effect of steel fibres on the strength and behaviour of self compacting rubberised concrete

7/30/2019 Effect of Steel Fibres on the Strength and Behaviour of Self Compacting Rubberised Concrete

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International Journal of Civil Engineering and Technology (IJCIET), ISSN 0976 6308 (Print),

ISSN 0976 6316(Online) Volume 3, Issue 2, July- December (2012), IAEME

94

EFFECT OF STEEL FIBRES ON THE STRENGTH AND BEHAVIOUR

OF SELF COMPACTING RUBBERISED CONCRETE

N.Ganesan*, Bharati Raj, A.P.Shashikala & Nandini S.Nair

Dept. of Civil Engineering, National Institute of Technology Calicut, Kerala, India-673601

*Author to whom correspondence should be addressed. E-mail Id: [email protected]

Contact of other authors: [email protected], [email protected] ,[email protected]

ABSTRACT

The concepts of sustainability and sustainable development are receiving greater attentionnowadays as the causes of global warming and climatic change are discussed in various

forums. Since, concrete is the most widely used construction material on earth, sustainable

technologies for concrete construction allow for reduced cost, conservation of resources,

utilization of waste materials and the development of eco-friendly durable concrete.

Considering the above aspects, a cementitious composite known as Self Compacting

Rubberised Concrete (SCRC) was developed by adding scrap rubber to Self CompactingConcrete (SCC). The investigations on the engineering properties of SCRC revealed that there

is a systematic reduction in compressive, tensile and flexural strength of SCC on addition of

scrap rubber. In order to improve the foresaid engineering properties of SCRC, steel fibres

were added to the composite and the properties of Steel Fibre Reinforced Self Compacting

Rubberised Concrete (SFRSCRC) were evaluated. Also, a general regression equation

correlating various engineering properties of the composite was developed.

Keywords: brittleness, compressive strength, elasticity, flexural strength, rubber, self

compacting concrete, steel fibres

1. Introduction

The problem of waste accumulation exists worldwide, specifically in the densely populated

areas. Most of the non-degradable waste materials are left as stockpiles, used as landfill

material or illegally dumped in selected areas. Large quantities of this waste cannot be

eliminated. However, the environmental impact can be reduced by making more sustainable

use of this waste [1]. Researches into new and innovative uses of waste materials are

continuously advancing. These research efforts try to match societys need for safe and

economic disposal of waste materials.

The disposal of used tyres is a major environmental problem causing environmental hazards

throughout the world. Therefore, there is an urgent need to identify alternative outlets for

INTERNATIONAL JOURNAL OF CIVIL ENGINEERING ANDTECHNOLOGY (IJCIET)

ISSN 0976 6308 (Print)ISSN 0976 6316(Online)

Volume 3, Issue 2, July- December (2012), pp. 94-107

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95

these tyres, with the emphasis on recycling the waste tyres. The reuse of waste tyre rubber in

the production of concrete, where tyre rubber can be used as a partial replacement to natural

aggregates is an emerging field in this context. The use of rubber aggregates saves natural

resources and dumping spaces, and helps to maintain a clean environment. Hence, over the

past few years, various researches have been focused on the use of waste tyres in different

shapes and sizes in concrete [2]. Preliminary studies show that workable Rubberised PortlandCement Concrete (Rubcrete) mixtures can be made provided that appropriate percentages of

tyre rubber are used in such mixtures [3].

The development of Self Compacting Concrete (SCC) with the uniqueproperty of flowing

under its own weight by Okamura (1988) [4,5] was with the prime aim of solving the problem

of honeycombing and giving better finishes to structures [6], especially where congestion of

reinforcement occurs. One of the innovations in Self Compacting Concrete technology was

the replacement of aggregates using waste materials like rice husk ash, marble dust, recycled

aggregates, silica dust, scrap rubber, glass aggregates, etc to produce sustainable concretes

due to their superior structural performance, environmental friendliness and low impact on

energy utilization [7]. The possibility of developing SCC incorporating rubber aggregates was

a novel approach to combine the advantages of both SCC and Rubberised concrete. Self

Compacting Rubberised Concrete (SCRC) requires slightly higher amount of super plasticizerthan conventional SCC having the same water/powder ratios to attain the required self-

compacting properties [8]. Even though this seemed to be a promising technology in

controlling the microstructure of concrete to obtain more versatile and innovative mechanical

behavior, very few studies have been carried out so far on Self Compacting Rubberised

Concrete [3, 8-11].

