Paper Title (use style - IRD India

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International Journal of Recent Advances in Engineering & Technology (IJRAET)

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ISSN (Online): 2347 - 2812, Volume-4, Issue -6, 2016 51

Effect of Steel Fibers on Compressive Strength of Flyash blended Concrete

1Priyanka Ramkripal Singh, ²N.D.Shah

1Civil Engineering Department, C. U. Shah University, Surendranagar, Gujarat, India

2BITS Vadodara Babaria Institute of Technology, Gujarat, India

Abstract— Steel Fiber & Fly ash are common additives that can improve concrete performance. It is now well established that one of the important properties of Steel Fiber with fly ash Concrete is its superior resistance to cracking & crack propagation. This experimental investigation is to study the effects of replacement of cement (by weight) on M30 concrete with three percentage of fly ash and the effects of addition of steel fiber composite. A control mixture of proportion 1:1.7:2.6 with w/c of 0.45 was designed. Cement was replaced with three percentages (10%, 20%& 30%) of fly ash. Four percentage of steel fiber (0.5%, 1%, 1.5%& 2%) were used. UTM machine was used to determine the compressive strength of each block. The test results of this study confirmed that the addition of steel fiber & fly ash improves the compressive strength of concrete.

Keywords - Concrete, Steel Fiber, Fly Ash, Compressive Strength and MSA (Maximum Size Aggregate).

I. INTRODUCTION

Concrete is very strong in compression but weak in tension. As a concrete is a relatively brittle material, when subjected to normal stresses and impact loads. The tensile strength of concrete also depends upon on the widening of micro cracks existing in concrete subjected to tensile stress. Due to presence of cracks, steel fibers is generally taken as a solution to develop concrete in view of enhancing its compressive, tensile and flexural strength.

Fly ash is the fine powder which is the major waste material produced from many thermal power plants. The disposal of fly ash is the one of major issue for environmentalists as dumping of fly ash as a waste material may cause severe environmental problem.

Therefore, the utilization of fly ash as a low cost mineral admixture in concrete instead of dumping it as a waste material can have great beneficial effects. It can be used particularly in mass concrete application where main emphasis is to control the thermal expansion due to heat of hydration of cement paste and it also helps in

reducing thermal and shrinkage cracking of concrete at early ages.

The replacement of cement with fly ash in concrete also helps to conserve energy. Concrete is a composite material containing hydraulic cement, water, coarse aggregate and fine aggregate. The resulting material is a stone like structure which is formed by the chemical reaction of the cement and water. This stone like material is a brittle in nature, which does not possesses significant tensile strength. This weakness in the concrete makes it to crack under small loads, at the tensile end.

These cracks gradually propagate to the compression end of the member and finally, the member breaks. The formation of cracks in the concrete may also occur due to the drying shrinkage. These cracks are basically micro cracks. These cracks increase in size and magnitude as time elapses and the finally makes the concrete to fail.

II. ROLE OF STEEL FIBER IN FLYASH CONCRETE

A. Steel Fiber Fly Ash Concrete (SFFAC)

Steel Fiber Fly Ash Concrete (SFFAC) is mixtures of cement concrete containing short discrete, uniformly dispersed and randomly oriented suitable fibrous material which increases its structural fibrous material which increases its structural integrity.

B. Addition of Steel Fibers

The amount of Steel Fiber added to concrete mix is measured as percentages of the total weight of Concrete.

It varies within a specified range as to obtain the optimum strength.

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C. Composite Matrix(SFFAC)

The composites matrix that is obtained by combining cement, Fly ash, Aggregates and Steel fibers is known as

“Steel Fiber with fly ash Concrete”.

D. Crack Arresters

The fiber in the cement fly ash based matrix acts as cracks arresters, which restrict the growth of micro cracks and prevent these from enlarging under load.

III. MATERIALS

The cement used in this experimental work is 43 Grade Ordinary Portland cement. All properties of cement are tested by referring IS 12269-1987 Specification for 43 Grade Ordinary Portland cement.

TABLE I. PROPERTIES OF CEMENT

Property Value

Specific Gravity 3.15 Initial Setting Time 90 minutes Final Setting Time 600 minutes A. Fine Aggregate

Locally available sand passing through 4.75 mm IS sieve is used. The specific gravity of FA is 2.84 and its fineness modulus is 3.895.

