ADVANCES in NATURAL and APPLIED SCIENCES

Transcription

1 ADVANCES in NATURAL and APPLIED SCIENCES ISSN: Published BY AENSI Publication EISSN: January 10(1): pages Open Access Journal Experimental Study on Flexural and Shear Behaviour of Fibre Reinforced Concrete Beams 1 Karthik M.P., 2 Dr. Sreevidya V., 3 Dr. Robert Ravi and 4 M. Gowtham Raj 1 Asst. Prof. Pre final year Student SSM Institute of Engineering and Technology, Dindigul, Tamilnadu, India 2 Associate Professor, Sri Krishna College of Technology, Coimbatore, Tamilnadu, India. 3.4 Prof., Pre final year Student SSM Institute of Engineering and Technology, Dindigul, Tamilnadu, Received 12 January 2016; Accepted 28 February 2016; Available 4 April 2016 Address For Correspondence: Karthik M.P., Asst. Prof. Pre final year Student SSM Institute of Engineering and Technology, Dindigul, Tamilnadu, India mpandian.karthik@gmail.com Copyright 2016 by authors and American-Eurasian Network for Scientific Information (AENSI Publication). This work is licensed under the Creative Commons Attribution International License (CC BY). ABSTRACT This experimental investigation is focus on finding the flexural and shear behaviour of various Fibre Reinforced Concrete (FRC). The fibres used in the investigations are Steel fibre, Recycled Polyethylene Terephthalate fibre (RPET) and Polypropylene (PP) fibre, in the volume fraction of 0.5% of the concrete. And it was compared to the nominal mix of M40 grade of concrete as per IS 10262:2009. Fibres are usually used in concrete to control cracking due to both plastic and drying shrinkage. The mechanical properties of fresh and harden concrete was studied earlier, in that the Polypropylene fibre concrete had good in workability and steel fibrous concrete achieve % strength than the ordinary concrete. Totally three samples were tested for mechanical properties and two samples were tested for flexural and shear beams. The beams were subsequently loaded to failure by two point loading, different modes of failure and the ultimate strength and deflections were observed. The results show that the Steel and Polypropylene fibres were generally contributed towards bridging action and it achieves the maximum strength comparing with the control mix. The RPET fibre is comparatively lower than the other fibre. KEYWORDS: Fibre Reinforced Concrete, Steel, Recycled Polyethylene Terephthalate, Polypropylene fibre, Mechanical, Shear and Flexural behaviour, bridging action and maximum strength. INTRODUCTION Fibre Reinforced Concrete: Concrete is the most widely used construction material in the world due to its high compressive strength, long service life, and low cost. However, concrete has inherent disadvantages of low tensile strength and crack resistance. To improve such weaknesses of the material, numerous studies on fiber reinforced have been performed Sung Bae Kim et al [12]. The research results show that concrete reinforced with steel fibres significantly improves the performance of concrete and the polyethylene refutes its disadvantages such as workability, tensile and shear strength. One of the most important functions of steel fibres in concrete is the ability to transfer stresses across the cracked section, providing to concrete a residual strength, which magnitude depends on the fibre, matrix and fibre matrix properties Yining Ding et al [14]. Addition of randomly distributed fibers (steel, synthetic) drastically improves the performance of concrete and negates its disadvantages such as low tensile strength, low ductility, low energy absorption capacity and high shrinkage cracking etc., which depends upon fiber type, size, aspect ratio and volume fractions of the fibers used. Flexural and Shear behaviour: To Cite This Article: Karthik M.P., Dr. Sreevidya V., Dr. Robert Ravi and M. Gowtham Raj., Experimental Study on Flexural and Shear Behaviour of Fibre Reinforced Concrete Beams, Advances in Natural and Applied Sciences. 10(1); Pages: 57-64

