Laboratory optimization and environmental investigation of rubber concrete in case of simultaneous use of rubber powder and rubber fibers

Annually, thousands of tons of rubber tires are producedconsumed, and disposed in Iran.In the past decade, researchers have conducted numerous investigations on the utilization of rubber fibers or rubber granules in concrete and their effects on its mechanical properties. Howeverthe concurrent use of these two materials in lieu of sand and gravel in concrete has not been thoroughly examined.This study explores the effects of simultaneously incorporating these two materials on the mechanical characteristics of rubberized concrete and investigates the environmental implications of rubber utilization in concrete.By examining the results of slump tests conducted on rubberized concrete specimens with water-to-cement ratios of 0.45, 0.50,and 0.55, and incorporating rubber granules and rubber fibers up to 25%, it was observed that the slump exhibited a decreasing trend from 31 to 82 millimeters. Test results indicated a reduction in compressive strength with increasing rubber content. Specifically,13% of the combination of rubber granules and fibers led to a reduction of around 50% in the compressive strength of rubberized concrete compared to the control sample. In the case of a water-to-cement ratio of 0.55, as the rubber granules and fibers were increased from 4 to 25%, compressive strength decreased from 15.78 to 3.19 MPa.Using different water-to-cement ratios and varying percentages of rubberized concrete in the software SimaPro, it was determined that the combination of rubber granules and fibers resulted in an approximate 40% reduction in carbon dioxide gas emissions in the environment.The optimum condition across all ratios was achieved by incorporating 4% rubber granules and fibers.