Studies have revealed that the addition of steel fibres improves the engineering properties of

concrete like ductility, post crack resistance, energy absorption capacity etc. Inclusion of steel

fibres imparts pseudo-ductility to brittle concrete with a significant increase in the tensile

strain capacity which increases the flexural strength, cracking resistance and toughness

characteristics [12, 13]. These properties are highly required for the structures in the present

scenario of frequently occurring earthquakes. However, no attempts have been made so far toevaluate the effect of addition of steel fibres to Self Compacting Rubberised Concrete.

This paper focuses on the feasibility of adding steel fibres to Self Compacting Rubberised

Concrete. An attempt has been made to critically examine the engineering properties of

SFRSCRC mixtures, such as self compactability, compressive strength, split tensile strength,

flexural strength, modulus of elasticity and brittleness index.

2.1 Material

The materials used in this study include:

(i) Ordinary Portland cement conforming to IS: 12269-1987[13](ii) Fly ash with a normal consistency of 45% obtained from Neyveli Lignite Power Plant

and conforms to Type F as per ASTM C618 [14]

(iii) River sand passing through 4.75mm IS sieve conforming to grading zone II ofIS: 383-1970 [15] having specific gravity of 2.54

(iv) Coarse aggregate with a maximum size of 12mm and having a specific gravity of 2.77(v) Shredded scrap rubber with a maximum size of 4.75mm(vi) Crimped steel fibres having 0.45mm diameter and aspect ratio of 66


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96

2.2 Mix design for Self Compacting Concrete (SCC)

The mix design based on the method proposed by Nan et.al [16] which, gives an indication of

the target strength after 28 days of curing, was carried out for obtaining concrete compressive

strengths of 20, 30, 40 and 50MPa. The water powder ratio (w/p) was varied so as to obtain

SCC mixes of various strengths and the mixes were checked for self compactability as per the

EFNARC [17] acceptance criteria for SCC. Naphthalene based super plasticiser Structuro 201and viscosity modifying admixture (VMA) Calcium Sulphate dihydrate were added to impart

better workability and viscosity to the mix in order to avoid segregation. Table 1 gives the

details of the mix proportions of SCC.

2.3 Self Compacting Rubberised Concrete (SCRC)

Fine rubber was obtained by crushing the worn out tyres accumulated in the rubber waste

industry and sieved to get rubber particles with a maximum size of 4.75mm. The specific

gravity of fine rubber, thus obtained, was 1.14. In Self Compacting Rubberised Concrete

(SCRC), the fine aggregate was partially replaced by fine rubber and the percentage volume

of replacement (Rr) was 15%.

When fine aggregate was replaced with fine rubber, the mix was found to be less workable

and hence, the quantity of super plasticiser was increased, so that the mixes satisfy theacceptance criteria of SCC. The viscosity modifying admixture was also added at the rate of

0.01% of the water content for imparting better workability and viscosity to the mixes and to

avoid segregation. The details of the constituents of the mix are given in Table.1. The self

compactability of the mixes was checked by Flow test, V-funnel test and L-Box test. Cube

specimens of 150mm size were cast for the SCC and SCRC mixes and tested for the 7 and 28

day compressive strengths. The fresh and hardened properties of the mixes are given in

Table.2.

