An experimental study of aggregate shape effect on dynamic compressive behaviours of cementitious mortar

Abstract

An experimental investigation is conducted to study the effect of aggregate shape on mortar dynamic failure behaviours. Split Hopkinson bar device is employed to compress cylindrical mortar samples containing irregular glass aggregates and rounded glass aggregates under high strain rates from 1000 s−1 to 2500 s−1. A new insight into the aggregate shape effect on the mortar cracking mechanisms is presented at the microscale using micro-CT. The cracking characteristics are found to be highly dependent on the aggregate shape, where more rounded aggregates in mortar are less likely to possess transgranular cracks after the initiation of intergranular cracks in the weak interfacial transition zone. These microscopic cracking mechanisms are validated by the cumulative distribution evolutions of particle size and morphological parameters (elongation and flatness), which are further manifested by the dynamic compressive strength. The results demonstrate that mortar with more regular aggregates exhibits higher dynamic compressive strength and strain rate sensitivity.