Shape Effect of Crushed Sand Filler on Rheology: A Preliminary Experimental and Numerical Study

Two types of filler from crushed sand were mixed with cement paste with constant superplasticizer dosage per mass of cement to investigate how their shape affects the rheology. The fillers were mylonitic quartz diorite and limestone produced using Vertical Shaft Impact (VSI) crusher and air classification, and had length/thickness (L/T) aspect ratios of 2.00 and 1.82, respectively. The particles were characterized with X-ray micro-computed tomography, coupled with spherical harmonic analysis to mathematically describe the full 3-D shape of the particles, while the rheological performance was quantified with the slump flow test (i.e. mini cone). The shape effect was isolated in the experiments by the use of non overlapping bimodal particle distributions of cement particles with a number average diameter of approximate to 0.01 mm and filler particles with a number average diameter of approximate to 0.1 mm. The two filler types were tested with a range of chi-values (volume of cement divided by total volume of solids). The flowability of the matrix increased with decreasing aspect ratios of the filler. However, the chi-value at which the maximum volume fraction threshold was obtained varied for the two filler types. Subsequently, a discrete element model was utilized to simulate the experimental data, thereby providing an initial step toward a numerical tool that can assist when proportioning self-compacting concrete with high volumes of crushed sand fines.