Gradation optimization of continuous-graded crushed sand based on mortar performance

Abstract

Compared to river sand, crushed sand is characterized with higher irregularity of fine aggregate with size 0.075–4.75 mm and rock powder content with size <0.075 mm, which makes it is difficult to meet application requirements only by its sieving gradation. In the case of meeting the limitations of continuous gradation sand, the packing void fractions n and fineness modulus M of the continuous-graded crushed sand were proposed together to characterize fine aggregate gradation, which should vary with 41.8–45.0 % and 2.9–3.2 respectively to guarantee the prepared mortar with better strength and workability, while the rational rock powder content was 6–9 %. It was also found that there was a significant correlation between the yield shear stress τ0 of the mortar prepared with continuous-graded crushed sand and its slump flow SF, while the plastic viscosity η has a significant correlation with the its segregation resistance SR. Finally, the predicting formula of slump flow SF was obtained, which could be used to optimize the sand gradation further, and the plastic viscosity η should be not less than 17 Pa∙s to ensure good anti-segregation.