Performance and Sustainability of Concrete Incorporating Wood Ash and Crushed Clay Blocks: An Experimental Study

This study evaluates the feasibility of utilizing wood ash (WA), derived from grilled-fish barbecue waste, as a supplementary cementitious material, in combination with crushed clay blocks (CCB) as partial or full replacements for natural coarse aggregate, to improve the sustainability of concrete. A total of twelve concrete mixtures were produced using WA replacement levels of 0%, 10%, 20%, and 30% and CCB replacement levels of 0%, 50%, and 100%. The concrete specimens were evaluated in terms of workability, compressive strength, splitting tensile strength, flexural strength, density, water absorption, ultrasonic pulse velocity (UPV), thermal conductivity, and microstructural characteristics using scanning electron microscopy (SEM). The results show that replacing cement with 10% WA achieved the highest mechanical performance at 56 days, with compressive, splitting tensile, and flexural strengths of 50.58 MPa, 5.54 MPa, and 6.07 MPa, respectively. These results represent an improvement of 11% in concrete properties compared with the control mixture. However, the use of 20% of WA enhanced microstructural densification through pozzolanic reactions, whereas higher replacement levels resulted in increased porosity, the presence of unreacted particles, and reductions in strength and UPV values. In contrast, increasing the WA and CCB contents reduced density and workability while significantly increasing water absorption. Among the investigated mixtures, the combination of 10% WA and 50% CCB provided the most favorable balance between mechanical performance, thermal efficiency, and sustainability. Further studies are recommended to evaluate the long-term durability and economic feasibility of the proposed replacement levels for sustainable concrete production.