Experimental Investigation on Fibre Reinforced Concrete using Binding Wires


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Experimental Investigation on Fibre Reinforced Concrete using Binding Wires

Debasis Panda

Assistant Professor (NPIU-MHRD)

Dumka Engineering College Dumka, Jharkhand, India

Shubham Dutta

B.Tech student

Brainware Group of Institutions-SDET Barasat,Kolkata, India

Abstract- In recent days Fibre Reinforced Concrete (FRC) become more popular because of its better strength and crack arresting capacity. Fibre Reinforced Concrete (FRC) is a composite material consists of cement based matrix along with uniform or random distribution of short discrete fibres, which can be steel fibres, nylons, polyethylene etc.

In this present study the effects of addition of binding wires on the compressive strength, flexural strength and split tensile strength of concrete has been investigated experimentally. Different quantities of binding wires are added to the concrete to find out the optimum quantities of binding wires in which the FRC with binding wires is more effective in terms of strength and crack resistance capacity. The results of the study shows that the addition of binding wires as fibre can significantly increase the compressive, flexural as well as split tensile strength along with the crack arresting capacity. The results also gives a detail idea of optimum quantity of steel fibre that can be used in concrete production to get better strength and at the same time it will be more economical.

Keywords- Fibre reinforced concrete; binding wire; concrete properties; compressive and flexural strength; split tensile strength.

  1. INTRODUCTION

    Concrete is one of the most widely used construction material consumed after water. As concrete is brittle in nature is strong under compression but weak in tension. Therefore, a form of reinforcement is needed for structures stability. Steel bars are used as reinforcement in concrete structures. Still there is a possibility of crack formation internally or externally. Using fibers in concrete, the concrete can be modified in more ductile manner. In the FRC, at the time of mixing a number of small fibers are distributed in random orientation in the concrete Different kinds of materials can be used as fiber like various forms of steel fibres, glass, polymer, natural fiber, synthetic fiber etc. In accordance with the various physical properties of the fiber like type of fiber, quantity of fiber, length of fiber, aspect ratio (l/D), the properties of FRC like compressive strength, flexural strength, fatigue strength, can be modified. Steel fiber reinforced concrete (SFRC) is a composite material which can be made by adding steel fibers of different form, different size and shape in ordinary concrete matrix. Orientation of these fibers is commonly in random. The properties each of the fibers are different. Generally SFRC is very ductile in nature and particularly well suited for structures which are required to resist Shrinkage, fatigue strength, and temperature. Different research articles already showed that the steel fiber gives more strength than glass, polymer and other fibers. Here in this detailed study of fiber reinforced concrete with binding

    wires, we intend to find out if there is an optimum quantity of steel fibre that can be used in concrete production to get better strength and at the same time it will be more economical.

  2. EXPERIMENTAL INVESTIGATION

    1. Material Specifications

      The properties of concrete like workability, strength, durability, are very much influenced by the chemical and physical properties of each ingredients used for making the concrete. Portland slag cement, crushed stone chips as coarse aggregates, River sand as fine aggregates, portable drinking water, steel binding wires are used for this experimental study. Different tests were conducted to find out the properties of each ingredient with which design mix is performed.

    2. Cement

      For the experimental investigation Portland slag cement is used for making concrete specimens. Table-I shows the test results which were conducted as per IS: 4031-1988, to find out the properties of cement.

      TABLE-I PROPERTIES OF CEMENT

      Type

      PSC

      Brand

      ACC

      Consistency

      31%

      Initial Setting Time

      109 Minutes

      Final Setting Time

      305 Minutes

      Fineness

      3.426%

      Soundness

      0.33mm

      Specific Gravity

      2.93

    3. Coarse Aggregates

      Crushed angular stone chips of nominal maximum size of 20mm are used and different tests have been conducted as per IS: 383-1970 and IS: 2386-1963. Table-II shows the observations taken during the tests.

      TABLE-II PROPERTIES OF COARSE AGGREGATES

      Water absorption

      0.464%

      Specific Gravity

      2.86

      Crushing strength

      2.61N/mm2

    4. Fine Aggregates

      Different tests were conducted on natural river sand, which is used as fine aggregate, per IS: 383-1970 and IS: 2386-1963. Properties of sand are shown in Table-III

      TABLE-III PROPERTIES OF FINE AGGREGATES

      Water Absorption

      0.604%

      Specific Gravity

      2.72

      Zone

      IV

      Bulking of sand

      16%

    5. Fibres

      Carbon steel Binding wires are cutted into pieces and used as fibres in this present study. The detail properties of binding wires are given in Table-IV and Fig.1.

      TABLE-IV PROPERTIES OF BINDING WIRES

      Density

      7840kg/m3

      Diameter

      0.75 mm

      Length

      60 mm

      Aspect ratio

      80

      Ld

      1/8 of 60mm

    6. Design Mix

      For this present study M25 concrete is used. Using the test data of materials and as per IS 10262:2009, the mix design is carried out. All the specimens were casted using this design mix proportions. As per the design mix, the quantities required for 1m3 concrete is shown in Table-V.

