Parametric Effects of Processed and Treated Aggregates on the Strength and Durability of Green Concrete via Response Surface Methodology

This study investigates the effects of incorporating Processed Recycled Aggregates (PRA) and Treated Recycled Aggregates (TRA) on the workability, mechanical properties, and durability of concrete. Recycled aggregates are increasingly considered for sustainable construction, but their impact on concrete performance requires thorough evaluation. The study explores mixtures with PRA replacing natural aggregates at varying levels (0%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, and 100%) and the inclusion of TRA. The results reveal significant reductions in workability and compressive strength as PRA content increases. The slump decreased from 135 mm to 40 mm, and the compressive strength dropped notably from 85.43 MPa to 35.49 MPa. Durability concerns are highlighted by the increase in water absorption (from 0.45% to 1.89%) and Rapid Chloride Penetration Test (RCPT) values (from 1821 to 4618 coulombs), indicating higher porosity and permeability with increasing PRA. Additionally, the modulus of elasticity decreased from 43.44 GPa to 28.01 GPa, while the Ultrasonic Pulse Velocity (UPV) decreased from 4563 m/s to 3853 m/s, suggesting a reduction in concrete stiffness and quality. The 3D surface plots illustrate these trends, providing a visual representation of the decline in performance metrics with higher PRA content. The findings underscore the trade-offs between sustainability and structural performance, emphasizing the need for optimizing recycled aggregate content to balance environmental benefits with mechanical and durability requirements in concrete applications.