干湿或冻融循环条件下建筑固废再生填料颗粒强度特性研究OA

To promote the application of recycled filler particles from construction demolition waste in railway subgrade engineering subjected to harsh service environments,this study focuses on the initial deterioration effects induced by two typical environmental actions:freeze-thaw cycles and wetting-drying cycles.Systematic single-particle crushing tests and nanoindentation tests were conducted on recycled brick and recycled concrete aggregate particles.A comprehensive analysis was performed on the macro-scale fracture patterns,Weibull characteristic strength,crushing energy per unit volume,and the evolution of mechanical properties of different microscopic phases(including aggregate,cement paste,and brick matrix)under varying environmental degradation conditions(0,3,5,7,and 10 freeze-thaw or wet-drying cycles).The results indicate that the fracture modes of single recycled filler aggregate particles can be classified into three types:brittle fracture(single peak),mild fragmentation(double peak),and severe fragmentation(multiple peaks).Environmental degradation significantly increases the proportion of double-peak and multiple-peak fracture modes.The characteristic strength of recycled concrete particles is significantly higher than that of recycled brick particles,and the latter exhibits greater sensitivity to environmental deterioration,especially wetting-drying cycles.As the number of freeze-thaw or wet-drying cycles increases,the mean crushing energy per unit volume of particles generally decreases.After degradation,the distribution of crushing energy tends to concentrate,and the proportion of low-energy fractures increases.At the microscopic scale,the indentation hardness and modulus of the aggregate phase in recycled concrete particles are the highest,followed by the brick matrix,with cement paste showing the lowest values.Environmental degradation affects the mechanical properties of the constituent phases in the following descending order:brick matrix,cement paste,and aggregate.The findings of this study provide theoretical insights and technical support for the gradation design and durability optimization of recycled filler from construction demolition waste in railway subgrade engineering.