B. Coarse Aggregate

20 MSA Crushed aggregate available from local sources has been used. The coarse aggregates with a maximum size of 20mm having the specific gravity value of 2.958 and fineness modulus of 7.136 are used as coarse aggregate.

10 MSA Crushed aggregate available from local sources has been used. The Coarse aggregates with a maximum size of 10mm having the specific gravity value of 3.016 and fineness modulus of 5.829 are used as coarse aggregate.

C. Water

Potable water has been used for the experimentation.

D. Steel Fibers

Steel Fiber with hooked ends is made using high-quality low carbon steel wire. It is a kind of high-performance steel fiber, with the characteristics of the high tensile strength, good toughness, low prices etc. The product is widely used in concrete strengthening. The dosage of steel fibers varies from 0.5% to 2% and is used by total weight of concrete. The length of steel fiber is 50 mm and its diameter is 0.7mm.

E. Fly Ash

Fly ash also known as flue-ash is one of the residues generated in combustion and comprises the fine particles that rise with the flue gases. Ash which does not rise is termed bottom ash. In an industrial context, fly ash usually refers to ash produced during combustion of coal.

Fly ash is generally captured by electrostatic precipitators or other particle filtration equipment before the flue gases reaches the chimneys of coal-fired power plants and together with bottom ash removed from the bottom of the furnace is in this case jointly known as coal ash.

IV. EXPERIMENTAL PROGRAM &

METHODOLOGY

Mix design is known as the selection of mix ingredients and the proportion required in a concrete mix. In the present study method for mix design is the Indian Standard Method. The mix design involves the calculation of the amount of cement, fine aggregate and coarse aggregate in addition to other related parameters dependent on the properties of constituent material. The modifications are made on the quantities of constituent material used to cast steel fiber with fly ash concrete.

The proportion of constituents as per Design Mix of M30 is (1:1.7:2.6) Cement: Sand: Coarse Aggregate.

TABLE II. MIX PROPORTION Grade Cement Fine

Agg.

Coarse Agg.

W/C Ratio M30 425.73

kg/m³

663.4 kg/m³

1151.4 kg/m³

0.45

A. Test Specimens

Cubes of size (100mm x 100mm x 100mm) and (150mm x 150mm x 150mm), Beams of size (700mm x 500mm x 500mm) and Cylinder of size (150mmx 300mm) were prepared using the moulds.

The samples were casted using the standard moulds. The specimens were casted using the four different percentages of fly ash (0%, 10%, 20%&30%) and with varying percentages of steel fibers (0.5%, 1%, 1.5% &

2%).The samples were de-moulded after 24 hours from casting. Cubes are kept in tank for 7, 21& 28 days.

Beams and Cylinders were kept for 28 days.

A total specimen of 144 cubes was casted for testing the properties such as compressive strength. The details of the specimens and their notation are given below in table.

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TABLE III. LIST OF SPECIMENS(CUBES)

S.N Notation Cubes

1 C1 (CONTROL MIX) 36

2 C2(10% FLY ASH) 36

3 C3(20% FLY ASH) 36

4 C4(30%FLY ASH) 36

The test which is performed on fresh concrete such as Slump are determined and Hardened properties such as Compressive, Flexural and Tensile Strength are presented and discussed below.

V. TEST RESULTS

On the fresh concrete Slump test has been performed and its value was determined whereas on the Hardened concrete properties such as Compressive, Flexural and Tensile Strength were determined.

Fresh Concrete or Plastic Concrete is a freshly mixed material which can be moulded into any shape. The relative quantities of cement, aggregates and water are mixed together to control the properties of concrete in the wet state as well as in hardened state.

A. Measurement of Workability

Tests adopted for measurement of Workability in the present investigation is Slump Test.

