influence of silica fume in enhancement of …...influence of silica fume in enhancement of...

INTERNATIONAL JOURNAL OF CIVIL AND STRUCTURAL ENGINEERING

Volume 2, No 1, 2011

© Copyright 2010 All rights reserved Integrated Publishing services

Research article ISSN 0976 – 4399

Received on June 2011 published on September 2011 43

Influence of Silica fume in enhancement of compressive strength,

flexural strength of steel fibers concrete and their relationship Pawade Prashant.Y

1, Nagarnaik P.B

2, Pande A.M

3

1- Research scholar, Department of Civil Engineering, G. H. Raisoni College of

Engineering, Nagpur, 440016

2- Professor, Department of Civil Engineering, G. H. Raisoni College of Engineering,

Nagpur

3- Professor, Department of Civil Engineering, Y.C.College of Engineering, Nagpur.

[email protected]

ABSTRACT

This paper shows the investigation on concrete due to the effect of silica fume with and

without steel fibers on Portland Pozzolona cement. In this study we used concrete mixes

with Silica Fume of 0%, 4%, 8%and 12% with addition of crimped steel fibers of two

diameters 0.5 mm Ø and 1.0 mm Ø with a constant aspect ratio of 60, at various

percentages as 0%, 0.5 %, 1.0 % and 1.5 % by the volume of concrete on M30 grade of

concrete. The effect of mineral admixture as cement replacement material with and

without steel fibers on mechanical properties were analyzed and compared with normal

concrete as well as silica fume concrete. In comparison, with control concrete the

replacement of 4%,8%,12% and 16% cement by silica fume showed 7.46%, 11.17%,

11.91%and 9.83% increase in compressive strength at 28 days of curing. The optimum

combined effect at 8% silica fume and 1.5% steel fiber with normal concrete the

maximum compressive strength increase at 0.5 mm Ø and 1.0 mm Ø steel fiber at 28

days of curing were 15.38% and 18.69%, the maximum flexural strength increase were

17.13% and 24.02%.The combined effect of silica fume at 4% & 12% with steel fiber at

0.5%, 1.0% & 1.5% of both diameters 0.5 mm Ø and 1.0 mm Ø at different ages of

curing are presented. As a result of the incorporation of crimped steel fibers, Silica fume

and Portland Pozzolona cement has produced a strong composite with superior crack

resistance, improved ductility and strength behavior prior to failure. On the basis of

regression analysis of large number of experimental results, the statistical model has been

developed. The proposed model was found to have good accuracy in estimating

relationship at 28 days and 90 days Compressive strength with Flexural Strength of

concrete.

Keywords: Portland Pozzolona Cement, Silica Fume, Steel Fibers, Compressive Strength,

Flexural Strength.

1. Introduction

1.1 Application of Steel Fiber in Concrete

It is necessary to develop the concrete of special properties. Portland Pozzolona cement

concrete possesses a very low tensile strength, limited ductility and little resistance to

Influence of Silica fume in enhancement of compressive strength, flexural strength of steel fibers

concrete and their relationship

Pawade Prashant.Y, Nagarnaik P.B, Pande A.M

International Journal of Civil and Structural Engineering

Volume 2 Issue 1 2011 44

cracking. Internal micro-cracks are inherently present in the concrete and its poor tensile

strength is due to propagation of such micro-cracks, leading to brittle failure of concrete.

Development of such type of concrete that has to meet special requirements. As strength

of concrete increases brittleness of concrete also increases. This weakness and brittleness

can be reduced by inclusion of steel Fiber in the concrete mix. These Fiber help to

transfer loads at internal micro cracks which called Fiber reinforced concrete. Steel fiber

reinforced concrete (SFRC) has gained acceptance for a variety of applications, namely

industrial floors, bridge decks, pavements, hydraulic and marine structures, precast

elements, nuclear vessels, repair and rehabilitation works, blast resistance structures It

has been reported that the addition of Steel fibers into concrete improves all engineering

properties of concrete such as tensile strength, Compressive strength, impact strength,

ductility and toughness.

