EFFECT OF WHEAT STRAW ASH ON COMPRESSIVE STRENGTH AND WORKABILITY OF CONCRETE

Abstract

Concrete is the most widely used construction material globally, but its production relies heavily on Portland cement, contributing significantly to CO₂ emissions and creating a substantial environmental burden. Wheat straw ash (WSA), an abundant agricultural by-product with silica content and pozzolanic potential, presents a promising opportunity for partial cement replacement, offering both environmental and economic benefits. This study investigates the partial replacement of cement with WSA in concrete mixes, evaluating its effect on compressive strength and workability. Replacement levels were limited to 0%, 2%, 4%, and 6% by weight, as higher WSA contents require increased burning to produce sufficient ash, raising processing costs and offsetting the economic benefits of this substitution. Concrete specimens were cast at each replacement level and tested for compressive strength at 7 and 28 days. Results show a gradual decrease in compressive strength with increasing WSA content: at 28 days, the control mix (0% WSA) achieved 21.75 MPa, while the 2%, 4%, and 6% replacement levels achieved 19.5 MPa, 18.4 MPa, and 17.5 MPa, respectively. Workability, measured via slump test, also decreased with increasing WSA content, with slump values of 45 mm, 44 mm, 42 mm, and 38 mm for the 0%, 2%, 4%, and 6% replacement levels, respectively. Despite these reductions, the results suggest that partial replacement of cement with WSA up to 6% is technically and economically feasible, given the modest strength loss relative to the environmental and cost benefits gained. This approach offers reduced CO₂ emissions, recycling of agricultural waste, and acceptable mechanical performance for non-structural or moderate-load applications