 mm. With the addition
of small percentage (i.e. 1%) of nanosilica the
slump was reduced to 20-25 mm. In case of 3%
nanosilica the slump was minimized and hence
requirement of superplasticizer was increased. Same
results were obtained for microsilica and
requirement of superplasticizer dosage increased
with the increase in percentage of microsilica to
obtain same slump value. It was observed from the
compression test results of cubes that compressive
strength increases as the percentage variation of
218 Arshdeep Singh, Rattanjot Singh Dhillon
International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 4, Issue 6
June 2017
nanosilica and microsilica was increased. There was
decrease in compressive strength when replacement
of cement with nanosilica was 4-5% but for
microsilica it showed an increasing pattern as
shown in Figure 5.1.
Improvement in the hydration process occurs due
fineness of nanosilica and hence the early age
strength of concrete increases. As shown in Figure
5.1, it was observed that 7 days compressive
strength of concrete increases with the variation of
nanosilica from 1% to 3% and there was a decrease
in 28 days strength with 4% nanosilica. This may be
due to the high heat of hydration or less workability
of concrete at this percentage variation.
Figure-5.1: Compressive strength variation of
concrete at varying percentages of nanosilica after 7
days and 28 days.
It can be observed from Figure 5.2 that with the use
of nanosilica in concrete, compressive strength of
concrete increases. A maximum increase of 20%
was obtained in 7 days strength and 15% increase
was observed in 28 days strength. However, there
was decrease in strength at higher percentage of
nanosilica (i.e. 5%) and it may be due to decrease in
workability which leads to a harsh mix.
Figure-5.2: Percentage Change in Compressive
strength of concrete at varying percentages of
nanosilica after 7 days and 28 days.
Figure-5.3: Compressive strength variation of
concrete at varying percentages of microsilica after 7
days and 28 days.
Figure-5.4: Percentage Change in Compressive
strength of concrete at varying percentages of
microsilica after 7 days and 28 days.
Figure-5.5: Compressive strength variation of
concrete at varying percentages of both nanosilica
and microsilica after 7 days.
219 Arshdeep Singh, Rattanjot Singh Dhillon
International Journal of Engineering Technology Science and Research
IJETSR
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ISSN 2394 – 3386
Volume 4, Issue 6
June 2017
Figure-5.6: Compressive strength variation of
concrete at varying percentages of both nanosilica
and microsilica after 28days.
It can be seen in Figure 5.3 that with the use of
microsilica in concrete, improvement in
compressive strength found was even better than as
observed with the addition of nanosilica. Also, it
can be observed that overall trend of the curve is
increasing for both 7 days and 28 days strength.
However, as shown in Figure 5.4, the percentage
change in compressive strength was showing a
decreasing pattern at 15 % replacement which may
be improved with the help of retarding admixture or
adjustment in dosage of superplasticizer.
It can be noticed from Figure5.5 and Figure 5.6 that
with the use of smaller percentages of microsilica in
concrete containing nanosilica, continuous
improvement in compressive strength found was
found. However, at higher percentages change in
compressive strength was showing a decreasing
pattern because of high heat of hydration produced
due to increased fineness of mix. Hence, a suitable
dosage of nanosilica (i.e. 2-3%) in combination
with microsilica (i.e. 9-11%) may be used to obtain
the improved strength.
6. CONCLUSIONS
The experimental investigation presented in this
paper shows the effect of nanosilica and microsilica
on the compressive strength of high strength
concrete. From the results obtained, it can be
summarized that the compressive strength of high
strength concrete increases with the incorporation of
both nanosilica and microsilica. However,
improvement in early age strength i.e. 7 days was
found to be more as compared to 28 days strength.
Moreover, combined addition of nanosilica and
microsilica has significant synergistic effects on the
compressive strength of concrete.
ACKNOWLEDGMENT
Authors would like to thank PEC University Of
Technology for infrastructure facilities.
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International Journal of Engineering Technology Science and Research
IJETSR
www.ijetsr.com
ISSN 2394 – 3386
Volume 4, Issue 6
June 2017
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