Study of the Failure Mechanism of Mortar Rubble Using Digital Image Correlation, Acoustic Emission and Scanning Electron Microscopy

Abstract

This paper describes an extensive experimental study of the compressive failure of different types of aggregates and the influence of aggregate type on the interfacial properties of mortars. Interfacial debonding was the main failure mode of mortar rubbles. The interlocking strength of aggregate and mortar strongly affected the compressive strength of materials. When basalt was used as the aggregate, I-II composite failure of the deflection crack occurred as well as interfacial debonding. The highest instantaneous AE energy of the granite mortar rubble was 1349 mV·ms, which was 4.1 times greater than that of the basalt mortar rubble (326 mV·ms). Acoustic emissions of mortar rubble were strongest in the 150–220 kHz range and gave an early warning of the damage load at high frequencies (160–320 kHz). The C-S-H gel formed by the hydration reaction adhered to the aggregate pores and exhibited a “root pile” effect that improved the bonding performance of the interfacial zone. The interfacial porosity of the basalt, granite and limestone mortar rubble was 21.29%, 18.70% and 30.0%, respectively. The limestone interface has a large porosity, the fractal cones was small (1.19), and there was an obvious sidewall effect, but the interfacial strength was weak. The pore structure had a significant effect on the interfacial bond strength. This multi-faceted analysis truly reflected the state and evolution of the damage of mortar rubbles, and the results were very effective for determining the mechanical mode of damage of mortar rubbles.