Table 1 Mix proportion for SCC & SCRC

Designation

Rr

(%)

Cement

(kg/m3)

Fly ash

(kg/m3)

Fine

Agg.(kg/m

3)

Coarse

Agg.(kg/m

3)

Scrap

Rubber(kg/m

3)

Super

plasticiser

(% ofpowdercontent)

VMA

(kg/m3) w/p

Water

(kg/m3)

SCC 20 0 196 211 887.00 710 - 0.50 - 0.50 202.00

SCRC 20 15 196 211 753.95 710 133.05 0.58 0.098 0.51 207.57

SCC 30 0 267 161 887.00 710 - 1.00 - 0.49 209.00

SCRC 30 15 267 161 753.95 710 133.05 1.26 0.134 0.50 214.00

SCC 40 0 339 130 887.00 710 - 1.30 - 0.44 205.00

SCRC 40 15 339 130 753.95 710 133.05 1.39 0.542 0.44 206.36

SCC 50 0 410 112 887.00 710 - 1.60 - 0.37 193.00

SCRC 50 15 410 112 753.95 710 133.05 1.66 0.533 0.38 198.36

Table 2 Self compactability of SCC and SCRC mixes

DesignationFlow

(mm)

V-funnel

time (s)

L-box

(mm)

Compressive Strength

(MPa)

7-days 28-days

SCC 20 754 7.0 0.86 13.91 27.56


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97

SCRC 20 740 9.0 0.84 10.17 19.56

SCC 30 750 8.0 0.86 25.60 37.50

SCRC 30 735 10.0 0.84 15.55 29.90

SCC 40 735 9.0 0.87 30.00 53.50

SCRC 40 720 11.0 0.85 20.85 40.10

SCC 50 723 10.5 0.89 37.50 62.00

SCRC 50 710 11.5 0.87 26.26 50.50

2.4 Steel Fibre Reinforced Self Compacting Rubberised Concrete (SFRSCRC)

Steel Fibre Reinforced Self Compacting Rubberised Concrete (SFRSCRC) was

obtained by adding crimped steel fibres having diameter 0.45mm, length 30mm

(aspect ratio 66) and ultimate tensile strength of 800MPa at volume fractions (Vf) of

0.25, 0.50, 0.75 and 1% to the SCRC mixes. Table.3 shows the mix proportions for the

SFRSCRC mixes.

Table 3 Mix proportion for SFRSCRC

Design

Strength

(MPa)

Vf

(%)

Cement

(kg/m3)

Fly ash

(kg/m3)

Fine

Agg.

(kg/m3)

Coarse

Agg.

(kg/m3)

Scrap

Rubber

(kg/m3)

Steel

fibres

(kg/m3)

Super

plasticizer

(% of

powder

content)

VMA

(kg/m3)

w/pWater

(kg/m3)

20

0.25 196 211 753.95 710 133.05 19.625 0.58 0.098 0.51 207.57

0.50 196 211 753.95 710 133.05 39.250 0.60 0.098 0.51 207.57

0.75 196 211 753.95 710 133.05 58.875 0.61 0.098 0.51 207.57

1 196 211 753.95 710 133.05 78.500 0.65 0.098 0.51 207.57

30

0.25 267 161 753.95 710 133.05 19.625 1.30 0.134 0.50 214.00

0.50 267 161 753.95 710 133.05 39.250 1.31 0.134 0.50 214.000.75 267 161 753.95 710 133.05 58.875 1.36 0.134 0.50 214.00

1 267 161 753.95 710 133.05 78.500 1.40 0.134 0.50 214.00

40

0.25 339 130 753.95 710 133.05 19.625 1.40 0.542 0.44 206.36

0.50 339 130 753.95 710 133.05 39.250 1.43 0.542 0.44 206.36

0.75 339 130 753.95 710 133.05 58.875 1.45 0.542 0.44 206.36

1 339 130 753.95 710 133.05 78.500 1.49 0.542 0.44 206.36

50

0.25 410 112 753.95 710 133.05 19.625 1.70 0.533 0.38 198.36

0.50 410 112 753.95 710 133.05 39.250 1.74 0.533 0.38 198.36

0.75 410 112 753.95 710 133.05 58.875 1.75 0.533 0.38 198.36

1 410 112 753.95 710 133.05 78.500 1.79 0.533 0.38 198.36

The following specimens were cast and tested for each mix to obtain the engineering

properties.

