Evaluation of Strength Characteristics of Steel Fiber Reinforced Concrete added with Fly ash

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Evaluation of Strength Characteristics of Steel Fiber Reinforced Concrete added with Fly ash

Mohammed Hafis I P #1, Fazil P*2

Student1, Construction and Management Engineering, Department of Civil Engineering,

Ass.Professort2,Department of Civil Engineering, Cochin College of Engineering & Technology, Valanchery, Kerala

Abstract:- This project aims to investigate the mechanical properties of steel fiber reinforced concrete with the addition of fly ash. Steel fiber improves the tensile properties of concrete whereas fly ash acts as partial substitute for cement in concrete. This paper incorporates both the properties of steel fiber and fly ash. The study is carried out in M25 mix. Steel fibers varied from 0%.0.5%,1%,1.5% of different aspect ratios 20 and 30 and replacement of fly ash varies from 10%,20% and 30%. The specimens are generally tested for7 and 28 days and the behaviour of fly ash based steel fiber reinforced concrete were studied. The specimens are generally tested for compressive strength, tensile strength and flexural strength.

INTRODUCTION.

Concrete is the most commonly used material for civil engineering construction. Day by day the significance of concrete has developed and the limitations of concrete have been slowly but surely eliminated which increases the durability of concrete allowing a higher performance value to be achieved. Concrete is strong in compression but weak in tension. To overcome this weakness in concrete, steel reinforcement is utilized to carry the tensile forces and prevent any cracking or by pre-stressing the concrete so that it remains largely in compression under load. The introduction of steel fibers was brought in as an alternative to developing concrete in view of enhancing its flexural and tensile strengths. Although the basic governing principles between conventional reinforcement and fiber systems are identical, there are several characteristic variations; such as – fibers are generally short, closely spaced and dispersed throughout a given cross section. Steel fibers helps to reduce the problems associated with congestion of shear reinforcement such as interference with concrete compaction. These may attributed to the honeycombing and poor quality of concrete, particularly at critical sections such as beam-column junctions.

The rate of production of carbon dioxide released to the atmosphere is increasing due to the increased use of Portland cement in the construction. On the other side, fly ash is the waste material of coal based thermal power plant available abundantly but this poses disposal problem. Several hectares of valuable land are acquired by thermal power plants for the disposal of fly ash. The present investigation deals with the investigation of fiber reinforced concrete added with fly ash.

  1. FIBER REINFORCED CONCRETE

    Fiber reinforced concrete (FRC) is Portland cement concrete reinforced with more or less randomly distributed fibers. In Fiber reinforced concrete (FRC), thousands of

    small fibres are dispersed and distributed randomly in the concrete during mixing, and thus improve concrete properties in all directions. Fiber is a small piece of reinforcing material possessing certain characteristics properties. They can be circular, triangular or flat in cross- section. These fibers are produced from different materials like steel, plastic, glass, carbon and other natural materials. The fiber is often described by a convenient parameter called aspect ratio. The aspect ratio of the fiber is the ratio of its length to its diameter. The principle reason for incorporating fibers into a cement matrix is to increase the toughness and tensile strength and improve the cracking deformation characteristics of the resultant composite.

  2. OBJECTIVE OF THE STUDY

    1. To study the effect of flyash and steel fibers on the strength properties of concrete.

    2. To study the strength properties of flyash based SFRC and compared with normal concrete.

    3. To determine the maximum volume fraction of flyash and steel fibers.

    4. To study the effect of aspect ratio on flyash based steel fiber reinforced concrete.

  3. LITERATURE REVIEW

    K. Ramesh.et.al (2013) investigates the Mechanical Properties of the Fly ash concrete reinforced with steel fibers. Steel fibers varied from 0%, 0.5%, 1% and 1.5% by weight of cement and replacement of fly ash varied from 0%, 10%, 20%, 30% and 40% by weight of cement. The investigation programme included the determination of the optimum fiber content which can be provided in the concrete composites. Optimum fiber content was determined based on the Compressive strength, Split tensile strength, Flexural strength of the standard specimens. It is concluded that cement in concrete can be replaced upto 30% by fly ash with incorporation of steel fibers up to 1.5% to improve its strength characteristics.

