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,



IJETSR

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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.



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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]

http://en.wikipedia.org/wiki/Composite_material

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IJETSR

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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



IJETSR

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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.


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.


concrete at varying percentages of both nanosilica

and microsilica after 7 days.



IJETSR

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Volume 4, Issue 6

June 2017


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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IJETSR

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Volume 4, Issue 6

June 2017

[11] IS: 383-1970 ‘‘Specification for coarse and fine

aggregates from natural sources for concrete”

Bureau of Indian Standards, New Delhi, India.

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[15] IS 5513:1996, ‘‘Vicat apparatus – specification”

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[16] IS 516:1959 “Method of test for strength of

concrete.”

experimental investigation on effect of microsilica and...

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