The basic requirements of fibers for improving strength , high modulus of elasticity ,

adequate extensibility , good bond at the interface , chemical stability and durability The

mechanical properties of steel fibers reinforced concrete are influenced by the type of

fiber aspect ratio amount of fiber , strength of matrix ,size, shape and method of specimen

preparation , and size of aggregate.

1.2 Application of Silica Fume in Concrete

Silica fume also known as micro silica is a byproduct of the reduction of high-purity quartz with

coal in electric furnaces in the production of silicon and ferrosilicon alloys. Because of its

extreme fineness and high silica content, Silica Fume is a highly effective pozzolanic

material. Silica Fume is used in concrete to improve its properties like compressive

strength, bond strength, and abrasion resistance; reduces permeability; and therefore

helps in protecting reinforcing steel from corrosion.

1.3 Literature Review

A compressive review of literature related to Silica Fume and Steel Fiber concrete was

presented by ACI Committee 544 (ACI Committee, 544, 2006), Balaguru and Shah

(Balaguru P. N et al., 1992) . It included guidelines for design, mixing, placing and

finishing steel fiber reinforced concrete, reported that the addition of steel fibers in

concrete matrix improves all mechanical properties of concrete.

Steel fiber reinforced concrete under compression and Stress-strain curve for steel fiber

reinforced concrete in compression was done by Nataraja.C. Dhang, N. and Gupta, A.P.

(Nataraja M.C et al., 1998). They have proposed an equation to quantify the effect of

fiber on compressive strength of concrete in terms of fiber reinforcing parameter. In their

model the compressive strength ranging from 30 to 50 MPa, with fiber volume fraction of

0%, 0.5%, 0.75% and 1% and aspect ratio of 55 and 82 were used. In all the models only

a particular w/cm ratio with varying fiber content was used. The absolute strength values

have been dealt with in all the models and thus are valid for a particular w/cm ratio and

specimen parameter.






Mechanical properties of high-strength steel fiber-reinforced concrete was done by Song

P.S. and Hwang S.(Song P.S. et al., 2004).They have marked brittleness with low tensile

strength and strain capacities of high strength concrete can be overcome by addition of

steel fibers. The steel were added at the volume of 0.5%, 1.0%, 1.5% and 2.0%.The

compressive strength of fiber concrete reached a maximum at 1.5%volume fraction,

being 15.3%improvement over the HSC. The split tensile and Flexural Strength improved

98.3% and 126.6% at 2.0% volume fraction. Strength models were developed to predict the

compressive strength with split and flexural Strength of the fiber reinforced concrete.

Effect of GGBS and Silica Fume on mechanical Properties of Concrete Composites was

done by Palanisamay T and Meenambal T (Palanisamay T et al., 2008) . Carried out on

70 Mpa concrete with partial replacement of silica fume of 5, 10, 15, and 20% were

investigated. The compressive strength, split tensile and Flexural Strength were carried out

on 25 concrete mixes at the age of 28 days and compared with conventional concrete. The

optimum replacement of silica fume was at 10 % that showed compressive, split tensile and

Flexural Strength increased by 8%, 22% and 4.1% than control concrete.

2. Materials Used

2.1. Portland Pozzolona Cement

IS 1489(part 1):1991 containing 28% fly ash. The properties of cement tested were

Fineness (90µ Sieve) = 5 %, Normal consistency=31%, Soundness (mm) =0.50 Initial &

Final setting time =138minute & 216minute and 28 days Compressive strength= 55.63

Mpa.

2.2. Silica Fume

Silica fume having fineness by residue on 45 micron sieve = 0.8 %, specific gravity = 2.2,

Moisture Content =0.7% were used. The chemical analysis of silica fume (Grade 920-D):

silicon dioxide = 89.2%, LOI at 975[degrees] C = 1.7% and carbon = 0.92%, are

conforming to ASTM C1240-1999 standards.