2 58 Karthik M.P. et al., 2016/ Advances in Natural and Applied Sciences. 10(1) January 2016, Pages: In fact, fibres do not significantly increase the ultimate moment of RC members and, with rather tough FRC and low strain-hardening ratio of the longitudinal rebars, the rotation capacity can substantially decrease owing to a cracking localization at ultimate limit state and reinforcement of concrete with randomly distributed short fibers may improve the toughness of cementitious matrices by preventing or controlling the initiation, propagation, or coalescence of cracks Alberto Meda et al. The flexural behavior include cracking, failure pattern, deflection, ductility, and flexural strength have been studied. A prediction model for the flexural strength and deflection of ultra-high strength concrete beams under bending conditions has been proposed Abdoullah Namdar et al [2].The effect on crack opening and on tensile stress in the stirrups, with the prospect of a possible reduction in the amount of shear reinforcement. Reducing the number of shear bars in reinforced concrete elements may improve the production process. However, the relevance of this alternative is intimately linked to its capacity to avoid brittle failure under shear forces Youcef Fritih et al [15]. Sometimes the shear reinforcement may be less than sufficient if the loading configuration were different from that predicted during design, such as during earthquake or at critical section reinforcement conjunctions by Chalioris C.E and Sfiri E.F [3]. Fibres are effective shear reinforcement, its increased shear strength and ultimately results in ductile flexure failures, Hai H. Dinh et al [4]. Material and Methodology: A.Materials used Cement: The Portland Pozzolona Cement of 53 Grade conforming to IS 1489 (Part 1): [10] was used in this study. The specific gravity, initial and final setting of PPC 53 grade were 3.15, 30 and 600 minutes respectively. Fine Aggregate: Locally available river sand conforming to grading zone II of IS 383 [6]. Sand passing through IS 4.75mm Sieve will be used with the specific gravity of Coarse Aggregate: Locally available blue metal was used. Crushed granite stones of size passing through 20 mm sieve and retained on 10 mm sieve as per IS: 383-[6] was used for experimental purpose. Water: Ordinary portable water without acidity and alkanet available in pump as per IS 456: [7]. Super Plasticizer: Conplast SP 430 is used to reduce the frictional properties of concrete. Fibre: Steel Fibre: Crimped steel fibre was used. The properties of the fibre were tabulated below. Polypropylene Fibre: The polypropylene fibers have good ductility, fineness, and dispersion so they can restrain the plastic cracks, Singh S. P. et al [11]. Therefore, proper mixture of these two complementary fibers can make better mechanical properties of concrete. The diameter of monofilament fibers is elastic modulus is 5.88 GPa, and the tensile strength is 320 MPa. Polyethylene terephthalate Fibre: Polyethylene terephthalate (PET) is one of the most important and extensively used plastics in the world, especially for manufacturing beverage containers Sung Bae Kim et al [12]. It can provide crack control and ductility enhancement for quasi-brittle concrete as well as mass consumption alternative which is an important issue in the merit of recycling wasted materials. Table 1: Properties of Fibres. Properties Steel RPET PP Specific Gravity Length 50 mm 38 mm 38 mm Diameter 1 mm 0.02 mm 0.1 mm Aspect Ratio Table 2: Mix Proportion.

3 59 Karthik M.P. et al., 2016/ Advances in Natural and Applied Sciences. 10(1) January 2016, Pages: CEMENT F.A C.A WATER S.P 429 kg/m kg/m kg/m lit/m lit/m Fig. 1: Steel. Fig. 2: RPET. Fig. 3: PP Fibre. Table 3: Mix Design of FRC. Steel PET Cement F.A C.A Water S.P Specimens Fibre Fibre PP Fibre ( kg ) ( kg ) ( kg ) ( lit ) ( lit/m 3 ) ( kg ) ( kg ) ( kg ) Control Mix * * * * * * * * * FRC * * * * * * FRC * * * 0.4 * * * FRC * * * * * * 0.27 B.Methodology: Fig. 4: Methodology. Casting: Mechanical Properties: Specimens for Compressive strength, Split Tensile strength and Flexural strength are cast with cast standard mould size 150mm x 150mm x 150mm, 150mm x 300mm and 100mm x 100mm x 500mm respectively. In each test, 3 samples were casted for each test. Flexural and shear behaviour:

