Valorisation of construction and demolition waste through recycling of fine aggregates towards reduced carbon dioxide footprint

A novel approach was adopted in this study – the use of real-world construction and demolition waste (CDW) as a source of recycled fine aggregate (RFA) for mortar production. Unlike in many previous studies, where laboratory waste was generated by casting and subsequently crushing concrete cubes, this research was based on heterogeneous, field-collected CDW, thereby reflecting the actual challenges of variability and contamination encountered in practice. The aim of this work was to optimise the percentage replacement of natural fine aggregate with RFA derived from real-world CDW rather than the more uniform laboratory-scale waste. Mortar mixes were prepared with 0–100% RFA replacement and their properties, including flow, bulk density, compressive strength, drying shrinkage, porosity, water absorption, sorptivity and resistance to acid and sulfate attack, were evaluated. The results showed that an increase in RFA content reduced workability, density and strength, and increased porosity, absorption and mass loss. However, for up to 50% replacement, the negative impact on strength and durability was minimal, while the cost was reduced by 12.8% and the carbon dioxide footprint was reduced by 10.55 kg_CO2/m³. The findings of this work establish a novel and sustainable framework for optimising RFA use in mortar, based on real-world CDW streams.