Effect of crushed concrete waste's maximum size as partial replacement of natural coarse aggregate on the mechanical and durability properties of concrete

The purpose of this research is to investigate the effect of the incorporation ratio of various maximum sizes of crushed concrete waste (CCW) on the mechanical and durability characteristics of concrete mixes. CCW is undoubtedly one of the main focuses of researchers in the field of sustainable development. However, knowledge regarding the effect of its maximum size on concrete is very scarce. For that purpose, 10 concrete mixes with three different ranges of CCW sizes (5-25 mm), (5-20 mm) and (5-12.5 mm) and different ratios of CCW (0%, 25%, 50%, 75%, and 100%) as replacement of natural coarse aggregate (NCA) were prepared. In addition, compressive and splitting tensile strength, freeze-thaw, water absorption, and abrasion resistance tests were made with the concrete mixes. Since one of the most relevant parts of any experimental investigation is to produce a mathematical relationship between the parameters studied, a statistical analysis was performed, specifically to understand the global effect of the various maximum sizes of CCW as partial replacement of NCA on various characteristics of concrete. The results show that, by incorporating 25% of CCW, the strength of concrete mixes improved for all sizes of CCW. In most cases, for the same incorporation ratio of CCW, the strength and durability (except for abrasion) of concrete slightly improved by decreasing the maximum size of the aggregates. Additionally, the resistance to freeze-thaw cycles results revealed that using CCW instead of NCA can improve the durability characteristics of concrete.