(i) 6 cube specimens of 150mm size to determine the unit weight and 28 daycompressive strength

(ii) 18 cylindrical specimens of 150mm and 300mm height for the split tensilestrength, modulus of elasticity and brittleness index


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International Journal of Civil En

ISSN 0976 6316(Online) Volum

(iii) 6 prisms of 100 x 1003. Test Results and Disc

3.1 Engineering propertie

The weights of SCC and SCdetermined. From Fig.1, it ca

lesser than that of convention

lightweight concrete can var

density range of 2300 to 250

rubber replacements of 15% o

to lightweight concrete.

Fig 1 De

Fig 2 Compressi

The compressive strength of

may be seen that, a decrease

rubberised composites in c

reduction in compressive stre

One of the possible reasons f

0

500

1000

1500

2000

2500

Density(kg/m

3)

0

10

20

30

40

50

60

70

CompressiveStrength(MPa)

ineering and Technology (IJCIET), ISSN 0976

3, Issue 2, July- December (2012), IAEME

x 500mm for the modulus of rupture

ssions

s of SCRC [19]

C cube specimens were obtained and then be seen that the average density of SC

l concrete and self compacting concrete. T

between 1200 to 2000kg/m3

compared t

0kg/m3. Hence, the self compacting concr

the fine aggregate volume can be consider

sity of SCC and SCRC specimens

ve strength of SCC and SCRC specimens

SCC and SCRC cube specimens are show

n compressive strength is observed for sel

mparison with the control specimens.

gth was found to be 23% for a rubber con

r this compressive strength reduction may

Mix Details

Mix Details

6308 (Print),

density wasC was 14%

e density of

the normal

te with fine

d equivalent

in Fig.2. It

compacting

he average

tent of 15%.

be the weak


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interface or the transition zon

aggregates. These weak intereventually grow to macro size

Split tensile strength test was

between the loading surface

applied until failure of the c

results of split tensile strength

strength of SCRC is similar to

split tensile strength is very

mainly due to the ease with

average reduction of 12 to

specimens. The decrease in s

factors that reduced the compr

Fig 3 Split Tens

Fig 4 Modulus

Modulus of rupture (extreme

under third-point loading. The

the range of 2.8 to 4.4N/mm2

Fig.4. The variation in modul

0

1

2

3

4

5

SplitTensileStrength(MPa)

0

1

2

3

4

5

ModulusofRupture(MPa)



e of the rubberised mortar and the conven

aces will act as the originators of microleading to failure under compression.

carried out on cylindrical specimens placed

of the compression testing machine. T

ylinder along the vertical diameter was o

are given in Fig.3. Although the variation o

that of the compressive strength, the rate o

uch lower when compared to the compres

hich the cracks can propagate under tensi

16% was observed in the split strengt

plit strength of SCRC could be attributed

essive strength.

le strength of SCC and SCRC specimens

f rupture of SCC and SCRC specimens

ibre stress in bending) was found out by t

flexural strength of the specimen was obse

for self compacting rubberised concrete as

s of rupture of Rubberised SCC is almost s

Mix Details

Mix Details

6308 (Print),

ional coarse

racks which

horizontally

e load was

served. The

split tensile

reduction in

sive strength

le loads. An

for SCRC

to the same

sting prisms

rved to be in

indicated in

imilar to that


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of its split tensile strength.

compressive strength of concr

It can be seen from Fig.5 tha

powder ratio, but, followed a

elastic modulus of SCRC was

This reduction in the elastic m

of the composite encountered

of rubber particles.

