Optimization of wheat straw ash for cement replacement in concrete using response surface methodology for enhanced sustainability

Abstract This research explores the utilization of wheat straw ash (WSA), an agricultural by-product enriched with amorphous silica, as a partial cement replacement in concrete production. The WSA content ranged from 4% to 16% by mass, with water-to-cement (w/c) ratios varying between 0.4 and 0.6. Using response surface methodology (RSM) combined with central composite design, this study optimized mix designs and developed predictive models for key performance indicators, including workability and mechanical properties of concrete. The results demonstrate that an optimal balance of the WSA and a reduced w/c ratio significantly enhance both the workability and mechanical performance of concrete. The pozzolanic reaction between WSA and calcium hydroxide promotes the formation of calcium silicate hydrate (C-S-H) gel. The optimal mix composition, comprising 10.12% w (WSA) with a w/c ratio of 0.45, achieved a desirability score of 71.83%. This ground-breaking research underscores the viability of WSA as a supplementary cementitious material, offering a sustainable solution for concrete production while simultaneously enhancing its workability and mechanical properties.