Effect of recycled coarse aggregate on physical and mechanical properties of concrete

Recycling of building waste has become essential process in the construction industry due to the sustainability and economic benefits such as decreasing the waste to landfill, conserving natural resources, and reducing pollution. Large amount of building waste is produced from the construction and demolition process of reinforced concrete (RC) structures. In this paper, the effect of using recycled coarse aggregate (RCA) on the behavior of concrete is experimentally studied. The RCA is prepared by crushing and sieving of waste of standard compression test cubes having a compressive strength ranging between 25 MPa and 30 MPa. The physical and mechanical properties of RCA are experimentally estimated and compared to those of natural coarse aggregate (NCA). A set of 72 standard concrete cubes, cylinders, and beams specimens are made using coarse aggregate replacement ratios (CARR) of 0%, 30%, 50%, and 100%. The specimens are tested to estimate the compressive, splitting, and flexure strengthens at the ages of 7 and 28 days. The study is extended by using the RCA in casting 12 RC columns with CARR similar to those of specimens. The columns are tested in an axial compression test protocol till failure. Crack patterns, failure loads, strains, displacements, and toughness of the tested columns are compared. It is concluded that using a CARR of 30% and 50% and a specific water cement ratio provides better mechanical behavior than that of NCA while the CARR of 100% yields worst mechanical behavior compared to that of NCA.