2.3. Fine aggregate

Locally available river sand passing through 4.75 mm IS sieve, conforming to grading

zone-II of IS: 383-1970 was used. The physical Properties of sand like Fineness Modulus,

Specific Gravity, water absorption, Bulk Density, were 2.69, 2.61, 0.98% and 1536

Kg/m3

2.4. Course aggregate

Crushed natural rock stone aggregate of maximum nominal size up to 20 mm (A1) and

aggregate passing 10 mm (A2) were used. The combined specific gravity, Bulk Density

and water absorption of were 0.52 % @ 24 hrs. Fineness modulus of 20 mm &10 mm

aggregate were 7.96 & 6.13.






2.5. Steel Fiber

Crimped steel fibers conforming to ASTM A820-2001 has been used in this investigation.

Properties of crimped fibers are: 1) Length = 30 mm, diameter = 0.50 mm, and 2) Length

= 60 mm, diameter = 1.00 mm, with a constant aspect ratio = 60, ultimate tensile strength,

= 910 MPa to 1250 MPa and Elastic modulus of steel = 2.1 x 105

MPa.

2.6. Super Plasticizer

Sulphonated Naphthalene formaldehyde condensate-CONPLAST SP 430 super

plasticizer was used. It conforms to IS: 9103-1999 and has a specific gravity of 1.20.

2.7. Water

Water conforming to as per IS: 456-2000 was used for mixing as well as curing of

concrete specimens.

3. Experimental Set-up

Experimental Investigation is carried out to study the properties of M30 grade of concrete.

Silica Fume of 0%, 4%, 8%, and 12% with addition of two diameters of crimped steel

fibers with various percentage as 0%, 0.5 %, 1.0 % and 1.5 % by the volume of concrete

and 16%Silica fume without steel fibers, the mix proportion was (1:1.62:2.88) of cement

400 Kg/ m3

with W/C Ratio 0.42 and ratio of course aggregate A1:A2 was 70:30. The

150 X 150 X 150 mm cubes and 100 X 100 X 500 mm prisms (beams) were casted. The

compressive strength determination was the primary objective the 150 mm size of cubes

was tested at the age of 7 days, 28 days and 90 days. The flexural strength was carried out

on 100 mm x 100 mm x 500 mm size prisms under two point load condition at 28 days &

90days of curing. Three identical specimens were tested in all the mixtures and the entire

test.

4. Test Results and Discussions

4.1 Workability

The workability of silica fume with steel fiber concrete has found to decrease with

increase in silica & steel replacement so; it appeared that the addition of super

plasticizer might improve the workability. Super plasticizer was added range of 0.75 to

1.80% by weight of cementations materials for maintaining the slump up to 20mm.

4.2 Compressive strength.

1. Effect of silica fume

The effect of silica fume showed maximum increase in the compressive strength up to

12 % replacement. In this investigation the replacement level of 16% was included only

to study the trend of the behavior after 12% level.






In comparison with control concrete the replacement of 4%,8%,12% and 16% cement by

silica fume showed 4.04%,7.39%,8.01% and 5.83% increase in compressive strength at 7

days of curing. 7.46%, 11.17%, 11.91%and 9.83% increase in compressive strength at 28

days of curing. 7.99%, 12.00%, 12.62%, and 10.56% increase in compressive strength at

90 days of curing was showed in Table1./2.and Figure1.

In all result the increase in strength between 8% and 12% silica fume replacement was

marginal therefore the optimum replacement of cement by silica fume was consider as

8% for showing the graphical compression with Silica Fume concrete and their models

were predicted the strength of steel fiber.

2. Effect of silica fume with steel fibers

i) For 0.5 mm ø and 30 mm long fiber, of 8%silica fume at 7, 28 and 90days with

0.5 % steel fiber were 9.72%, 13.5%,14.35% and 1.0 %steel fiber were

10.85%,14.74%and 15.61%. And with 1.5 %steel fiber were 11.51%, 15.38%and

16.20%. Showed Figure2

ii) For 1.0 mm ø and 60 mm long fiber, at 8%silica fume at 7, 28 and

90dayswith0.5%steel fiber were 0.19%, 14.14%, 14.99%. & 1.0 %steel fiber were

12.83%, 16.82%, 17.74%. And with 1.5% steel fiber were 13.84%, 17.86% and

18.69%. Showed Figure 3.

