Use Of Coconut Fibers In High Strength Concrete For Improving Ductility

Abstract

Now a days concrete with enhanced properties such as high strength, toughness and durability is an essential demand of construction industry. High strength concrete (HSC) have enhanced mechanical properties than normal strength concrete (NSC). HSC has a variety of applications in construction industry such as high rise buildings, long span bridges and hydraulic structures. The factor which limits the utilization of HSC is its brittleness which is more than NSC. Therefore, controlling the brittleness of HSC is an important aspect in civil engineering construction industry which needs to be investigated. The mechanical properties of HSC can be improved by addition of fibers. As compared to artificial fibers, natural fibers are cheap and locally available. Among the natural fibers, coconut fibers have the highest toughness. In this study, mechanical properties of coconut fiber reinforced high strength concrete (CFR-HSC) are investigated. The effectiveness of coconut fibers (CF) in HSC is determined by comparing the mechanical properties of CFR-HSC with that of HSC having the same mix design. The properties of HSC are taken as a reference. The influence of 25 mm, 50 mm and 75 mm long fibers and 0.5%, 1%, 1.5% and 2% contents, by mass of cement are investigated. The microstructure of CFR-HSC is studied using scanning electron microscopy (SEM). The experimental results reveal that CFR-HSC show improved compressive, splitting-tensile and flexural strengths, strain ductility, energies absorbed and toughness indices than that of HSC. As compared to HSC, CFR-HSC showed enhanced post-cracking behavior which results in controlling the brittleness and ultimately improved the ductility. The overall best results are obtained for CFR-HSC having 50 mm long fibers and 1.5% fiber content. Thus, CFR-HSC with optimized length and content can be used for civil engineering structures. Keywords: High strength concrete; coconut fiber; mechanical properties; strain ductility; microstructure.