Fig 5 Modulus

Fig 6 BrittlenBrittleness Index of a concret

100% of the elastic defo

corresponding to the pre pecylindrical specimens were lo

unloaded and then reloaded u

based on the stress-strain hy

Lower values of brittleness in

0

5

10

15

20

25

30

35

Modulu

sofElasticity(GPa)

0

0.5

1

1.5

2

2.5

BrittlenessIndex



he strength in flexure increased with in

te, but at a very slow rate.

t the elastic modulus increased with decre

decreasing pattern when scrap rubber wa

found to be lesser than the control specim

odulus could be due to the reduced compres

owing to the relatively low specific gravity

f elasticity of SCC and SCRC specimens

ss Index of SCC and SCRC specimensspecimen in compression is defined as the

mation energy to irreversible deforma

k point of the stress-strain curve [20].aded up to 80% of the ultimate load carry

nder compression. The brittleness index w

teresis loops thus obtained and are indica

dex indicate higher ductile deformation of

Mix Details

Mix Details

6308 (Print),

rease in the

se in water-

added. The

ens by 19%.

sive strength

and modulus

ratio of 80 -

tion energy

he standarding capacity,

s calculated

ted in Fig.6.

the material.


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101

The addition of scrap rubber in concrete reduces the brittleness index values and

improves the ductility of concrete, thus, enabling a transition from a brittle material to

a ductile one. This is due to the better energy absorption capacity of rubber, which

leads to plastic deformations at the time of fracture. The concrete ductility was

enhanced by about 31% for SCRC specimens.

3.2 Fresh properties of SFRSCRC

Table.4 shows the variation of self compactability of SFRSCRC mixes with increase

in the volume fraction of steel fibre. From the table, it may be noted that the increase

in fibre content caused a gradual reduction of about 7% in the values of slump flow

when compared to SCRC, irrespective of the strength of concrete. Beyond a fibre

volume fraction of 0.5%, the deformability of the mix in terms of the flow value wasfound to decrease rapidly. The V-funnel time for SFRSCRC was almost same as that

of SCRC up to 0.5% volume fraction of steel fibres. Beyond 0.5%, the V-funnel timewas 11% higher than SCRC which sheds light on the enhanced apparent viscosity

(resistance to flow) of SFRSCRC. However, all the reported values were within the

desirable limits. The L-box values recorded from the test are given in the table, whichindicates that the passing ability ratio increased with increase in concrete strength

while it followed a decreasing trend with increasing fibre content, irrespective of the

compressive strength.

Table 4 Variation of self compactability with steel fibres

Vf(%)

Design Strength (MPa)

20 30 40 50 20 30 40 50 20 30 40 50

Flow value (mm) V-Funnel time (sec) L-box value (mm)

0.25 680 678 684 688 9 9 11 11 0.83 0.83 0.84 0.84

0.5 675 667 678 680 10 10 11 11 0.82 0.82 0.82 0.820.75 665 660 664 668 11 11 12 12 0.82 0.80 0.81 0.80

1 655 653 650 656 12 12 13 13 0.82 0.78 0.80 0.78

3.3 Hardened properties of SFRSCRC

3.3.1 Density

The weight of SFRSCRC cube specimens was measured and the density was

determined. The variation of density with the increasing fibre volume is given in Fig.7.

It was found that the density of the specimens increased with increase in fibre content.

The density of SFRSCRC is seen to fall in the range of 2000 to 2188kg/m3. Even

though the density was slightly higher for SFRSCRC specimens than SCRC, it was

lesser when compared to the density of SCC and conventional concrete which ranges

between 2300 to 2500 kg/m3.


