Non-destructive evaluation of residual strength and bond performance in recycled coarse aggregate concrete with deformed bars of varying diameters and strengths

Abstract

This study investigates the use of Recycled Coarse Aggregates (RCA) as a partial or full replacement for Natural Aggregates (NA) in structural concrete, addressing the rising Construction and Demolition (C&D) waste in India. Although environmentally beneficial, RCA use in structural applications is limited due to concerns over strength and durability. To assess its feasibility, bond strength between RCA concrete and steel reinforcement was tested using the RILEM pull-out method and simulated in ANSYS Workbench. Non-Destructive Testing (NDT), particularly Ultrasonic Pulse Velocity (UPV), was used to evaluate compressive strength, dynamic elastic modulus, and durability indicators. Results showed that M30 concrete with 25% RCA outperformed conventional concrete in strength. A 2.3% reduction in bond strength was observed with 16 mm bars, while 100% RCA with 20 mm bars showed a 1.25% improvement. In M50 concrete, up to 50% RCA retained adequate strength, with bond performance influenced by bar diameter. The dynamic elastic modulus was 48% higher than the static value. Acid exposure caused visible surface deterioration, indicating possible durability concerns. Overall, RCA can be effectively used in structural concrete with proper design and quality control. The study also emphasizes the relevance of NDT methods in assessing the performance of RCA concrete.