The influence of particle shape and particle size on the work-ability properties of SCC mortars

Experimental investigations using natural and crushed sands have demonstrated that the packing density of the sands is the decisive factor influencing the workability properties of mortars for self compacting concrete (SCC). The latter have been characterized for a specified mortar formulation on the basis of the quantity of plasticizer necessary for a selected slump flow and on the basis of funnel flow time. Packing density, for its part, is dependent on particle-size distribution (with only the width of distribution playing an influencing role) and on the particle shape of the aggregate. It rises up to a maximum both as distributions become broader and as particle geometries improve. The results show that identical packing densities can be achieved both with broad particle-size distributions and poor particle shapes (crushed sands) and with tight distributions and good particle shapes (natural sands). Given knowledge of the particle-size distribution and particle-shape parameters of a sand, corresponding to the selected test conditions, the correlations obtained could make it possible to provide an initial statement concerning the possible utilization of the sand as a component in an SCC.