Proposal of Non-destructive Quality Assessment for Recycled Aggregate with Evaluation of Vibrational Behavior at ITZ

The mechanical properties of the interfacial transition zone (ITZ) in recycled coarse aggregate (RA) significantly affect the quality of recycled coarse aggregate concrete (RAC). However, there is currently no non-destructive method established to evaluate the mechanical properties of ITZ directly. This study proposes a novel quality evaluation method for RAs using a laser-induced vibration test and a simplified rigid body spring model (RBSM). First, compression tests and steel ball impact tests were conducted on specimens that simulated the simplified RBSM to verify the simplified RBSM. Then, the elastic modulus of the ITZ was measured by nano-indentation tests to estimate the eigenfrequency of RA. After that, the elastic property of ITZ was estimated using the simplified RBSM and the eigenfrequency of RA. As a result, a correlation was observed between the spring constants of ITZ and the compressive strength of RCA. This suggests the adaptability of the proposed method to RA quality evaluation using the laser-induced vibration test and the simplified RBSM.