Valorization of steel slag in clay: Thermophysical study and energy simulation in Oujda (Morocco)

The valorization of industrial by-products is key to sustainable construction. This study investigates the use of Steel Slag Aggregate (SSA), a waste product from the Moroccan steel industry, as a partial replacement for clay in unfired bricks. Clay-soil from the Alouana region was mixed with SSA at proportions of 0, 10, 20, and 30 wt%. A detailed thermophysical characterization of the composites was conducted, and the obtained data were integrated into a dynamic energy simulation of a standard building in Oujda, Morocco, using TRNSYS. The results demonstrate that incorporating 30% SSA leads to a significant improvement in thermal performance: thermal conductivity decreases from 1.127 W/m·K to 0.88 W/m·K (a 21.9% reduction), thermal diffusivity drops by 34.4%, and specific heat capacity increases by 7.47%. The density also increased by 10.13%, suggesting enhanced compactness. The energy simulation for a semi-arid climate revealed that using clay bricks with 30% SSA can reduce the annual cooling energy demand by 13.62%, the heating demand by 8.29%, leading to a total annual energy saving of 12.80%. This research conclusively demonstrates that SSA is a highly effective additive for producing eco-friendly clay bricks with superior insulating properties, contributing to energy efficiency and waste recycling within a circular economy framework.