    1. Madheswaran.et.al (2014) determines the compressive strength performance of the blended concrete combining different percentages of silica fume and fly ash and steel fiber as a partial replacement of cement. Fresh concretes containing 0.1% to 10% silica fume and 10% of fly ash as cement replacement in weight basis were prepared by modifying the reference Portland cement concrete. Fresh fiber reinforced concretes containing with different percentage of steel fibers (i.e. 0.5%, 1%, 1.5%, 2%) fiber in volume basis were prepared. This paper studies the workability and compressive strength properties. The

      results insure the effectiveness of minerals admixtures as fly ash, and silica fume to improve properties of concrete and to increase the resistance. The optimum dosage for partial replacement of cement by fly ash and silica fume is 10% and 8% for the addition of steel fiber is1.5%.

      SaiyadWaquar Husain (2015) measure compressive strengths of concrete of M30 grade with different steel fiber percentages and fly ash percentages. Concrete specimens with fiber contents of 0.5, 1.0 and 1.5 % by weight were tested. Fly ash contents in mixes ranged between 0 to 15% by weight. The investigation concludes that the maximum compressive strength of specimen after 28th day is 42.04MPa with 1% of fibers and 10% of fly ash. An increase of 21.49% in compressive strength is observed if fibers added to mix by 1% and fly ash using 10 %. There is an upward trend in strength up to 1 % of fibers but further increment of fibers causes the reduction in strength

  4. METHODOLOGY

    Based on the objectives, a methodology for present thesis work has been adopted

      1. The experiment is conducted in M25 grade concrete.

      2. Determination of material properties.

      3. Mix design is done as per IS 10262:2009.

      4. Casting of specimens with partial replacement of cement (0%, 10%, 20% and 30% flyash) with addition of steel fibers (0.5%, 1.0% and 1.5%).

      5. The mechanical properties of flyash based steel fiber reinforced concrete.

  5. EXPERIMENTAL TESTS

    1. Compression test

      Compression test on cubes and cylinders were performed on flyash based SFRC specimens to determine the compressive strength. At first the mix were prepared according to the mix design values. After that cubes and cylinder specimens were casted with replacement of cement with flyash in 10, 20 and 30% with an addition of 0.5,1 and 1.5% steel fibers of 20 and 30 aspect ratios. After curing of 7 and 28 days specimens are tested for compressive strength under compression testing machine.

      Fig 1: Compression test on SFRC specimen

    2. Split tensile strength test

      Steel fibers are generally used to increase the tensile strength of concrete. Steel fibers also helps to reduce the cracks developed in concrete due to plastic shrinkage and drying shrinkage. Concrete is not usually expected to resist direct tension because of its less tensile strength and brittle nature. Split tensile test is used to access the tensile strength of concrete with the addition of steel fibers. Mix were prepared according to the adopted mix design values. Specimens for split test were casted with replacement of cement by 10, 20 and 30% of flyash with an addition of

      0.5, 1and 1.5% steel fibers of 20 and 30 aspect ratios. After curing of 7 days and 28 days specimens were tested for split tensile test under compression testing machine. Cylinder specimens are placed horizontally between the loading surface of compression testing machine and the load were applied until the failure of specimens.

      Fig 2: Split tensile strength test on SFRC specimen

    3. Flexural strength test

    Steel fibers also help to increase the flexural strength of concrete. Mix were prepared according to the adopted mix design values. Specimens for flexural test were casted with replacement of cement by 10, 20 and 30% of flyash with an addition of 0.5, 1and 1.5% steel fibers of 20mm and 30mm aspect ratios. After curing of 7 days and 28 days specimens were tested for flexural test under UTM. . The load is applied on the specimens at a rate of loading of 400kg/min. The load is applied on the specimen till the failure of specimen.

