Triangular Polyestor Fibers as Secondary Reinforcement in Concrete for Flexure / Split Tensile Strength

Transcription

1 Triangular Polyestor Fibers as Secondary Reinforcement in Concrete for Flexure / Split Tensile Strength KRS. Narayan, BE.Civil, M.Tech Leeds University - U.K., F.ICI., F.ACCE "Fiber Reinforced Concrete" is relatively a new construction material developed through extensive research and development work during the last two decades. Fiber Reinforced Concrete (FRC) is defined as composite material which consists of conventional reinforced by randomly dispersed short length fibers of specific geometry, made of steel, synthetic (polymeric) or natural fibers. Plain cement has very low tensile strength and causes formation of micro cracks in stressed and unstressed states of. Also, it has a low strain at fracture and brittleness with less ductility especially in case of High Performance Concrete. Fiber Reinforced Concrete is the answer to modify these properties of Plain Concrete. Advantages of Frc Various advantages of Fiber Reinforced Concrete are, - Resistance to Micro-Cracking. - Toughness and Post-Failure Ductility - Impact & Abrasion Resistances. - Resistance to fatigue. - Improved strength in shear, tension, flexure and compression. - Reduced permeability The interaction between the Fiber and Concrete matrix is the fundamental property that affects the performance of a cement based fiber composite materials. An understanding of this interaction is needed for forecasting the fiber contribution and for predicting the behavior of such composites. The following are the major parameters affecting the fiber interaction with the matrix. - Condition of the matrix--uncracked or Cracked. - Matrix composition. - Geometry of the Fiber-Triangular or Circular. - Type of fiber--steel, polymeric, mineral or naturally occurring fiber. - Surface characteristics of the fiber. - Stiffness of the fiber in composition with matrix stiffness. - Orientation of the fibers--aligned versus random distribution. - Volume fraction of fibers. - Rate of loading. - Durability of fiber in the composite and the long term effect in the Concrete matrix. Experimental Investigation The behaviour and strength of Conventional and Fiber Reinforced Concrete are ascertained by testing the specimens in the laboratory. This chapter deals with the mix design, preparation of the specimen, and casting, testing and test results of the specimens. Materials It is necessary to get the maximum performance out of all of the material involved in producing a. The materials involved in this project are Portland cement, coarse aggregate, fine aggregate and super plasticizers. The additional material involved in this project is Triangular Polyestor Fiber-Synthetic Fiber. Cement The cement used for this investigation was OPC5 grade Birla cement. The specific gravity of the cement was found 68 The Masterbuilder - November 0

2 to be. and it is conforming to IS Fine Aggregate The fine aggregate used for all the specimens was complying with IS The specific gravity of fine aggregate was.5, sieve analyses were conducted and it was found that the sand used was conforming to zone II grading. The fineness modulus of fine aggregate was.074 Coarse Aggregate The coarse aggregate used was hard broken stone drawn from an approved quarry. Mean size of 0mm was used. The specific gravity of coarse aggregate was.7. And it was confirming to IS Water Portable water available in the laboratory was used for casting all the specimens in this investigation. The quality of water was found to satisfy the requirements of IS Synthetic Fiber (Triangular Polyestor Fiber) The fiber used is a mm long VIRGIN TRIANGULAR MONOFILAMENT Polyestor, with an Aspect Ratio of < 60. For a mean sized aggregate of 0mm, mm Fiber length is adequate. Young's Modulus of Triangular Polyester Fiber was found to be >6500MPa Super Plasticizer 4 Material Cement OPC -5 grade Fine aggregatesand Course aggregates- 0mm size Fibers-- Triangular Polyestor Fiber Name of the property Fineness of cement Initial setting time Standard consistency Final setting time Grading Water absorption Fineness modulus Water absorption Length (mm) Crossection Aspect ratio Diameter Density Experimental results.06 8% 4 min % 65 min.5 II % % mm Triangular mm 0.90 Kgs / Cu.M The mix proportion adopted for is :.8:.97 with w/c ratio of 0.4 for a desired Slump of 75mm + - 5mm. All the samples are prepared from the desired mix. The volume of fiber added is 0.5% of weight of cement. Concrete Mixer was of 0. Cu.M batch capacity and to prepare a Concrete with a Slump of 75mm + - 5mm, 40Kgs C/c has been considered after sufficient Trial mix preparations. Details of mix Testing Procedure Commercially available super plasticizer having a specific gravity of. at 5 degree centigrade. Desired Slump was 75mm + - 5mm for better workability. Material Properties Material Cement 5grade OPC Fine aggregate Quantity per m in kg Mix Design In this study, Indian standard recommended method (IS 06-98) has been adopted for the mix design Coarse aggregate (0mm size) Water Fiber Super plasticizer % by weight of cement 0.4% by weight of cement - Cube Compressive Strength The test was conducted as per IS The cube of standard size 50 mm x 50 mm x 50 mm were used to find the compressive strength of specimen after 8 days curing, and were placed at the compressive testing machine of capacity of 00 tons with out eccentricity. At failure, the maximum load was noted and compressive strength was calculated. The average of three values is taken as the compressive strength. - Cylinder Compressive Strength The specimens used for the test were of 50 mm diameter The Masterbuilder - November 0 69

