Assessing mortar durability with recycled concrete powder: toward circular use of construction materials

Abstract The global construction industry is increasingly prioritizing sustainability and circular economy principles to reduce environmental impacts and improve material efficiency. One promising strategy involves incorporating recycled concrete powder (RCP), a byproduct of construction waste processing, as a supplementary cementitious material in mortar. This approach reduces cement consumption and CO₂ emissions while diverting demolition waste from landfills. However, the performance of RCP in cementitious systems depends strongly on particle fineness, which governs reactivity, packing density, and microstructural development. This study investigates the durability of mortars containing RCP with two particle sizes: RCP1 (passing sieve No. 200) and RCP2 (passing sieve No. 360), used at 0%, 15%, 20%, and 25% cement replacement levels. Durability parameters such as porosity, water absorption, sorptivity, cohesion, and abrasion resistance were evaluated at 28 and 90 days. A three-way ANOVA showed that RCP fineness and curing age significantly affected porosity, water absorption, and sorptivity ( p < 0.05), while replacement ratio primarily governed abrasion loss. Significant fineness-replacement interactions indicate stronger benefits of finer RCP at higher substitution levels. Regression analysis confirmed RCP fineness as the main negative predictor of moisture-related durability parameters, whereas replacement ratio was the dominant positive predictor of abrasion loss due to cement dilution. Scanning electron microscopy (SEM) analysis further verified the formation of a denser, more compact microstructure in RCP2 mortars. Although compressive strength decreased with increasing RCP content, RCP2 exhibited enhanced strength development over time due to secondary pozzolanic reactions and improved particle packing. Overall, the results demonstrate that optimizing RCP fineness is essential to enhance the long-term performance of sustainable mortars, balancing strength, durability, and environmental benefits.