Table 1: Compressive strength (N/mm2)

A) Compressive Strength (fc) without Silica Fume & Steel Fibers (Control

Concrete)

S.

NO.

Steel Silica 7

days

28

days

90

days

7

days

28

days

90

days

01 0.0 0.0 26.13 40.43 42.52 26.13 40.43 42.52

B) Compressive Strength (fcs and fcf)of Steel Fiber with and without Steel Fibers

Steel Fiber 4% Silica Fume 8% Silica Fume

Dia.&

Length

Vf (%)

7days 28 days 90 days 7days 28 days 90 days

01 0.0 27.08 42.56 45.06 27.74 43.71 46.62

02 0.5 27.46 43.17 45.70 28.13 44.33 47.29

03 1.0 27.72 43.57 46.12 28.40 44.76 47.72

04

0.5mm

ø &

30 mm 1.5 27.86 43.79 46.35 28.55 44.98 47.97

05 0.5 27.57 43.34 45.88 28.25 44.50 47.48

06 1.0 27.83 43.75 46.28 28.51 44.92 47.92

07

1.0mm

ø &

60mm 1.5 27.98 43.98 46.55 28.68 45.18 48.18

Steel Fiber 16% Silica Fume

7days 28 days 90 days

08 Dia.&

Length

Vf

(%)

0.0 27.64 43.52 46.38






Table 2: Compressive strength (N/mm2)

A) Compressive Strength (fc) without Silica Fume & Steel Fibers (Control

Concrete)

S.

NO.

Steel Silica 7

Days

28

days

90

Days

01 0.0 0.0 26.13 40.43 42.52

B) Compressive Strength (fcs and fcf)of Steel Fiber with and without Steel Fibers

Steel Fiber 12% Silica Fume

Dia.&

Length

Vf (%)

7days 28 days 90 days

01 0.0 27.89 43.94 46.91

02 0.5 28.29 44.56 47.58

03 1.0 28.56 45.01 48.02

04

0.5mm ø &

30 mm

1.5 28.70 45.22 48.26

05 0.5 28.40 44.76 47.77

06 1.0 28.66 45.16 48.20

07

1.0mm ø &

60mm

1.5 28.83 45.43 48.48

Figure 1: Compressive strength at 7, 28, 90 days of 0%, 4%, 8%, 12% & 16% of Silica

Fume.

4.3 Flexural Strength

1. Effect of silica fume

The flexural strength increase by replacement of 4%, 8%, 12% and






16% cement by silica fume showed 3.15%, 5.51%, 6.30% and 4.33% at 28 days of

curing and 3.88%, 6.28%, 6.84% and 4.62%increase in flexural strength at 90 days of

curing.

2. Effect of silica fume with steel fibers

i) For 0.5 mm ø and 30 mm long fiber, at 8%silica fume with 0.5 %steel fiber at 28

and 90days of flexural strength increase were 11.42%and 13.68%. at 8%silica

fume with 1.0 %steel fiber showed at 28 and 90days of flexural strength increase

were 14.76%and 17.01% at 8%silica fume with 1.5 %steel fiber showed at 7,28

and 90days of flexural strength increase were 17.13%and 19.41%,showed Figure

4.

ii) For 1.0 mm ø and 60 mm long fiber, at 8%silica fume with 0.5 %steel fiber at 28

and 90days of flexural strength increase were 14.76%and 17.56%. at 8%silica

fume with 1.0%steel fiber showed at 28 and 90days of flexural strength increase

were 20.28%and 22.55%. at 8%silica fume with 1.5 %steel fiber showed at 28

and 90days of flexural strength increase were 24.02%and 25.88%,showed Figure

5.

Figure 2: Compressive strength at 7,28,90 days of age at 8 % Silica Fume and 0,0.5,1.0

& 1.5% steel fiber of 0.5 mm Ø and Models were predicted the Compressive strength of

steel fiber.






Figure 3: Compressive strength at 7,28,90 days of age at 8 % Silica Fume and 0,0.5,1.0

& 1.5 % steel fiber of 1.0 mm Ø and Models were predicted the Comp. strength of steel

fiber.

