Mechanical and durability properties of waste rubber fiber concrete with and without silica fume

Availability of natural sand conforming to required standards for use in concrete is diminishing day by day and is severely affecting the construction industry. On the other hand, disposal of used rubber tyres is an environmental, health and esthetic problem as its recycling is extremely difficult. In this paper, a systematic experimental investigation is carried out on concrete with rubber fibers (obtained by grinding waste rubber tyres) as partial replacement of fine aggregates, to evaluate the compressive strength, density, water permeability, static modulus of elasticity, dynamic modulus of elasticity and chloride diffusion. Rubber fibers have been used with three different water-cement ratios (0.35, 0.45 and 0.55). Six levels of rubber fibers contents (0, 5, 10, 15, 20 and 25%) as partial replacement of sand and three levels of silica fume (0, 5 and 10%) as partial replacement of cement have been considered. Microstructure analysis of rubber fiber sample by scanning electron microscope and Energy dispersive X-ray analyzer has been carried out. Compressive strength, static and dynamic modulus of elasticity of waste rubber tyre fiber concrete are found to decrease with the increase in the replacement level of fine aggregates by rubber fibers.