Sustainable brick production using waste foundry sand and cast-iron slag: Reductions in embodied energy, CO₂ emissions, and cost

Waste foundry sand (WFS) and cast-iron slag (CIS) are industrial wastes that are generated in large quantities during the production of cast iron worldwide, and for which various solutions are sought for their disposal. In this study, these two wastes were used together for the first time in the production of fired bricks to provide clay substitution, as well as to reduce embodied energy, CO 2 emissions, and costs. Modified bricks were produced with varying proportions of WFS and CIS (both up to 20 %) and fired at 850 °C, 950 °C, and 1050 °C. The physical, mechanical, and microstructural properties of the bricks were evaluated, along with an assessment of their embodied energy and CO 2 emissions. Results showed that bricks fired at 1050 °C met the standards for high-strength load-bearing applications, with water absorption values within acceptable limits. Using 20 % CIS and 10 % WFS resulted in lower water absorption compared to reference bricks, while dual-component mixtures (5 % CIS + 10 % WFS) exhibited superior mechanical performance. Microstructural analysis confirmed that the additives enhanced the densification of the brick matrix. Notably, incorporating WFS and CIS reduced embodied energy by 15.22 % and CO 2 emissions by 15.87 %, with bricks containing 20 % WFS being 2.11–2.23 % cheaper to produce. Energy costs were identified as the primary expense, with the energy required to reach firing temperature having a greater impact than the firing process itself. The study concludes that WFS and CIS are effective additives for sustainable brick production, offering significant environmental and economic benefits. • Quartz-rich waste foundry sand and cast-iron slag was used in fired brick production. • Bricks with waste added after firing showed physical and mechanical properties close to the reference bricks. • Bricks with 20 % waste foundry sand reduced CO 2 emissions by about 16 %. • Use of foundry waste reduced brick production costs by approximately 2.2 %.