Sustainable Utilization of Agricultural Waste Ashes in Concrete through Experimental Evaluation of Rice Husk Ash and Sawdust Ash as Partial Cement Replacements

Concrete remains the most widely used construction material worldwide, yet the production of its key component, cement, contributes significantly to global carbon emissions. This study investigates the potential of agricultural waste materials, specifically rice husk ash (RHA) and sawdust ash (SDA), as partial substitutes for cement in concrete production. Both ashes are rich in silica and possess pozzolanic properties that can enhance the mechanical performance of concrete while reducing environmental impact. M30 grade concrete mixes were prepared with RHA and SDA replacing cement at varying percentages (5%, 10%, 15%, 20%, and 25%), and combinations of RHA and SDA were also tested. A total of forty-two specimens were examined for compressive, flexural, and split tensile strengths after 7 and 28 days of curing. The results showed that RHA improved compressive strength up to a 10 percent replacement, while SDA performed optimally at 5 to 10 percent. Beyond these levels, a decline in strength was observed. The combined use of RHA and SDA also yielded satisfactory results within similar ranges. These findings indicate that limited incorporation of agricultural waste ashes can produce cost-effective, sustainable, and structurally reliable concrete suitable for modern construction needs.