      TABLE-V PROPORTION FOR 1M3CONCRETE

      Grade of Concrete

      M25

      Slump

      100mm

      Size of Coarse aggregate

      20mm

      Cement

      394 kg/m3

      Fine Aggregate

      581 kg/m3

      Coarse Aggregate

      1256 kg/m3

      Water Content

      197 kg/m3

      W/C ratio

      0.5

      Mix Design Ratio

      1 : 1.47 : 3.19

    7. Casting and Curing of Specimen

    To determine the effects of binding wire as a fire on compressive strength, split tensile strength and flexural strength of concrete, cubes of 150mm×150mm×150mm, cylinders of 150mm diameter and 300 mm height, beams of size 500mm×100mm×100mm were casted without fibre and with different quantities of fibre. Hand mixing is used for mixing the concrete without and with fibres to maintain the proper quantities of fibres in each specimen. Specimens were demoulded after 24 hour and cured for 28days under normal water. Details of specimens are given in Table-VI.

    TABLE-VI DETAILS OF SPECIMENS

    Specimens

    Name of test

    Quantities of fibre added kg/m3

    No. of specimens

    Cubes 150mm×150mm×150mm

    Compressive strength test

    0 kg/m3

    6 Nos.

    5 kg/m3

    6 Nos.

    10 kg/m3

    6 Nos.

    15 kg/m3

    6 Nos.

    20 kg/m3

    6 Nos.

    25 kg/m3

    6 Nos.

    30 kg/m3

    6Nos.

    Cylinders 150mm diameter and 300 mm height

    Split tensile test

    0 kg/m3

    6 Nos.

    5 kg/m3

    6 Nos.

    10 kg/m3

    6 Nos.

    15 kg/m3

    6 Nos.

    20 kg/m3

    6 Nos.

    25 kg/m3

    6 Nos.

    30 kg/m3

    6 Nos.

    Beams 500mm×100mm×100mm

    Flexural strength test

    0 kg/m3

    6 Nos.

    10 kg/m3

    6 Nos.

    15 kg/m3

    6 Nos.

    20 kg/m3

    6 Nos.

    25 kg/m3

    6 Nos.

    (a)

    (b)

    Fig.1: Binding wire as Fibre.

    (a)

    (b)

    Fig.1: Binding wire as Fibre.

  3. RESULTS AND DISCUSSIONS

    The objective of the present study was to find out the effects of addition of binding wires as fibres on concrete. For these three types of tests were conducted, compressive strength test on cubes, split tensile test on cylinders and flexural strength tests on beams, without and with different quantities of fibres added into the samples while casting.

    (a)Without fibres

    (b)With fibres

    Fig. 4. Crack pattern of cubes without and with fibres.

    (a)Without fibres

    (b)With fibres

    Fig. 4. Crack pattern of cubes without and with fibres.

    1. Compressive Strength Test

      Prepared cube samples without and with fibres are tested after 28 days curing as per IS 516-1959. The test results are shown in Table-VII and Figs-2 and 3. The crack pattern of cubes without and with fibres after testing is shown in Fig. 4.

      From Table-VII and Figs.-2 and 3 it is shown that the addition of binding wires as fibre significantly increase the compressive strength of concrete. It is also clear that with increase with the quantities of fibres the compressive strength of concrete is increasing.

      TABLE-VII VALUES OF AVERAGE COMPRESSIVE STRENGTH AND PERCENTAGE INCREASE FOR DIFFERENT QUANTITIES OF FIBRES

      Quantity of Fibre added (kg/m3)

      Average compressive strength (N/mm2)

      % Increase in compressive strength

      0

      30.21

      0.00

      5

      32.96

      9.10

      10

      35.158

      16.38

      15

      35.71

      18.21

      20

      36.701

      21.49

      25

      38.38

      27.04

      30

      40.62

      34.46

      45

      40

      Compressive Strength (N/mm2)

      Compressive Strength (N/mm2)

      35

      30

      25

      20

      15

      10

      5

      0

      0 10 20

      Fi quantities ( /m3)

      30 40

    2. Split Tensile Strength Test

      bre Kg

      Fig. 2. Variation of average compressive strength for different quantities of fibres.

      45

      Compressive Strength (N/mm2)

      Compressive Strength (N/mm2)

      40

      35

      30

      Split tensile test was carried out on cylinder specimens with and without fibres after 28 days curing according to IS: 5816- 1999. Table-VIII and Figs.5 and 6 shows the split tensile test results of specimens without and with different quantities of fibres as well as the percentage increase in split tensile strength using fibres are also given. The crack pattern of cylinders without and with fibres after testing is shown in Fig.7.

      25

      20

      15

      10

      5

      0

      5 10 15 20 25 30

      Fibre quantities (Kg/m3)

      Plain Concrete

      Fibre Reinforced Cooncrete

      The results shows that like compressive strength, with addition of binding wires as fibres increases the split tensile strength of concrete. It is also observed that plain concrete fails suddenly once the ultimate load carrying capacity exceeded on the other hand fibre reinforced concrete continues to sustain considerable loads even the loads exceeded the ultimate load.

