CO2 curing of mortar with natural and recycled concrete aggregate: An environmental and economic assessment

Previous studies have primarily focused on quantifying the impact of CO2 curing in terms of net CO2 emissions, overlooking its broader effect on the overall environmental performance of cementitious materials. This study aims to comprehensively assess the effect of CO2 curing on the performance and sustainability of mortars incorporating conventional and/or recycled materials (Recycled Concrete Aggregate (RCA) and Slag Cement (SC)). Four types of mixtures were analyzed, with two binder compositions (100% Ordinary Portland Cement (OPC) and 70% OPC + 30% SC) and two types of aggregates (Natural Aggregate (NA) and RCA). Each mixture had two groups of samples: one cured under normal conditions (reference group) and the other cured for 12 h in a CO2 curing chamber before starting normal curing. Strength, environmental impact, and cost were studied for all mixtures. Results showed that CO2 curing improved all single impact categories in environmental perfor-mance to varying extents. CO2 curing also enhanced the overall life cycle assessment results and reduced cost for all studied mortars. CO2 curing of cement mortars may, therefore, create a cheaper and more sustainable ma-terial. Using a Multi-Criteria Evaluation, it was demonstrated that CO2 curing increased the overall performance of all mixtures compared to conventional curing. Mortars containing recycled materials (e.g., RCA and/or SC) experienced significant improvements in terms of environmental performance despite their lower compressive strength. This suggests that CO2 curing may become a potential technology to enhance the sustainability of cement-based composites with recycled materials, contributing to a more environmentally friendly construction industry.