Performance-based classification of fibre-reinforced recycled aggregate concrete: a state-of-the-art review

The depletion of natural aggregates (NA) and the rapid generation of construction and demolition waste (CDW) have driven the construction industry toward sustainable alternatives. Recycled concrete aggregate (RCA) offers a promising substitute for NA, promoting resource conservation and waste reduction. However, RCA’s adhered mortar leads to higher porosity, lower specific gravity, and reduced mechanical and durability performance, limiting its structural use. Fibre reinforcement has emerged as an effective strategy to overcome these drawbacks by bridging cracks, improving ductility, and reducing shrinkage. Steel fibres enhance flexural strength and toughness; carbon fibres improve tensile strength, durability, and self-sensing capability; natural fibres provide low-cost, renewable reinforcement with improved crack control but require treatment for durability; and hybrid fibres yield synergistic gains in strength, toughness, and ductility. This review examines RCA classification, performance limitations at full replacement, and the role of various fibres in enhancing recycled aggregate concrete (RAC). Experimental evidence confirms significant improvements in mechanical and durability properties, with hybrid systems showing the most consistent benefits. Future research should focus on nano-modified fibres, hybrid optimization, and standardized design frameworks to establish fibre-reinforced RAC as a sustainable, high-performance material for modern infrastructure.