4 60 Karthik M.P. et al., 2016/ Advances in Natural and Applied Sciences. 10(1) January 2016, Pages: The design of flexural beam consist of main reinforcement 2 numbers of 10mm bars at bottom and 2 numbers of 8mm at top with a clear cover of 25mm. The shear reinforcement includes stirrups of 6mm bars at 125mm c/c spacing, shown in fig. 5. Design of the RCC beam for shear failure was done for span of 1.5m with partial shear reinforcements, 0.10m overhang was provided on the either side of the beam to accommodate for sufficient anchorage length. The main reinforcement provided were 12mm bars of 2 no s at bottom and the top shown in fig.6 Sunilaa George et al [13]. Fig. 5: Flexural Beam. Fig. 6: Shear Beam. Curing: For the mechanical property of concrete totally thirty six specimens were casted, for the flexural and shear behaviour of the beam two specimens were casted for each mix totally sixteen no of beams were casted. The casted specimens were cured in water for 28 days in the room temperature. A.Mechanical Properties: RESULTS AND DISCUSSIONS Table 4: Fresh Concrete. Mix Slump (mm) Control mix 68 FRC FRC FRC-3 72 Fig. 7: Slump on Fresh concrete. Table 5: Harden Concrete. SL. SPECIMEN SAMPLES NO. OF COMPRESSIVE TENSILE FLEXURAL

5 61 Karthik M.P. et al., 2016/ Advances in Natural and Applied Sciences. 10(1) January 2016, Pages: No 1 CONTROL MIX 2 FRC FRC FRC - 3 CURING DAYS STRENGTH (MPa) STRENGTH (MPa) STRENGTH (MPa) Fig. 8: Compressive strength. Fig. 9: Tensile strength. Fig. 10: Flexural strength. Table 6: Flexural and Shear Behaviour. Sl. Flexural Beam - Deflection Shear Beam - Deflection Load No Control mix FRC 1 FRC 2 FRC 3 Control mix FRC 1 FRC 2 FRC

6 62 Karthik M.P. et al., 2016/ Advances in Natural and Applied Sciences. 10(1) January 2016, Pages: Fig. 11: Flexural and Shear behaviour on Reinforced concrete Beams. Fig. 12: Flexural Failure. Fig. 13: Shear Failure. Table 7: Modes of Failure. Parameters Flexural Beams Shear Beam C B FRC 1 FRC 2 FRC 3 C B FRC 1 FRC 2 FRC 3 Initial Crack Ultimate Load Ultimate Deflection Mode of Failure Diagonal Diagonal Diagonal Diagonal Diagonal Shear Shear Shear Tension Tension Tension Tension Tension Failure Failure Failure

