Transforming Waste into Strength: Sustainable Applications of Recycled Aggregates in Concrete Production a Comprehensive review

Abstract
The increasing generation of construction and demolition (C&D) waste has raised significant environmental and economic concerns worldwide, emphasizing the need for sustainable recycling practices in the construction industry. Recent research highlights the potential of recycled concrete aggregates (RCA) derived from C&D waste as a partial or complete
replacement for natural aggregates in concrete production. Studies reveal that RCA generally exhibit higher porosity and water absorption due to adhered mortar, influencing workability, density, and mechanical performance of concrete. Nonetheless, when properly processed and graded, RCA can achieve compressive strengths and durability levels comparable to
conventional mixes, particularly in non-structural and medium-strength applications. Investigations into durability performance indicate that recycled aggregate concrete (RAC) may experience increased carbonation depth, chloride ingress, and freeze–thaw sensitivity, though optimized mix designs, admixtures, and surface treatments can mitigate these effects. Beyond structural concrete, RCA has been successfully incorporated into melded bricks and blocks, offering viable pathways for large-scale utilization. Fine recycled aggregates (FRCA) also present opportunities but require careful mix proportioning to address strength and durability concerns.