Investigation on The effect of macro synthetic and steel fibers on stress strain and mechanical properties and durability of fiber reinforced concrete

Today, concrete is regarded as one of the main materials in the construction industry, but besides its advantages, it is brittle and fragile and its tensile strength is lower than compressive strength. Due to the development of science and technology, the use of metal, polymer, glass and natural fibers in the construction industry is considered as an effective step in eliminating the poor tensile strength of ordinary concrete. Thus, in this research, the effect of steel and macro synthetic fibers on the behavioral model of concrete and mechanical properties (compressive and tensile strength, modulus of elasticity) and durability (electrical resistance, water permeability of concrete) have been investigated. Hence, in this research, 10 mixing designs with three different types of fibers, including steel, macro synthetic, polyolefin, and polypropylene fibers with 0.5, 1, 1.5 vol% were tested, and the results show that the steel fibers have no considerable effect on the compressive strength at a percentage higher than 0.5 and significantly increase the tensile strength and reduce the electrical resistance. The macro synthetic fibers of polyolefin and polypropylene have insignificant effect on compressive strength and even reduced compressive strength at high percentages and have a positive effect on tensile strength, electrical resistance, and water permeability, and the fibers can be used to increase the area under the stress-strain curve.