Energy Consumption and Carbon Emissions of Compressed Earth Blocks Stabilized with Recycled Cement

Driven by the pursuit of more sustainable materials, earth construction has seen renewed interest in recent years. However, chemical stabilization is often required to ensure adequate water resistance. While recycled cement from concrete waste (RCC) has recently emerged as a more sustainable alternative to ordinary Portland cement (OPC) for soil stabilization, its environmental impact remains unassessed. A hybrid model, built on collected data and direct simulations, was implemented to estimate energy and carbon emissions of compressed earth blocks (CEBs) stabilized with RCC as a partial or total replacement of OPC. Four operational scenarios were assessed in a cradle-to-gate approach, evaluating the environmental impact per CEB unit, and normalizing it to the CEB compressive strength. OPC CEBs showed up to 9 times higher energy consumption (2.46 vs. 0.24 MJ/CEB) and about 35 times higher carbon emissions (0.438 vs. 0.012 kgCO₂/CEB) than UCEBs. However, replacing OPC with RCC reduced energy consumption by up to 8% and carbon emissions by up to 64%. Although RCC CEBs showed lower mechanical strength, resulting in higher energy consumption when normalized to compressive strength, carbon emissions remained up to 48% lower compared to OPC CEBs. RCC emerged as a more sustainable alternative to OPC for earth stabilization, while also improving the mechanical strength and durability of UCEBs.