Evaluating the mechanical properties of recycled aggregate concrete with variable coarse and fine aggregate replacements
Zia Ul Islam, Salman Farooq, Muhammad Shoaib, Muhammad Ishfaq, Tanveer Ahmad, Hasnain Ahmad
Abstract
Abstract This study examines the mechanical properties of Recycled Aggregate Concrete (RAC) in comparison to Normal Aggregate Concrete (NAC), focusing on the effects of varying fine and coarse aggregate replacement ratios. A consistent 1:2:4 mix ratio and a water-to-cement (w/c) ratio of 0.55 were used for all mixes. Ten concrete types with 50%, 75%, and 100% replacement of fine and coarse aggregates were tested for compressive strength (CS) and splitting tensile strength (TS) at 7-day and 28-day curing periods. The results show that at 50% coarse aggregate replacement, 28-day CS decreased by 8–12% and TS by 13–15% compared to NAC. At 100% replacement, CS decreased by 24–27% and TS by 21–23%. Full replacement of both fine and coarse aggregates resulted in the greatest reductions, with CS decreasing by 35–38% and TS by 30–32%. The novelty of this study lies in the evaluation of combined fine and coarse aggregate replacements, an area that has been less explored in the existing literature. These findings indicate that RAC, particularly at higher replacement levels, is better suited for non-structural or low-load-bearing applications such as pavement sub-bases, walkway slabs, partition walls, and low-strength concrete blocks. Due to the observed reduction in mechanical performance, caution is recommended when considering RAC for structural or high-strength applications.