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Fig 7 Var

3.3.2 Compressive Strength

The variation of compressiveAn increase in compressive st

volume fraction of 0.75%. Acompressive strength was no

addition of scrap rubber wa

presence of fibres. The averag

around 3.6%, 9.5% and 6.6%

For a volume fraction of 1%,

average of 16%. This decrea

entrapped air content when ficompressive strength if it do

content leads to a decreaseLessard [21], an increase of 1

reduce the compressive strenmost acceptable for volume fr

Fig 8 Variation

1700

1800

1900

2000

2100

2200

2300

0

Density(

kg/m3)

0

10

20

30

40

50

60

0CompressiveStrength(MPa)



iation of density with fibre content

strength with volume fraction of fibres is giength can be observed for SFRSCRC speci

t higher values of Vf, i.e., at 1%, in facted. The reduction in compressive strengt

countered by the enhanced binding pro

e increase in the compressive strength for a

for fibre contents of 0.25, 0.50 and 0.75%

the compressive strength was found to de

se in the strength may be attributed to th

bres are added. The fibre content slightlys not change the air content, while the pr

in the compressive strength. According t% in the air content in High Performance

th by 4%. The compressive strength wasction of 0.5%.

f compressive strength with fibre content

0.25 0.5 0.75 1

Fibre content

SCRC 20

SCRC 30

SCRC 40

SCRC 50

.25 0.5 0.75 1

Fibre content

SCRC 20

SCRC 30

SCRC 40

SCRC 50

6308 (Print),

ven in Fig.8.mens up to a

reduction indue to the

perty in the

l grades was

respectively.

crease by an

increase of

ncreases thesence of air

Aitcin andoncrete can

found to be


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103

3.3.3 Split Tensile Strength

The variation of split tensile strength with fibre content is shown in Fig.9. The split

tensile strength was found to increase with increase in fibre volume fraction. Theaverage increase in split tensile strengths for all grades was found to be around 1.2%,

4.7% 3.1% and 1.5% for fibre contents of 0.25, 0.50, 0.75 and 1% respectively.

Fig 9 Variation of split tensile strength with fibre content

3.3.4 Modulus of Rupture

Fig.10 shows the variation of flexural strength with fibre volume fraction. It can be

seen that the flexural strength increased with increase in fibre volume fraction for all

grades of concrete. The average increase in modulus of rupture for all grades was

found to be around 3.2%, 4.9%, 3.3% and 1.7% for fibre contents of 0.25, 0.50, 0.75

and 1% respectively. The flexural strength was found to increase with increasing fibre

content, despite the decrease in compressive strength. This increase in the rupture

modulus may be attributed to the improvement of fibre-matrix interfacial bond.

Fig 10 Variation of modulus of rupture with fibre content

3.3.5 Modulus of Elasticity

Modulus of elasticity is the most important parameter that represents the elastic

properties of concrete and depends mainly on the property of the paste and the

2

2.5

3

3.5

4

4.5

5

0 0.25 0.5 0.75 1

SplitTensileStrength(MPa)

Fibre content

SCRC 20

SCRC 30

SCRC 40

SCRC 50

2

2.5

3

3.5

4

4.5

5

0 0.25 0.5 0.75 1

Modulusofruptue(MPa)

Fibre content

SCRC 20

SCRC 30

SCRC 40

SCRC 50


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104

stiffness of the aggregates used. It can be seen from Fig.11 that the elastic modulus

increased with decrease in water-powder ratio, and also followed an increasing pattern

with higher fibre volume fractions. The elastic modulus of SFRSCRC was found to be

about 10% higher than that of SCRC. This increase in modulus of elasticity may be

due to the high modulus of elasticity of steel fibres. The bridging action of steel fibres

prevents the micro cracks from joining and thus arrests the sudden loss of strength.

Fig 11 Variation of modulus of elasticity with fibre content

3.3.6 Brittleness Index

From the variation of brittleness index with fibre content shown in Fig.12, it can be

noted that the brittleness index of SFRSCRC is about 4% less when compared to

SCRC. The decrease in brittleness index was notable at fibre volume fraction of 0.5%.

When compared to the SCC specimens, SFRSCRC showed an average decrease of

26% in brittleness index, which highlights the more ductile nature of rubberisedcomposites with steel fibres.

