Mechanical properties of cement-based composites incorporating eco-friendly aggregate of waste rubber

The purpose of this study is to evaluate the waste tires that harm the environment as aggregate in concrete and to examine the effect on the mechanical properties of concrete. Three different classes (powder, crumb and chips) of waste rubber with seven different ratios (0%, 4%, 8%, 12%, 16%, 20% and 24%) and two different water to cement ratio (0.4 and 0.5) were used in concrete production. In this regard, this study conducted various experiments consisting of 28 and 90 days of the curing process to determine the properties of unit weight, compressive, flexural, and splitting tensile strength, along with ultrasonic pulse velocity (UPV) and dynamic modulus of elasticity. The waste rubber concrete with the highest compressive strength at the end of 90 days is the concrete that includes 4% waste rubber (0.4WR4) with 58.81 MPa. Concrete containing 8% waste rubber has the highest UPV of 5660 m/s after 90 days. The increase in the water/cement ratio from 0.4 to 0.5 and the waste rubber ratio cause deterioration in the mechanical properties of concrete. Although the use of waste rubbers does not bring an increase in strength, it is feasible to produce high strength concretes with 4% and 8% waste rubber substitution ratios. The water/cement ratio and curing time were highly effective on the mechanical properties of rubberized concrete.