      Fig. 3. Comparison of average compressive strength for different quantities of fibres with plain concrete.

      TABLE-VIII VALUES OF AVERAGE SPILT TENSILE STRENGTH AND PERCENTAGE INCREASE FOR DIFFERENT QUANTITIES OF FIBRES

      Quantity of Fibre added (kg/m3)

      Average Split tensile value

      % Increase in split tensile strength

      0

      3.41

      0

      5

      3.81

      11.73

      10

      4.23

      24.05

      15

      4.27

      25.22

      20

      4.32

      26.69

      25

      4.47

      31.09

      30

      4.59

      34.60

      5

      Split tensile strength (N/mm2)

      Split tensile strength (N/mm2)

      4.5

      4

      3.5

      3

      2.5

      2

      1.5

      1

      0.5

      0

      0 5 10 15 20 25 30

      Fibre quantities (Kg/m3 )

      1. Without fibres

        Fig. 5: Variation of average split tensile strength for different quantities of fibres.

        5

        4.5

        Split tensile strength (N/mm2)

        Split tensile strength (N/mm2)

        4

        3.5

        3

        2.5

        2

        1.5

        1

        0.5

        0

        5 10 15 20 25 30

        Fibre quantities (Kg/m3)

        Plain Concrete

        Fibre Reinforced Concrete

      2. With fibres

        Fig.7: Crack pattern of cylinders without and with fibres after testing.

    3. Flexural Strength Test

      Flexural strength was determined according to IS: 516-1999 for the beam specimens with and without fibres. Test results obtained from the flexural strength test carried out on the beam specimens with and without fibres are shown in Table- IX and Figs. 8 and 9.

      It can be seen from the flexural strength test results that addition of fibres can considerably increase the flexural strength of concrete. The bridging action of fibres keeps the

      Fig. 6. Comparison of average split tensile strength for different quantities of fibres with plain concrete.

      bond strength between fibre and concrete which prevent the sudden failure of concrete.

      TABLE-IX. VALUES OF AVERAGE FLEXURAL STRENGTH AND PERCENTAGE INCREASE FOR DIFFERENT QUANTITIES OF FIBRES

      Quantity of Fibre added (kg/m3)

      Average flexural strength value

      % Increase in Strength

      0

      2.82

      0

      10

      3.2

      13.48

      15

      3.37

      19.50

      20

      3.42

      21.28

      25

      3.54

      25.53

      4

      Flexural Strength (N/mm2)

      Flexural Strength (N/mm2)

      3.5

      3

      2.5

      2

      1.5

      1

      0.5

      0

      0 10 15 20 25

      Fibre quantities (Kg/m3 )

      1. Without fibres

        Flexural Strength (N/mm2)

        Flexural Strength (N/mm2)

        Fig.8. Variation of average compressive strength for different quantities of fibres.

        4

        3.5

        3

        2.5

        2 Plain concrete

        1.5 Fibre Reinforced

        1 Concrete

        0.5

        0

        10 15 20 25

        Fibre quantities (Kg/m3 )

        Fig. 9. Comparison of average flexural strength of beams for different quantities of fibres with plain concrete.

      2. With fibres

    Fig.10. Crack pattern of beams without and with fibres after testing.

    From the crack formation pattern of all specimens used for compressive, split tensile and flexural strength, it is also clear that with fibres the crack formation is very small compared to the non fibre specimens. Addition of binding wires as fibres, improve the ductility of the concrete along with its post cracking load carrying capacity.

  4. CONCLUSIONS

The result of the study shows that addition of binding wires improves the strength characteristics of concrete. It is also seen that with increase with the quantities of fibre, the compression, split tensile and flexural strength of concrete is increasing. But with increase with the quantities of fibres in concrete, impart extra load on the structure and also increase the cost. Apart from the strength characteristics, it is also clear from the results and the crack pattern of the tested specimens that addition of binding wires as fibre improve the ductility of the concrete along with its post cracking load carrying capacities.

REFERENCES

  1. Shah, Surendraand Rangan (1994), Effect of Fiber addition on concrete strength, Indian Concrete Journal.

  2. Vikrant S. Vairagade et al ., Introduction to Steel Fiber Reinforced Concrete on Engineering Performance of Concrete,International Journal of Scientific & Technology Research Volume 1, Issue 4, May 2012.

  3. IS: 456. 2000. Indian Standard Plain and Reinforced Concrete – Code of practice. Bureau of Indian Standards, New Delhi.

  4. IS: 516. 1959. Indian Standard Methods of Tests for Strength of Concrete- Code of practice. Bureau of Indian Standards, New Delhi.

  5. 10262. 1982. Indian Standard Recommended Guidelines for Concrete Mix Design- Code of practice. Bureau of Indian Standards, New Delhi.

  6. IS: 383. 1963. Indian Standard Specification for Coarse and Fine Aggregates from Natural Sources for Concrete- Code of practice. Bureau of Indian Standards, New Delhi.

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