Influence of construction and demolition waste grades on crushing efficiency, utility factor, recycled aggregate properties and their environmental indicators

This study investigates the influence of CDW grades on crushing efficiency, the utility factor and recycled aggregate characteristics, focusing on concrete waste (C1, C2, C3) and brick waste (B1, B2, B3). An inverse relationship exists between CDW grades and crushing efficiency, with 6.7%–12.1% decrement for every 5 MPa strength increment. The utility factor improved with increasing CDW strength, showing 1.62%–1.80% increment per 5 MPa strength increment. Physical characteristics showed concrete waste grade C1 is suitable for structural applications, resembling conventional fine aggregate (M-sand). Water absorption increases 1.5–2.0 times with increasing CDW grade, while specific gravity decreases. Lower grade CDW showed higher aggregate impact value and aggregate crushing value, indicating a lower resistance to loads. Embodied Energy and Embodied Carbon increase with higher-grade of CDW, with concrete waste showing 19.71%–46.03% increase in EE and 19.79%–46.27% increase in EC per two-fold increase in strength. Brick waste showed over 50% increment in EE and EC for higher-grades. Higher-grade CDW requires more energy but demonstrates improved utility factors (>90% for C3 and B3) compared to lower grades (81.32% for C1, 80.67% for B1). The outcome of the current study emphasizes decision making strategy on crushing of CDW based on the strength grade, crushing efficiency and utility factor. This approach promotes scientific and application specific crushing of CDW, leading to a sustainable construction practice by minimizing environmental impacts.