Improved performance of recycled aggregate concrete using a combined treatment approach

The use of recycled aggregates (RA) in structural concrete is limited by adhered mortar, high porosity, and weak interfacial transition zones, which adversely affect durability and mechanical performance. A combined treatment approach for RA integrates mild acetic acid pre-soaking, controlled mechanical grinding (0–600 Los Angeles abrasion revolutions), and short-duration pressurised carbonation to enhance aggregate quality and concrete performance. Treated aggregates were incorporated into M40-grade concrete at 0%–100% replacement of natural aggregates. Fresh and hardened properties were evaluated through slump, compressive strength at 28 and 90 days, ultrasonic pulse velocity, surface resistivity, abrasion resistance, and sulfate attack tests. Results show systematic improvements in workability, mechanical properties, and durability indicators with increasing treatment intensity. The optimal condition was identified at 500 abrasion revolutions (RVs), where effective mortar removal and carbonation-induced CaCO₃ precipitation refined the pore structure and densified the interfacial transition zone. At 60% aggregate replacement, the optimised concrete achieved a 28-day compressive strength of 40.90 MPa, satisfying M40 requirements, while showing substantial gains in permeability resistance, abrasion resistance, and sulfate durability compared with untreated RA concrete. The findings demonstrate that a combined treatment approach can significantly enhance the durability and performance of RA concrete, supporting its use in structural applications.