3 and the height of 00 mm. Tests were conducted using compressive testing machine of 00 tones. The test was carried out at a uniform stress after the specimen had been centered in the testing machine. Flexural Strength Test Set up Compressive Strength Test Set Up - Split Tensile Strength Test The test was conducted as per IS The test was carried out by placing the cylindrical specimen of diameter 50 mm and height 00 mm, horizontally between the loading surface of a compressive testing machine and the load was applied until failure of the cylinder along the vertical diameter. The maximum load applied was noted down. - Flexural Test The test was conducted as per IS Beams of size 00 x 00 x 500 mm were used for the determination of flexural strength. The test was conducted using the universal testing machine adopting two points loading. The specimen was positioned in the testing machine and a steel I section beam for transferring the concentrated load as the two point load (/ each other) was kept over the beam. The supporting length of the prisms was fixed at 400 mm and load was applied Up to final failure of the specimen. - Young's Modulus Of Concrete Cylinder The test was conducted using compressometer as per IS The cylinder of standard size 00 mm height and 50 mm dia were used to find the modulus of elasticity. Specimens were placed on UTM of 00 tons capacity without eccentricity and uniform load was applied till the target load failure of the cylinder. The target load and deflection were noted and modulus of elasticity was obtained. The original length of the compressometer is 50mm. The deflection readings are change in length, from that the strain was calculated For finding young's modulus of, the deformation of various loads was observed and the results are plotted graphically against the stress. Using the stress strain curve tangent in drawn and modulus of elasticity is found. Compressive Strength Test Set Up (Stress- Strain Relationship Test Arrangement) Test Results Split Tensile Strength The cylinder specimens are cast and tested for split tensile strength as per IS using compression testing machine of capacity 00 tons. Flexural Strength This test was conducted as per IS on prisms of standard size 00x00x500 mm. Tests were carried out in Universal Testing machine. The supporting length of the prisms was fixed at 400mm with two points loading at / rd distance with each other. Two uniform point loads were Loaded Area (mm ) Ultimate Crushing Load (KN) Split tensile Strength (N/mm ) Strength (N/mm ) Fiber (F) The Masterbuilder - November 0

4 Ultimate Crushing Load (KN) Flexural Strength (N/mm ) Average flexural Strength (N/mm ) Fiber (F) Loaded Area (mm ) Ultimate Crushing Load (KN) Compressive Strength (N/mm ) Strength (N/mm ) Fiber (F) 50x50 50x Compressive Strength of Cube Loaded Area (mm ) Ultimate Crushing Load (KN) Compressive Strength (N/mm ) Strength (N/mm ) Fiber (F) Compressive Strength of Cylinder applied and the maximum failure load was noted. The modulus of rupture was calculated. Compressive Strength The cube and cylinder specimens are tested for compressive strength using compression testing machine of capacity 00 tones Young's modulus (N/mm ) N N N F F F Average (N/mm ) Modulus Of Elasticity (Or) Young's Modulus Of Concrete The cylinder specimen is casted and tested for young's modulus, using UTM of capacity of 00 tons. Comparison of Results and Discussions Test results of the specimens are compared and the discussion is made from the test results. The fibers are compared with the conventional. Split Tensile Strength The split tensile strength is increased by 0.% for Triangular Polyestor Fibre reinforced over plain. Flexural Strength The flexural tensile strength is increased by7.9% for Normal Fiber Strength (N/mm ) Increase in Compressive Strength (N/mm ) 0. Triangular Polyestor Fibre reinforced over plain. Young's Modulus of Cylinder Specimen The young's modulus is increased by 4.8% for Triangular Polyestor Fibre reinforced over plain. Comparison of Young's Modulus Conclusion - Addition of Triangular Polyestor Fiber in Concrete 7 The Masterbuilder - November 0

