Wheat Straw Ash as a Sustainable Supplementary Cementitious Material in Concrete: Effects of Replacement Level, Physicochemical Characteristics, and Mechanical Performance

Abstract This study aims to critically evaluate the potential of wheat straw ash (WSA) as a sustainable supplementary cementitious material (SCM) for enhancing the mechanical performance of concrete while reducing Portland cement consumption and promoting agricultural waste valorization. The research systematically examines the influence of WSA replacement levels on compressive, splitting tensile, and flexural strengths, with particular emphasis on identifying the optimum replacement level and assessing the feasibility of relatively high WSA incorporation. A comparative synthesis of published literature is integrated with experimental observations to establish the consistency of reported strength trends across different WSA contents and processing conditions. The study further investigates the mechanisms governing strength development, particularly the contribution of silica-rich WSA to pozzolanic reactions and subsequent calcium silicate hydrate (C–S–H) formation. Particular attention is given to the effects of WSA physicochemical characteristics, including silica structure, particle fineness, combustion temperature, combustion duration, and post-processing, on pozzolanic reactivity and mechanical performance. The overall objective is to establish scientifically robust relationships between WSA characteristics, replacement level, and concrete strength development, thereby determining the conditions under which WSA can function effectively as an SCM. The findings are intended to support optimized WSA utilization and advance sustainable, low-carbon concrete production.