Fig 12 Variation of brittleness index with fibre content

0

5

10

15

20

25

30

35

0 0.25 0.5 0.75 1

ModulusofElasticity(GPa)

Fibre content

SCRC 20

SCRC 30

SCRC 40

SCRC 50

0.6

0.8

1

1.2

1.4

1.6

1.8

0 0.25 0.5 0.75 1

BrittlenessIndex

Fibre content

SCRC 20

SCRC 30

SCRC 40

SCRC 50


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105

4. Correlation of engineering properties of SFRSCRC with the compressive

strength

The split tensile strength, flexural strength, modulus of elasticity and the brittleness

index of Steel Fibre Reinforced Self Compacting Rubberised Concrete could be

expressed in terms of its compressive strength.

A correlation equation of the general form:

= (1)

has been formulated for all the engineering properties,

where represents the compressive strength of the mix and is a constant.

Yrepresents the engineering property of SFRSCRC.

The equations have correlation coefficients of 80% as shown in Fig.13. From thefigures, it could be noted that as the compressive strength increases, the engineering

properties of Steel Fibre Reinforced Rubberised Composites increases at a slow rate.

(a) Modulus of Elasticity (E) (b) Split Tensile Strength (STS)

(c) Modulus of Rupture (MR) (d) Brittleness Index (BI)

Fig 13 Correlation of engineering properties of SFRSCRC with compressive

strength

5. CONCLUSIONS

The critical investigation on the engineering properties of Steel Fibre Reinforced Self

Compacting Rubberised Concrete has paved way to realising the potentials of this

material for special application in the construction industry such as in seismic resistant

structures. The following conclusions were arrived at:

E = 4.0* (CS)0.5

R = 0.839

0

5

10

15

20

25

30

35

0 20 40 60

ModulusofElasticity(GPa)

Compressive Strength (MPa)

STS = 0.67* (CS)0.5

R = 0.850

0

1

2

3

4

5

0 20 40 60

SplitTensileStrength

(MPa)


MR = 0.7* (CS)0.5

R = 0.9240

1

2

3

4

5

0 20 40 60Modulusofrupture(MPa)


BI= 0.3* (CS)0.5

R = 0.8100

0.5

1

1.5

2

0 20 40 60

BrittlenessIndex



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106

1. Even though SFRSCRC was found to have density slightly greater than SCRC,it could be considered as a lightweight material owing to its reduced density in

comparison to conventional SCC as well as normal concrete. This property

would prove advantageous for seismic resistant structures.

2. The addition of steel fibres to SCRC up to a volume fraction of 0.5% has beenfound to have a beneficial effect on the strength and modulus of elasticity of

SCRC mixes. The compressive strength of SCRC was increased by about 10%

for a fibre volume fraction of 0.5%.

3. Addition of scrap rubber results in reduction of elastic modulus of concrete,which could be rectified to a certain extent by the addition of fibres. In

comparison to SCRC, the modulus of elasticity of SFRSCRC was found toimprove by an average of 10%, which could be attributed to the high modulus

of elasticity of steel fibres.

4. The brittleness index of SFRSCRC is very low compared to SCC mixes withand without rubber. This low brittle nature of SFRSCRC could be exploited

well by using it in congested areas like beam column joints, which are to bedesigned as ductile sections under seismic conditions.

All the engineering properties of SFRSCRC could be predicted from its 28-day

compressive strength with an effective correlation of 80% by means of regression

equations. It can be observed that all the evaluated properties are lying on the positive

side for SFRSCRC in comparison with Self Compacting Rubberised Concrete mixes.

Hence, it can be concluded that SFRSCRC offers numerous desirable characteristics

like improved strength, enhanced ductility, etc. for various structural applications.

Thus, SFRSCRC is having remarkable potentials to be considered as a sustainable

functional material for the construction industry.

REFERENCES

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2. Gregory Marvin Garrick B.S., Analysis and testing of waste tyre fibre modifiedconcrete, MS Thesis, Louisiana State University, May 2005.

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