Speaker
Description
The construction sector is under increasing pressure to reduce greenhouse gas emissions, decrease its reliance on virgin raw materials, and implement circular economy principles. The valorization of recycled concrete fines (RCF) as a supplementary cementitious material offers a promising route for reducing clinker consumption and natural raw materials, lowering the carbon footprint of cement-based products, and improving resource efficiency in the construction industry. This study investigates the mechanical activation of RCF and its utilization as a partial replacement of Portland cement (PC) in cement mortars. RCF derived from waste concrete was mechanically activated using different milling protocols employing both a conventional ball mill and a high-energy planetary mill. Various material-to-ball ratios, milling speeds, and activation times were evaluated to identify the most effective activation pathway. The optimal activation conditions were achieved using a ball mill with a material-to-ball ratio of 10.4, milling speed of 70 rpm, and activation time of 20 min. Structural and geometrical activity were evaluated through chemical and mineralogical characterization, particle size distribution, and surface area analysis, while the reactivity of the activated material was assessed using the activity index. The mechanically activated RCF was incorporated into cement mortars as a replacement for PC at levels from 5 to 15 wt.%. The fresh and hardened properties of the mortars were evaluated, and the microstructure of the hardened mortars was also examined. All mortars containing activated RCF exhibited longer setting times and lower mechanical properties in comparison to the reference mortars; however, all mixtures satisfied the performance requirements for mortar applications.