Potential evaluation of waste recycled aggregate concrete for structural concrete aggregate from freeze-thaw environment

•The feasibility of recycling waste RAC in freeze–thaw environment is evaluated.•Freeze-thaw damage of RAC adversely affect the properties of second-generation CRA.•Freeze-thaw damage threshold of waste RAC as CRA for structural concrete is 0.36.•RAC with freeze–thaw failure cannot reuse as CRA for structure concrete.•Adhesive mortar and ITZ are the main carriers of freeze–thaw damage transfer. The reuse of waste recycled aggregate concrete (RAC) from freeze-thaw (FT) environment as coarse recycle aggregate (CRA) for structural concrete can effectively improve the application of second-generation CRA. This paper evaluated the reuse potential of waste RAC suffered different FT cycles as CRA for structural concrete by FT damage. C40 RAC specimens with 100% replacement rate were produced and the FT damage through a coupled action of FT cycles and 35% bending load was assessed. The RAC were crushed into second-generation CRA after every 100 FT cycles until FT failure. Results showed that the evolution process of FT damage on physical properties of CRA can be divided into four stages: reinforcement stage, transition stage, weakening stage and failure stage. In the evolution process, the apparent density of second-generation CRA decreased with FT cycles, while the crushing value, water absorption and soundness (mass loss) increased. The particle size of second-generation CRA gradually decreased with the accumulation of FT damage, and the screening curve of the CRA after 400 FT cycles cannot meet the requirements of continuous particle size. Relative dynamic modulus of elasticity (RDME) was more sensitive than mass loss rate in assessing the frost resistance durability of RAC. The FT damage threshold of RAC based on the properties requirements of type II and type III CRA was 0.085 and 0.359, respectively, indicating that the FT damage threshold of waste RAC crushing as CRA for structural concrete was 0.36, and the corresponding RDME was 64% rather than 60%. The microscopic analysis showed that the weakening of adhesive mortar and ITZ was the fundamental reason for the decrease of physical properties of the second-generation CRA. The CRA obtained from the RAC with FT failure cannot be reuse as aggregates for structure concrete.