Abstract

 An experimental investigation has been carried out to assess the behavior of concrete beams blended with steel crimped fiber and flyash subjected to combined torsion-bending-shear with longitudinal reinforcement. The concrete is binary blended with 15% of fly ash by weight of cement as partial replacement of cement and addition of 0%, 0.5%, 0.75%, 1% of crimped steel fibers with aspect ratio of 80 are used for the study purpose. Compressive strength of concrete is measured by testing standard cubes (150mm x 150mm x 150mm) at the age of 28 days, the combined torsion-bending-shear strength is measured by testing beams of size 100x100mm and length 1200mm with a bracket attached at center of size 100x100x300mm.This bracket is adequately reinforced to avoid any failure at joint. The tests were conducted on 12 beams for varying percentages of steel fibers and studied for their behavior under combined torsion-bending-shear. The study involved the influence of fiber addition on the ultimate torsion-bending-shear strength of beams.Test results indicated that fibrous concrete beams exhibited improved overall performance with respect to corresponding non-fibrous beams. Flyash with steel fiber has shown considerable improvement in the compressive and torsion-bending-shear strength of concrete. From the test results it is observed that the concrete mix with 15% fly ash replacement of cement of M30 grade concrete mixture has shown maximum compressive strength of 47 MPa at 28 days. Concrete mixture with 15% fly ash replacement of cement along with 0.75% of crimped steel fibers has shown significant improvement in various properties at the age 0f 28 days indicated by 38% increase in compressive strength and 58% increase in the combined torsion-bending-shear strength of concrete. Hence binary blended crimped steel fiber reinforced concrete with 15% fly ash with 0.75 % steel fibers is a novel material having superior performance characteristics compared with conventional concrete.

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