The influence of mixing on the microstructure of the cement paste/aggregate interfacial zone and on the strength of mortar

Abstract

The influence of mixing on the microstructure of the cement paste/aggregate bond has been investigated. Back-scattered electron microscopy was used in conjunction with quantitative image analysis to examine the microstructure of the interface between limestone aggregate and the cement matrix in a series of mortars. The distribution of porosity and anhydrous material along the paste/aggregate interface was shown to be dependent upon the relative abundance of water at the aggregate surface during mixing. Improvements in the interfacial microstructure were shown to correlate with improvements in strength and fracture properties. The interfacial zones seen in the limestone mortars were compared with a model interfacial system. A new classification system for two types of interfacial regions in mortar is proposed.