Synergistic Effects of Silica Fume and Recycled Aggregate in M30 Concrete

Recycled concrete aggregate (RAC) can be utilized in structural concrete to reduce the environmental impact of waste concrete and the consumption of natural resources. The current study described the mechanical properties of concrete and evaluated the synergistic effects of recycled aggregate, likely at 100% content, with silica fume (SF) partially substituting for cement. The study's primary variables included the dosage of silica fume used as a partial replacement of ordinary Portland cement (OPC) at five different percentages: 0%, 4%, 8%, 12%, and 16% by weight. Five distinct mixtures, designated RACSF-0, RACSF-4, RACSF-8, RACSF-12, and RACSF-16, were made using differing concentrations of silica fume for M30 concrete. The slump test was used to determine how workable concrete mixes were. After increasing the proportion of SF, the test results showed a downward trend. The mechanical properties of RACSF were tested at 7 and 28 days after curing utilizing compressive and splitting tensile tests. The results showed that adding SF improved RACSF performance at both early and late curing ages, with the best results achieved at 12% SF addition. As a result, 12% SF is recommended as a partial substitute for cement in RAC.