    Fig 3: Flexural strength test on SFRC specimen

  6. EXPERIMENTAL RESULTS

    The experimental results of flyash based SFRC specimens of 28 days curing were shown in tables given below

    Table 2: Test results of 20 aspect ratio

    Specimen

    Cube strength (N/mm2)

    Cylinder strength (N/mm2)

    Tensile strength (N/mm2)

    Flexural strength (N/mm2)

    Control

    18.35

    14.71

    2.027

    2.03

    FA10SF0.5

    20.29

    16.69

    2.56

    2.76

    FA20SF0.5

    18.8

    14.89

    2.44

    2.41

    FA30SF0.5

    9.18

    7.54

    2.14

    2.09

    FA10SF1

    20.66

    16.69

    4.62

    3.70

    FA20SF1

    18.94

    14.77

    3.59

    3.18

    FA30SF1

    10.88

    8.39

    2.78

    2.53

    FA10SF1.5

    19.63

    15.36

    2.46

    2.58

    FA20SF1.5

    18.42

    14.55

    2.39

    2.33

    FA30SF1.5

    7.84

    6.69

    2.11

    2.09

    Specimen

    Cube strength (N/mm2)

    Cylinder strength (N/mm2)

    Tensile strength (N/mm2)

    Flexural strength (N/mm2)

    Control

    31.4

    22.24

    3.81

    5.06

    FA10SF0.5

    33.92

    25.46

    4.61

    5.76

    FA20SF0.5

    31.89

    24.89

    4.54

    5.51

    FA30SF0.5

    17.25

    13.2

    4.38

    5.27

    FA10SF1

    34.36

    26.21

    5.66

    5.89

    FA20SF1

    31.96

    25.56

    5.32

    5.62

    FA30SF1

    17.77

    14.23

    4.54

    5.33

    FA10SF1.5

    33.03

    25.84

    4.34

    5.58

    FA20SF1.5

    31.29

    25.03

    4.22

    5.39

    FA30SF1.5

    14.96

    11.03

    3.99

    5.14

    Specimen

    Cube strength (N/mm2)

    Cylinder strength (N/mm2)

    Tensile strength (N/mm2)

    Flexural strength (N/mm2)

