English：

With the continuous development of infrastructure, the amount of abandoned building concreteis increasing, and the processing cost is also constantly rising. In order to reduce construction costs andimprove the recycling rate of construction waste in engineering, research is being conducted on theapplication of low,cost recycled aggregate concrete in the cushion layer. The influence of recycled fineaggregate substitution rate and pretreatment form on the flowability and mechanical properties of concretewas studied through single factor experiments, and the optimal substitution rate of recycled fine aggregatethat meets application requirements was obtained. The results indicate that the addition of recycled fineaggregate will reduce the flowability of concrete; The replacement rate of recycled fine aggregate within40% can improve the compressive strength of concrete within 7 days; The compressive strength andsplitting tensile strength at 28 days gradually decrease with the increase of recycled fine aggregatecontent; The optimal substitution rate of recycled fine aggregate is 40%, and the optimal pretreatmentform is pre wetted recycled fine aggregate. The application of recycled fine aggregate concrete in thecushion layer has advantages such as green environmental protection and cost reduction.