Abstract
Concrete is considered one of the most important building materials in all eras. One of the renowned items of concrete fabrication is ordinary Portland cement (OPC). In the production process of OPC, an immense quantity of CO2 gas is emitted. Consequently, local and trash materials are employed as partial substitutions for cement to construct eco-friendly concrete. In this research, the influence of using a combination of rice husk ash (RHA) and olive waste ash (OWA) at various proportions (i.e. 0 %, 5 %, 10 %, 15 %, 20 % and 25 % for RHA and 0 %, 2.5 %, 5 % and 7.5 % for OWA) as a partial replacement of cement on high-strength concrete is investigated. For this goal, 21 mixes are prepared. The fresh state properties are represented in slump values and mechanical properties, namely, compressive strength, splitting tensile strength, flexural strength, modulus of elasticity, and bond strength, where the compressive strength was evaluated at 7 days and 28 days while the other mechanical properties were evaluated at 28 days. Finally, the microstructure properties are evaluated. Results reveal that the optimum dosages for RHA and OWA are 20 % and 5 %, respectively. Using 20 % RHA with 5 % OWA increases compressive strength by approximately 58.7 %.