Investigation into the effect of KWB and KB polymeric fibers of Sirjan Nano Yarn on mechanical properties of fine-grained concrete

Concrete is now widely used in civil engineering industry. Concrete structures have shown weak performance against tensile and bending forces, unlike their high compressive strength. To improve their bending and tensile behaviour, they are enforced by different materials such as fibers. In this paper, the impact of volume ratio of two polymeric fibers, namely Korta Wave Blend (KWB) and Korta Blend (KB) manufactured by Sirjan-nano Company, was statistically investigated on the mechanical properties of fine-grained concrete. Samples having 0, 0.5, 1, 1.5 and 2% volume ratio of each polymeric fibers were prepared and uniaxial compression, indirect tensile (Brazilian) and triaxial compression tests were carried out. Mechanical properties of mixtures including uniaxial compressive strength (UCS), Elastic modulus, tensile strength and triaxial compressive strength at different confining pressures were measured for each volume ratio. Using the results of triaxial compression tests, the cohesion and friction angle were calculated for each volume ratio. Results of uniaxial compression tests showed that the KWB fiber has lower impact on the increase in the UCS compared to that of KB fiber. The impact of increase in the KWB volume ratio on the Elastic modulus was not statistically significant while the increase in the KB volume ratio up to one percent resulted in a statistically significant increase in the Elastic modulus. Results of indirect tensile tests showed that the presence of KB fibers in the concrete results in a significant increase in the tensile strength. Based on the results of experiments and undertaken statistical analyses using analysis of variance, 1.5% and 2% volume ratios were selected as optimal ratio for KWB and KB fibers, respectively.