Influences of interlock-dense gradation designed by discrete element method on properties of cement-stabilized recycled brick-concrete aggregates

An interlock-dense (IND) gradation was simulated and designed through step-by-step blending aggregates with various particle size based on the discrete element method (DEM). The force characteristics of the recycled brick-concrete aggregates (RBCA) with IND gradation and other two gradations proposed by Chinese Specification were investigated through establishing a three-dimensional numerical model and a crushable numerical model. The influences of various gradations and cement contents on physical and mechanical properties of the cement-stabilized materials (CSM) prepared by using RBCA with various brick contents were investigated and discussed through laboratory tests. The results indicated that the brick and concrete recycled aggregates can jointly form a force chain to transmit load when the aggregates with IND gradation bear a small load, but when the brick aggregates were broken under load they mainly act as fillers between concrete aggregates to increase coordi-nation number and distribute load, increasing the stability of the new force chains. The testing results indicated that the maximum dry density and optimum water content of the CSM prepared by using RBCA with IND gradation are between those prepared by using other two gradations, but the unconfined compressive strength and the compressive resilience modulus at 90d are the highest. Under the same other conditions, it showed the lowest drying shrinkage when the brick content in RBCA was 15%. However, when the brick content was 30% and 45%, the drying shrinkage lied in between them.