颗粒破碎和界面损伤对水稳再生骨料透水基层材料强度的控制机理

Controlling mechanism of particle crushing and interfacial damage on the serength of cement-stabilized recycled aggregate permeable base material

随着我国“双碳”战略和“海绵城市”建设的持续推进,建筑固废再生骨料逐渐用于制作透水型水稳基层材料(CRAPBM)。为揭示再生骨料颗粒破碎和界面过渡区(ITZ)损伤对CRAPBM整体强度控制的微细观机理,首先分别对单个骨料颗粒和不同再生骨料组合类型的CRAPBM开展室内单颗粒破碎和单轴压缩试验,进而构建CRAPBM的精细化离散元模型(DEM)并由室内试验结果标定其细观强度参数,最后针对不同类型CRAPBM试样同时进行室内单轴压缩试验和相应的DEM模拟。研究结果表明:再生骨料的单颗粒强度和模量具有显著的尺寸效应,且天然碎石、再生砂浆、再生红砖的强度随粒径增大而降低;CRAPBM的骨架效应和空隙分布所导致的应力横向分化是加速ITZ损伤的主要原因,ITZ强度对CRAPBM整体强度具有显著的控制作用,而再生骨料的颗粒破碎会削弱ITZ的控制作用;4.75~9.50 mm粒径范围内的颗粒破碎最显著,级配优化时应尽量采用天然碎石替代该粒径区间的再生骨料以提高其整体强度。

With the continued efforts towards the "carbon peak and neutrality" strategy and "sponge city" initiative in our country,the construction and demolition wastes(CDWs) are increasingly recycled in massive quantities to produce cement-treated recycled aggregate permeable base materials(CRAPBM).The micromechanical mechanism of particle crushing and interface transition zone(ITZ) damage controlling macroscopic strength behavior of CRAPBM was revealed.The laboratory single particle crushing tests and uniaxial compression tests were first conducted on recycled CDW aggregate particles and CRAPBM specimens blended from virgin and recycled aggregates at different proportions,respectively.Then,the two-dimensional(2D) refined discrete element method(DEM) models were constructed for laboratory CRAPBM specimens with essential model parameters deliberately calibrated from related laboratory test results.Finally,a series of DEM simulations of laboratory uniaxial compression tests were performed for different types of CRAPBM.The results show that the singleparticle strength and modulus of aggregates exhibite significant size effect and follow the descending order of natural aggregates,recycled cement mortar and recycled red bricks.The lateral stress transmission caused by the aggregate skeleton effect and void distribution of CRAPBM is mainly attributed to accelerated ITZ damage,while the ITZ strength demonstrates a significant controlling effect on the overall strength of CRAPBM.The controlling effect of ITZ on the overall strength of CRAPBM is weakened by the particle crushing of recycled aggregates.The most significant particle crushing is observed for the size range of 4.75-9.50 mm,and the optimal approach for grading optimization is to replace recycled aggregate with natural gravel in the 4.75-9.50 mm particle size range to improve overall strength.