Pore size distribution and ITZ performance of mortars prepared with different bio-deposition approaches for the treatment of recycled concrete aggregate

This study aims to clarify the role of bio-deposition in improving the properties of recycled concrete aggregate (RCA) to enhance its reusability. Two bio-deposition treatments were investigated (immersion and spraying). The physical properties, pore structure, and micro-morphology of the RCA were investigated both before and after treatment, and the compressive and flexural strength of mortars prepared with treated and untreated RCA were also analysed. In addition, the micro-mechanical properties of the hydration products of bio-calcium carbonate were determined. The results showed that the water absorption, porosity, and crushing values of treated RCAs were lower than those of untreated RCAs. The compressive and flexural strength of mortars made with untreated RCAs were lower than those of mortars with treated RCAs. The results show that bio-calcium carbonate and its hydration products have a positive effect on the interfacial transition zone of the mortars, thereby reducing crack widths and improving the micro-mechanical properties.