Discrete element analysis of the effect of aggregate morphology on the flowability of self-compacting concrete

As the filling layer material of CRTS III slab ballastless track structure, self-compacting concrete (SCC) requires good fluidity. In this paper, the 3D laser scanning technology and digital image processing technology were used to characterize the aggregate morphology quantitatively, and an aggregate classification method considering the angularity of mesoscale was proposed. Meanwhile, aggregate particles with natural morphology were generated by Clump method, and the slump-flow test of SCC was simulated in 3D by the discrete element method (DEM) based on the adhesive rolling resistance linear model. On this basis, the effect of aggregate morphology on the flowability of self-compacting concrete was quantitatively studied, and the explanation was given from the perspectives of aggregate voidage and aggregate behavior. The results show that aggregate's macro-shape has twice the effect on self-compacting concrete flowability as aggregate's meso-angularity. For the sake of obtaining better flowability of self-compacting concrete, the priority order of aggregate is smooth spherical aggregate, multi-angular spherical aggregate, smooth elongated-flaky aggregate and multi-angular elongated-flaky aggregate. In addition, the flowability of self-compacting concrete is inversely proportional to the content of multi-angular elongated-flaky aggregate. The content of multi-angular elongated-flaky aggregate in self-compacting concrete for use as track filling layer should be kept below 10 %.