5 Normal Fiber Average flexural Strength (N/mm ) Increase in flexural Strength (N/mm ) 7.86 increases the Split Tensile Strength at 8 days by 0.% at a fiber dosage of 0.5% by weight of cement. - Due to addition of Triangular Polyestor Fiber, the Flexural Strength is increased by 7.86% compared with Conventional Concrete. Normal Fiber Average % of increase The Young's modulus of FRC is increased slightly when compared with Conventional. This is due to the contribution of young's modulus of Fiber in Concrete. - Stress-Strain Curve for Cylinder specimens-normal V/s Fiber Concrete. Fig - Specimen Stress strain curve for cylinder specimen - Fiber References Fig - Specimen - Dr.A.R.Santha Kumar-Emeritus Professor-IIT-Madras and Former Dean-Anna University. - Mr.Johnson and Mr.Kanaga Sabapathy-Project In partial fulfillment of the requirements for their M.E-Degree. - Asad Esmaily and Yan Xiao. "Behaviour of reinforced column under variable axial loads". ACI structural journal, sept - oct Balasubramanian.K, Bharat kumar.b.h, Gopalakrishnan.S and Paremeswaran.V.S. "Flexural behaviour of steel fiber reinforced beams under static load". Journal of structural engg, vol.5.no., oct-998,pg Barr.B, Asghari.A and Hughes.T.G, "Tensile strength and toughness of FRC materials".the international journals of cement composite and light weight. Vol 0, no. Pg 0-07 Fig - Specimen Stress strain curve for cylinder specimen - normal - Baskar.S, Leung.C, Li.V.C,Wang Y and Yamanobe.K " Tensile flexure mechanism and mechanical and properties of fiber reinforced ".Proceddings of the international symposium The Masterbuilder - November 0 7

6 on fibre reinforced Dec 6-9, 987 Madras, India pg Evan.c Bendz and Sean bukley. "Repeating a classic set of experiments on size effect in shear of members without stirrups". ACI structural journal Nov - dec Graig.c.Ball, Bailey.E, Landers and Hooks.j "Flexural fatigue strength of steel fiber reinforced beams". ACI journal Nov 97 pg Kaushik.S.K, Gupta.V.K, Tarafdar, "Behaviour of fibre reinforced beams in shear". The international symposium on fiber reinforced.dec 6-9, 987, Madras, India pg Krishna Raju.N, Basavarajaiah,B.S, and Janardhan Rao.K. "Compresive strength and bearing stress of steel fibre reinforced " ICJ, vol 5, june977, pg Nataraja.M.C, Dhang.N and Guota "Steel fibre reinforced under compression". ICJ vol 70 July 998 pg Paremeswaren.V.S, "Research and application of FRC in Indian scenerio". ICJ, vol 70 oct 996,pg Swamy R.N, AL-Tann.S.A and Ali.S.A.R. "Deformation and ultimate strength in flexure of reinforced beams made with steel fibrous " ICJ, vol 78, Sep - Oct 98, pg Shetty M.S "Concrete technology theory and pratice (First edition 98) Publisher, S.chand and company. New Delhi. - Bansal.R.K. "A text book of strength of materials (Third edition 996) publisher lakshmi publications (p) Ltd.New Delhi. - I.S: "Indian code for recommended for guidelines for mix design" - I.S: 86-Part--96 "Indian standard methods of test for aggregate for " - I.S: "Indian code for method of testing for strength of " - I.S: "Indian code for publication for plain and reinforced (fourth revision)". - I.S "Indian code for method of testing for split tensile strength of cylinders". 74 The Masterbuilder - November 0