Eco-friendly concrete: Using fly ash and shredded corn cob ash as sustainable partial substitutes

Abstract

In this research seven concrete mixes were designed and prepared, of which one was a control mix (CC) and six were SCCA mixes (SCC1-SCC6). The fresh concrete characteristics were determined by slump and compaction factor tests, which indicated a progressive diminish in workability with an enrich in SCCA content due to the porous and irregular nature of corn cob ash. The density of concrete diminished from 2178 kg/m³ for CC to 1770 kg/m³ for SCC6. The results of mechanical tests indicated that the compressive, split tensile, and flexural strengths of concrete diminished with an enrich in SCCA content, with SCC6 showing a diminish of about 22%, 22.5%, and 18% at 28 days, respectively. The saturated water absorption and acid resistance tests indicated a marginal enrich in permeability and susceptibility with an enrich in SCCA content. Strength and durability trends were explained by SEM analysis, which showed that fly ash boosted matrix densification while excessive SCCA produced void formation and weak interfacial transition zones. Overall, the study shows that substituting 15% fly ash for 4–12% SCCA achieves the best possible balance between durability, mechanical performance, offering a practical way to produce environmentally friendly concrete using agricultural waste.