Effect of carbonated recycled aggregates on the mechanical properties and bonding performance of polyurethane mortar as a repair material

Abstract Recycled aggregate (RA) made from construction waste has limited application due to its high porosity, numerous cracks, and other disadvantages such as reduced concrete strength when using aggregate). In this paper, carbonated recycled aggregate (CRA) was obtained by carbonating recycled aggregate, and natural aggregate (NA) in polyurethane mortar (PUM) was replaced at different ratios. The physical changes and pore structure of RA before and after carbonation, the mechanical properties (compressive and flexural strength) of PUM, and the three-point bending bond performance were systematically investigated. The compactness of PUM was detected by ultrasonic velocity (UPV) test. The change mechanism of PUM microstructure was revealed by scanning electron microscopy (SEM). The results show that when the replacement rate is 50%, the compressive and flexural strength of carbonated PUM increased by 7.32% and 15.83%, respectively, and bond strength increased by 14.19%, all of which are greater than the increase at a replacement rate of 25%. The mechanical properties of P with RA as aggregate decreased, but the generated calcium carbonate after carbonation treatment can fill the surface pores and enhance the pore structure of CRA, and the mechanical properties of three-point bending bond performance of the test pieces with the same replacement ratio were improved compared with those replaced by RA.