Figure 4: Flexural strength at 28, 90 days of age at 8 % Silica Fume and 0, 0.5, 1.0 and

1.5% steel fiber of 0.5 mm Ø and Models were predicted the Flexural strength of steel

fiber.






Figure 5: Flexural strength at 28, 90 days of age at 8 % Silica Fume and 0, 0.5, 1.0 and

1.5% steel fiber of 1.0 mm Ø and Models were predicted the Flexural strength of steel

fiber.

4.4 Discussion on Relationship between Mechanical properties of concrete

Based on the test results, mathematical model was developed using graphical methods to

quantify the effect of silica fume and steel fiber content on interrelationship between

compressive strength and flexural strength of concrete, at 8% silica fume with steel fiber

of 0%, 0.5%, 1.0%, and 1.5% at 28 days and 90 days of curing. On examining the

validity of the proposed model, there exists a good correlation between the predicted

values by graphs and the experimental values was shown was showed in Figure.6 &

Figure7.

Figure 6: Relationship between Compressive Strength (fcf) and Flexural Strength (frf) at

28 days and 90 days for 8% silica fume and 0%, 0.5%1.0%, 1.5% steel Fiber of 0.5mm in

diameter.






Figure 7: Relationship between Compressive Strength (fcf) and Flexural Strength (frf) at

28 days and 90 days for 8% silica fume and 0%, 0.5%1.0%, 1.5% steel Fiber of 1.0 mm in

diameter.

Figure 8: Showed Compressive Strength Test Figure 9: Showed 1.0 mmØ Steel Fiber

Figure 10: Showed Flextural Strength Test Figure 11: Showed 1.0 mmØ Steel Fiber






5. Conclusions

Following conclusions were obtained base on the experimental investigations.

1. The weight density of concrete increase with increase in the steel fiber content.

2. Super plasticizer with dosage range of 0.75 to 1.80% by weight of cementations

materials (Cm = PPC + SF) has been used to maintain the adequate workability

of silica fume concrete and silica fume with steel fiber concrete mixes.

3. The compressive strength increases with the increase in silica fume compared

with normal concrete. The maximum increase in compressive strength was up to

8.01%, 11.92 and 12.62% at 7 days, 28 days and 90 days of curing for 12% of

silica fume replaced by PPC cement.

4. The increase of replacement levels of silica fume from 8% to 12% has not much

significant change on the development of compressive strength. Therefore the

optimum dosage of replacement of silica fume in the concrete was considered

8%.

5. The compressive strength increases with the addition of steel fiber was marginal

as compared with silica fume concrete.

6. The flexural strength increases with the addition of steel fiber was more as

compared with silica fume concrete. It was observed that the increases in flexural

strength is directly proportional to the fiber content and also the flexural

deflection decreases with increase in steel fiber than that of normal concrete.

7. Both the properties of concrete, compressive strength and flexural strength

increases by addition of 1.0mm diameter steel fiber than 0.5 mm diameter.

8. On the basis of regression analysis of large number of experimental results, the

statistical model showed in figures has been developed. The proposed model was

found to have good accuracy in estimating the 28 days and 90 days Compressive

strength and Flexural Strength, with their inter relationship at 0 %,4% 8% 12%

Silica Fume & 0%,0.5%,1.0%,1.5% Steel Fibers of both diameters.

6. Acknowledgement

The authors would like to express their sincere appreciation for providing steel fibers by

Shaktiman Stewols India (P) Ltd. and Super plasticizer by Black cat Enterprises (P) Ltd.

Nagpur.

7. References

1. ACI Committee, 544 (2006), "State-of-the-art report on fiber reinforced

concrete", ACI 544.1R-82, American Concrete Institute, Detroit.






2. Balaguru P. N., and Shah S. P., (1992) “Fiber Reinforced Cement

Composites”, McGraw-Hill: International Edition, New York.

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concrete under compression”, The Indian Concrete Journal, 26(3), pp 353-

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5. Song P.S. and Hwang S (2004), “Mechanical properties of high-strength steel

fiber- reinforced concrete “Construction and Building Materials, pp 669-676.

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