Effect of salty freeze-thaw cycles on durability of thermal insulation concrete with recycled aggregates

An experimental study on the durability of thermal insulation concrete with recycled aggregates (RATIC) subjected to the combined action of chloride salt erosion with 3.5% NaCl solution and freeze-thaw cycles (referred to as salty F-T cycles) has been carried out. In this study, the volume of the natural coarse aggregates has been replaced by recycled coarse aggregates (RCA) at replacement rates of 0%, 30%, 50%, 70%, and 100%. The results show that thermal insulation aggregate glazed hollow beads (GHBs) had a positive effect on the durability of concrete and RCA had an enormous negative influence on the durability of RATIC exposed to the salty F-T cycles. After 100 salty F-T cycles, the relative dynamic modulus of the elasticity of samples with RCA was below 60% compared to at the start of the F-T cycles. RCA has a significant effect on the chloride permeability of RATIC compared to natural aggregates. This phenomenon was caused by the special multi-interfaces structure of RATIC that are the result of the old interfacial translation zones (ITZs). These aggravate frost damage and negatively affect the durability of concrete in the salty F-T cycles environment.