Reutilization of Recycled CDW Sand in Mortars, Paving Blocks, and Structural Concrete

Abstract

Featured Application: This study examines the technical viability of using industrially processed construction and demolition waste (CDW) with a limestone–ceramic composition, washed to remove sulphates, as a fine aggregate (sand) in mortars, paving blocks, and structural concrete. Reusing construction and demolition waste (CDW) as recycled aggregate reduces environmental impact and enhances resource efficiency. While previous research has mainly focused on the use of recycled aggregates (RAs) in concrete, this study evaluates the use of CDW-derived sand in mortars, paving blocks, and structural concrete. Natural and CDW aggregates were characterized, and samples were prepared with two types of Portland cement, replacing up to 100% of the natural limestone sand. Tests were conducted to assess workability, density, strength, and durability. CDW aggregates, primarily composed of limestone and ceramics, reduced sample density as their content increased. Workability improved in the mortars and concrete with higher CDW contents, peaking at 20% CDW in paving blocks. Although the permeability of concrete increased with CDW content, the developed recycled aggregate concrete (RAC) met structural code requirements for all the exposure classes. Despite the decline in strength with higher CDW content, the paving blocks maintained a relative tensile splitting strength above 80%, and the relative compressive strength of the mortars cured for 28 days exceeded 70%. The RAC compressive strength remained within the required range for reinforced concrete (>25–30 MPa). These results validate the feasibility of using CDW-derived sand in various sustainable construction applications with minimal strength loss. Furthermore, they contribute to the development of standardized guidelines for RAs in non-structural applications, fostering broader industry adoption and environmental benefits. © 2025 by the authors.