The recycle of the building and demolition waste could reduce project expenses and save natural resources as well as solve problem about environmental risks incurred during the disposal of building waste. In this study, waste C30 concrete is taken an experimental material. The mass loss, ultrasonic velocity, dynamic modulus of elasticity and cubic compressive strength of recycled coarse aggregate concrete whose coarse aggregate replacement percentage is 25%, 50%, 75%, and 100% are tested and compared with NAC when the cycles of freezing and thawing are 0, 25, 50, 75, 100, 125, 150, 175, and 200 times. The results show: (1) Generally, the loss of mass, ultrasonic velocity, dynamic modulus of elasticity and cubic compressive strength constantly increase with the growth of freezing and thawing cycles. (2) Compared with the recycled concrete of other replacement percentages, the RAC50 shows relatively close performance to NAC in mass loss, the change of dynamic modulus of elasticity and cubic compressive strength. (3) Performances of RAC25 specimens are better than the other RAC specimens for the ultrasonic wave velocity.

A quantitative study is performed to determine the performance degradation of Y-shaped reinforced concrete bridge piers owing to long-term freeze-thaw damage. The piers are discretized into spatial solid elements using the ANSYS Workbench finite element analysis software, and a spatial model is established. The analysis addresses the mechanical performance of the piers under monotonic loading, and their seismic performance under low-cycle repeated loading. The influence of the number of freeze-thaw cycles, axial compression ratio, and loading direction on the pier bearing capacity index and seismic performance index is investigated. The results show that freeze-thaw damage has an adverse effect on the ultimate bearing capacity and seismic performance of Y-shaped bridge piers in the transverse and longitudinal directions. The pier peak load and displacement ductility coefficient decrease with increasing number of freeze-thaw cycles. The axial compression ratio is an important factor that affects the pier ultimate bearing capacity and seismic performance. Upon increasing the axial compression ratio, the pier peak load increases and the displacement ductility coefficient decreases, the effects of which are more significant in the longitudinal direction.

Incorporation of air-entraining agent has improved recycled concrete freeze-proof durability. However, it is very lacking to study the role of the entraining agent. In this paper, the influence of an air-entraining agent on freeze-proof durability for the ordinary C30 recycled coarse aggregate (RCA) concrete and air-entrained C30 RCA concrete was investigated with the laboratory comparative tests. The mass loss, the dynamic modulus of elasticity, ultrasonic wave velocity and cubic compressive strength were measured during freeze-thaw cycles. The test result showed the concrete’s performance was similar to the ordinary concrete and was better than that of other recycled concretes when the content of RCA was 50% and 0.03% of air-entraining agent was added for C30 RCA concrete. Meanwhile, the addition of air-entraining agent has an improved effect on the performance of recycled concrete, but the effect was limited.