7 63 Karthik M.P. et al., 2016/ Advances in Natural and Applied Sciences. 10(1) January 2016, Pages: Fig. 14: Initial crack. Fig. 15: Ultimate Load. Fig. 16: Ultimate Deflection. Discussion: PET-filled concrete blends show a decrease in compressive strength, splitting tensile strength and modulus of elasticity. In other words, the inclusion of PET implies defects in the internal structure of the concrete, producing a reduction in strength and a decrease in stiffness. FRC can modify the collapse mode of beams moving the failure from concrete crushing to steel rupture. With this regard, high Fibre contents can determine a lower ductility as they lead to an early strain concentration in the rebars. Studies have shown that shear force is resisted by the combined action of three factors namely, the uncracked concrete in compression region, the aggregate interlocking and the shear acting across the longitudinal steel bars. The shear force across the steel bars is also known as dowel force. Conclusion: The better workability of fresh concrete was obtained in the Steel and PP Fibre reinforced concrete. The FRC-1 containing Steel fibres is 17%, 13% and 15% higher than the control mix of compressive, tensile and flexural strength respectively, likewise FRC-1 is 15%, 5% and 6% higher than the FRC-2 of compressive, tensile and flexural strength respectively. While comparing with the PET fibre FRC-3, the control mix is getting optimum strength, because of the balling effect of the fibre get shrinkage while hardening and reduce the strengthern property of concrete. Fibers significantly enhance the behavior at service conditions by increasing the stiffness in the cracked-stage and, therefore, by limiting the crack openings and deformations. A clear relation between beam behavior at service load and Fibre content was observed. This emphasizes the importance of FRC in improving the service life of RC structural elements. The shear behaviour show that increasing the side concrete cover to stirrup leads to wider diagonal crack spacing and partial absence of shear crack opening control at the surface of the elements. Diagonal cracking in shear beam mainly noted the main reason causing the difference in crack opening displacements at the same stirrup strain. The increase in diagonal crack spacing can be explained by the increase of concrete area around the stirrup in the case of large side to the stirrup.

8 64 Karthik M.P. et al., 2016/ Advances in Natural and Applied Sciences. 10(1) January 2016, Pages: REFERENCE 1. Alberto Meda, Fausto Minelli, Giovanni A. Plizzari, Flexural behavior of RC beams in Fiber reinforced concrete, Composites: part B 43- Science Direct Elsevier. 2. Abdoullah Namdar, Ideris Bin Zakaria, Azimah Bt Hazeli, Sayed Javid Azimi and Abdul Syukor Bin Abd. Razak, An experimental study on flexural strength enhancement of concrete by means of small steel fibers, Frattura ed Integrità Strutturale, 26: Chalioris, C.E. and E.F. Sfiri, Shear performance of steel fibrous concrete beams, Procedia Engineering, Elsevier Journals Ltd., 14: Hai, H., Dinh, Gustavo J. Parra-Montesinos, and James K. Wight, Shear behavior of steel fiberreinforced concrete beams without stirrup reinforcement ACI Structural Journal, 107(5): IS Specification for Coarse and fine aggregates from Natural sources for concrete, Bureau of Indian Standards. 6. IS , "Plain and Reinforced Concrete-Code of Practice", Bureau of Indian Standards,(BIS 2000). Fifth Reprint. 7. IS "Methods of tests for strength of concrete", Bureau of Indian Standards. 8. IS Methods of Sampling and Analysis of Concrete Bureau of Indian Standards. 9. IS 1489 (Part-1)-1991, Portland Pozzolana Cement-Specification, Bureau of Indian Standards. 10. IS , "Concrete Mix Proportioning-Guidelines", Bureau of Indian Standards,(BIS 2009), First Revision. 11. Singh S.P., A.P. Singh and V. Bajaj, Strength and flexural toughness of concrete reinforced with Steel Polypropylene hybrid fibres Building and Housing, Asian Journal of Civil Engineering, 11(4): Sung Bae Kim, Na Hyun Yi, Hyun Young Kim, Jang-Ho Jay Kim and Young Chul Song, Material and structural performance evaluation of recycled pet fiber reinforced concrete Cement and concrete composites, Elsevier Journals Ltd., 32: Sunilaa George, R., Thenmozhi and P.N. Magudeswaran, Experimental study on shear behaviour of activated fly ash concrete beams, Journals of Structural Engineering, 37(6): Yining Ding, Fasheng Zhang, Fernando Torgal and Yulin Zhang, Shear behaviour of steel fibre reinforced self-consolidating concrete beams based on the modified compression field theory Composite Structures, Elsevier Journals Ltd., 94: Youcef Fritih, Thierry Vidal, Anaclet Turatsinze and Gérard Pons, Flexural and Shear Behavior of Steel Fiber Reinforced SCC Beams Structural Engineering KSCE Journal of Civil Engineering, 17(6):