Pre-treatment of reclaimed concrete slurry waste for substituting cementitious materials: Effect of treatment approach and substitution content

Abstract

Reclaimed concrete slurry waste (RCSW) is a corrosive and harmful substance that cannot be directly utilised in the manufacturing of recycled concrete and requires appropriate treatment. In this study, we investigated the effectiveness and environmental impact of different treatment approaches, namely sieving, shearing, and ball milling, on RCSW and the feasibility of substituting Portland cement with substitution ratios of 15%, 30%, and 45%. The hydration properties, microstructural characteristics, and mechanical strength of cement pastes substituted with treated RCSW were investigated. The results indicated that among the three methods, shearing and ball milling offered RCSW with a smaller particle size and higher roundness. The cement paste containing 15% treated RCSW exhibited higher strength. The strength was significantly reduced when the substitution ratio of RCSW was higher than 30%. This is attributed to the improved hydration process owing to the treatments offering a denser cement paste structure. According to economic and environmental calculations, substitution with RCSW reduces carbon dioxide emission, with ball milling resulting in the lowest carbon footprint.