The quality classification of recycled aggregate is based on the water absorption rate and the density of the adhered mortar. However, the quality of recycled aggregate is affected by the adhesion characteristics between the original aggregate and mortar (Interfacial Transition Zone: ITZ). It has been reported that carbonation of recycled aggregate improves mortar quality, but the effect on the above adhesion interface is not clearly evaluated. In this study, laser-induced vibration method is conducted on recycled aggregate before and after carbonation to evaluate the quality of the adhesion interface between the aggregate and mortar. A simple spring model, in which the adhesion strength of the interface is expressed as a spring constant, is applied to the quality evaluation of the recycled aggregate. As a result, it is found that there is a correlation with Vickers hardness, which can measure the strength of the interface.
