Performance enhancement of recycled aggregate concrete using active confinement and fibres

This study presents an integrated enhancement approach to improve the mechanical and durability properties of recycled aggregate concrete (RAC), which typically suffers from reduced strength and permeability. A novel combination of active lateral confinement systems (tri-tie, quad-tie, and steel clamps) and hybrid fibre reinforcement (steel and basalt fibres) was employed. Concrete mixes incorporating 50% recycled aggregates and varying fibre dosages were tested for compressive and tensile strength, ultrasonic pulse velocity (UPV), and water permeability. The highest compressive strength (35.0 MPa) and UPV (4.91 km/s) were achieved with 1.5% steel fibres and tri-tie confinement, while steel clamp systems yielded the lowest permeability (3.92 mm). The synergistic action of confinement-induced stress redistribution and fibre-bridging significantly enhanced RAC performance. This experimentally validated, scalable strategy demonstrates the potential for producing high-performance, durable RAC, facilitating its use in critical structural applications aligned with sustainable construction goals.