Study on the Influence of the Properties of Interfacial Transition Zones on the Performance of Recycled Aggregate Concrete

Applying recycled aggregate (RA) aligns with the development concept of green and environmental protection. Nevertheless, introducing RA has resulted in a complex interface structure, which will deteriorate the performance of recycled aggregate concrete(RAC). To investigate the influence of the properties of the interfacial transition zones(ITZs) on the performance of RAC, and the digital image correlation(DIC) technology was used to track the strain variation law of each interface during the failure process. The porosity and mechanical properties of the ITZs were quantitatively characterized by backscattered electron(BSE) imaging and microhardness testing. By controlling a single variable, the different ITZs of RAC were improved by targeted strengthening, including mortar and aggregate strengthening.The influence of the ITZs properties on the macroscopic properties and mesoscopic failure behavior of RAC was analyzed. The experimental results show that the mechanical properties of the ITZs were enhanced and the porosity was reduced. Strengthening treatment improved the strength of target interface, causing a change in the relative strength of the internal interface of concrete, and reducing the probability of failure of the strengthened interface. This is consistent with the results observed in SEM images, the more compact and stable the structure at the interface, the lower the probability of failure under load. A comprehensive evaluation of mortar strengthening and aggregate strengthening was carried out with the help of the linear weighted sum method, and the results showed that the mortar strengthening was more effective.