Performance evaluation of sandcrete blocks incorporating corn cob ash and coconut shell ash as partial cement replacements

The economic and environmental problems linked with cement manufacture are critical challenges faced by the construction industry. Therefore, there is a need to develop and apply approaches that will promote the sustainability of cement-based materials. This study evaluated the partial substitution of ordinary Portland cement with blended corn cob ash (CCA) and coconut shell ash (CSA) for sandcrete block production. Cement replacement levels of 0%, 5%, 10%, 15%, and 20% by weight were adopted. The density and compressive strength of the sandcrete blocks were measured at curing ages of 7, 14, and 28 days, whereas the water absorption was determined at 28 days. The results showed that CCA and CSA exhibited satisfactory characteristics as supplementary cementitious materials. The lower specific gravities of CCA and CSA (2.40 and 2.60, respectively) in comparison with that of cement (3.14) indicate the lightweight properties of the ashes, which contribute to reducing the density of cement-based materials. The consistency, initial setting time, and final setting time of the CCA-CSA-cement paste increased with increasing ash content. Block specimens containing 5%–10% CCA-CSA achieved acceptable physical and mechanical characteristics. The density, water absorption, and compressive strength values of the sandcrete blocks containing 0%–15% CCA-CSA satisfied the standards for construction of non-load-bearing walling units. The partial substitution of cement with blends of CCA and CSA will promote environmental sustainability and contribute to the development of a resource-efficient cementitious material that reduces reliance on conventional cement.