Fresh and Hardened Properties of Low-Clinker Cementitious Systems with Low-Co2 Footprint Produced with Carbonated Fine Recycled Aggregates

Concrete production is a major contributor to greenhouse gas emissions, mainly from the calcination of limestone to manufacture clinker. To address this issue, there is growing interest in developing more sustainable and eco-friendly alternatives to traditional concrete. One approach is developing composite cement to replace some clinker with supplementary cementitious materials (SCMs). Another solution is the carbonation of recycled concrete aggregates (RCA), a process that sequesters CO2 and improves the resulting concrete's mechanical properties. Few studies focus on the carbonation of fine recycled aggregates (fRCA), therefore, this study investigates the combined use of low-clinker cement and fine recycled concrete aggregate carbonation. Specifically, this study examined how different levels of substitution of carbonated fRCA affect the fresh properties (flow test) and hardened properties (compressive strength, flexural strength) of low-clinker cementitious systems. For this purpose, mortar mixtures were produced, substituting 0%, 50%, and 100% of the river sand by treated fRCA after subjecting to one-hour moist carbonation. In all mixtures, water/binder, sand/binder, and slump flow values were kept constant at 0.5, 3, and 175 ± 10 mm, respectively. High-range water-reducing admixture and adjusted water were added to provide the targeted slump-flow range of each mixture. The results showed that incorporating treated fRCA into low-clinker cementitious systems can improve their mechanical properties. Considering the industry's efforts to reduce CO2 emissions, this research could contribute to developing more sustainable building materials.