    Control

    31.4

    22.24

    3.81

    5.06

    FA10SF0.5

    33.92

    25.46

    4.61

    5.76

    FA20SF0.5

    31.89

    24.89

    4.54

    5.51

    FA30SF0.5

    17.25

    13.2

    4.38

    5.27

    FA10SF1

    34.36

    26.21

    5.66

    5.89

    FA20SF1

    31.96

    25.56

    5.32

    5.62

    FA30SF1

    17.77

    14.23

    4.54

    5.33

    FA10SF1.5

    33.03

    25.84

    4.34

    5.58

    FA20SF1.5

    31.29

    25.03

    4.22

    5.39

    FA30SF1.5

    14.96

    11.03

    3.99

    5.14

    Table 3: Test results of 30 aspect ratio

    1. Relation between flexural strength and flyash content

      7

      6

  7. GRAPHICAL REPRESENTATION

      1. Comparison of 20 aspect ratio

        1) Relation between cube strength and flyash content

        40

        Cube strength in N/mm2

        Cube strength in N/mm2

        35

        5

        Flexural strength in N/mm2

        Flexural strength in N/mm2

        4

        3

        2

        1

        0

        0.5 1 1.5

        control specimen

        10% flyash

        20% flyash

        30% flyash

        30 control

        25 specimen

        Steel fiber

        20 10% flyash

        15

        Fig 6: Variation of flexural strength in 20 aspect ratio

        10

        5

        0

        0.5 1 1.5

        40

        35

        30

        25

        20

        40

        35

        30

        25

        20

        control

        specimen

        10% flyash

        control

        specimen

        10% flyash

        Cube strength in N/mm2

        Cube strength in N/mm2

        Steel fiber content

        20% flyash

        30% flyash

      2. Comparison of 30 aspect ratio

    1. Relation between cube strength and flyash content

      Fig 4: Variation of cube strength in 20 aspect ratio

      15

      15

      6

      5

      control

      4 specimen

      10% flyash

      3

      20% flyash

      2

      6

      5

      control

      4 specimen

      10% flyash

      3

      20% flyash

      2

      Tensile strength in N/mm2

      Tensile strength in N/mm2

    2. Relation between tensile strength and flyash content

    0

    0

    0.5

    1

    Steel fiber

    1.5

    0.5

    1

    Steel fiber

    1.5

    1

    1

    30% flyash

    30% flyash

    Fig 5: Variation of tensile strength in 20 aspect ratio

    0.5

    1

    Steel fiber

    1.5

    0.5

    1

    Steel fiber

    1.5

    20% flyash

    20% flyash

    10

    5

    0

    10

    5

    0

    Fig 7: Variation of cube strength in 30 aspect ratio

    1. Relation between tensile strength and flyash content

      7

      6

      5

      4

      3

      control

      specimen 10% flyash

      7

      6

      5

      4

      3

      control

      specimen 10% flyash

      1

      0

      1

      0

      0.5

      1

      1.5

      0.5

      1

      1.5

      Steel fiber content

      Steel fiber content

      2

      2

      20% flyash

      30% flyash

      20% flyash

      30% flyash

      Tensile strength in N/mm2

      Tensile strength in N/mm2

      Fig 8: Variation of tensile strength in 30 aspect ratio

    2. Relation between flexural strength and flyash content

    7

    Flexural strength in N/mm2

    Flexural strength in N/mm2

    6

    5

    1. The addition of steel fiber into the concrete significantly increases the strength properties of concrete.

    2. From the experiments conducted it was found out that optimum content of flyash is about 10% but replacement can be possible up to a percentage of 20.

    3. For 20 and 30 aspect ratio the optimum content of steel fiber is about 1%.

    4. As the aspect ratio increases strength properties of concrete also increases.

    5. Tensile strength and Flexural strength can be increased to 60% to 70% with the addition of steel fibers.

    6. It is concluded that cement in concrete can be replaced up to 20% by flyash with incorporation of steel fibers up to 1.0% to improve its strength characteristics and the optimum aspect ratio is found as 30.

    ACKNOWLEDGEMENT

    I am extremely thankful to our Principal Dr. S.P. Subramanian for giving us his consent for this project. I am indebtly thankful to my thesis guide Er. Sudheer.K.V, Head of the Department of civil engineering, for his constant help and support throughout the presentation of the thesis work by providing timely advices and guidance. I am also thankful to God almighty for all the blessing received during this endeavor. Last, but not least I am also thankful to all my friends for the support and encouragement they have given me during this thesis work.

    REFERENCES

    1. Falah A. Almottiri, Physical properties of steel fiber reinforced

      4

      3

      2

      1

      0

      0.5 1 1.5

      Steel fiber content

      Fig 9: Variation of flexural strength in 30 aspect ratio

      control specimen 10%

      flyash

      20%

      flyash

      cement composites with fly ash, Jordan Journal of Civil Engineering (Vol 5), 2011.

    2. Shende.A.M. Pande.A.M. Comparative study on steel fiber reinforced cum control concrete under flexural and deflection., International Journal on Applied Engineering and Research, 2011.

    3. Khadake S.N., KonapureC.G,An investigation of steel fiber reinforced concrete with fly ash, International Journal on Civil and Mechanical Engineering, 2012.

    4. Shende.A.M. Pande.A.M. Experimental Study on Steel Fiber Reinforced Concrete for M-40 Grade, International Refereed Journal of Engineering and Science (Vol 1), 2012.

    5. Prof. Jayeshkumar Pitroda.et.al, Experimental investigations on partial replacement of cement with fly ash in design mix concrete, International Journal of Advanced Engineering Technology (Vol3), 2012.

    6. Yu-Chen Ou.et.al, Compressive behavior of steel fiber reinforced concrete with a high reinforcing index, ASCE, 2012.

    7. Khadake S.N., Konapure C.G, An experimental study on steel fiber reinforced concrete with fly ash for M35 grade. IJERA

  8. SUMMARY AND CONCLUSIONS

The present Experimental investigation is to study the Mechanical Properties of the Fly ash concrete reinforced with steel fibers. Steel fibers of different aspect ratios 20 and 30mm varies from 0%, 0.5%, 1% and 1.5% by weight of cement and replacement of fly ash varies from 0%, 10%, 20% and 30% and 40%. From the experimental tests it was found out that

(Vol 3), 2013.

  1. R. Madheswaran, Experimental study on hardened concrete by using steel fibers with mineral admixture, IJCIET (Vol 5), 2014.

  2. Amit Rana, Some studies on steel fiber reinforced concrete,

    IJETAE (Vol 3), 2013.

  3. A.Sofi.et.al, An experimental investigation on flexural behavior of fiber reinforced pond ash modified concrete, Ain Shams Engineering Journal (Vol 1), 2015.

  4. Ramadoss Perumal, Correlation of compressive strength and other engineering properties of high performance steel fiber reinforced concrete, ASCE, 2015.

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