TABLE IV. SLU MP VALUE

S.N MIX (SF % & FA %) SLUMP (mm) 1 MS0 (0.0%&0.0%) 58

2 MS1 (0.5%&10%) 13 3 MS2 (0.5%&20%) 24 4 MS3 (0.5%&30%) 35 5 MS4 (1.0%&10%) 07 6 MS5 (1.0%&20%) 09 7 MS6 (1.0%&30%) 24 8 MS7 (1.5%&10%) 07 9 MS8 (1.5%&20%) 09 10 MS9 (1.5%&30%) 10 B. Compressive Strength

Compressive tests were conducted on cube, beam &

cylinder samples in accordance with the specification of Bureau of Indian Standards. The test results are given below:

TABLE V. COMPRESSIVE STRENGTH OF SFRC S.N Fly

Ash (%)

Steel Fiber (%)

7 days (N/mm²)

21 days (N/mm²)

28 days (N/mm²)

1 0% 0.5 27.43 33.57 40.39

1 31.63 39.42 42.35

1.5 30.20 37.06 40.73

2 28.45 34.66 38.07

2 10% 0.5 25.63 40.2 40.2

1 30.90 43.8 44.76

1.5 29.90 39.7 39.5

2 26.66 33.25 39.86

3 20% 0.5 22.07 31.67 33.09

1 30.45 40.41 41.36

1.5 26.86 36.73 40.86

2 25.03 30.9 37.13

4 30% 0.5 23.30 35.6 36.7

1 25.80 37.03 40.2

1.5 24.20 29.2 35.6

2 21.60 28.23 33.09

VI. DISCUSSION OF TEST RESULTS

With reference to the values of Table 7, it was observed that there is variation of Compressive Strength with the addition of steel fibers after 7 days, 21 days and 28 days of curing. It is found that with the increase in fiber content up to 1%, the strength is increasing i.e Compressive Strength is found to be higher at 1% fiber content and with further increase in fiber content the strength is decreasing.

VII. CONCLUSIONS

Following conclusion may be drawn based on the observations.

i. Addition of 1% steel fibers result in higher Compressive Strength and use of more than 1%

steel fibers will bring down the compressive strength.

ii. With 10% replacement of Fly ash and 1% addition of Steel fibers, it was observed that concrete is gaining maximum strength.

iii. There is an increment of 5.69 % in the compressive strength of concrete, when there is 10 % replacement of cement and 1% steel fiber addition.

iv. On the contrary, at 20 % replacement of cement, maximum compressive strength is observed at 1.5% addition of steel fibers.

v. At 30 % replacement of cement with fly ash, maximum compressive strength was obtained at 1% addition of steel fibers.

REFERENCES

[1] IS : 10262-2009, Recommended guidelines for Concrete mix design, Bureau of Indian Standards, New Delhi, India.

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[2] F- Fly Ash as Partial Replacement with Cement and Fine Aggregate in Mortar. Indian Journal of Engineering & Material Sciences,(2009), pp.

140– 144.

[3] Dr.R.N.Uma, “Experimental Investigation on Silica Fume as Partial Replacement of Cement in High Performance Concrete,” Sri Ramakrishna Institute of Technology, Coimbatore -10, India (2012), pp. 40.

[4] Miss Kwong Man, “The Use of Recycled Concrete Aggregate in Structural Concrete,”

Around South East Queensland. University of Southern Queensland. (2006), pp. 1-– 144.

[5] K. Arunachalam, “Experimental Investigation on High Performance Fly Ash Concrete in Normal and Aggressive Environment,”.

Thiagarajar College of Engineering, India (2004), pp. 180- 188.

[6] IS: 10262-1982, “Recommended guidelines for concrete mix design”, Indian Standards Institution, 1982.

[7] Hasan Sahan Arel, “Effects of Fly Ash Fineness on the Mechanical Properties of Concrete,” Indian Academy of Sciences, (2011), pp. 389–403.

[8] Coarse and fine aggregates from natural sources of concrete, IS 383: 1963, Bureau of Indian Standards, New Delhi.

[9] Indian standard methods of tests for aggregates for concrete, IS 2386(Part III), Bureau of Indian Standards, New Delhi.

[10] Indian Standard specification for ordinary and low heat Portland cement, IS 8112: 1989, Bureau of Indian Standards, New Delhi.

Figure 1 : Concrete cubes before testing for determination of Compressive Strength

Figure 2 : Concrete cubes after testing for Compressive Strength

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