Measurement of aggregate interfacial porosity in complex, multi-phase aggregate concrete: Binary mask production using backscattered electron, and energy dispersive X-ray images

This paper presents for the first time a method for the accurate segmentation of complex (multi-phase) natural aggregate particles, from greyscale backscattered electron images (BEI) of hardened concrete, so that interfacial porosity may be measured. Energy dispersive X-ray (EDX) spectra are collected from phases present in aggregate particles to identify the most abundant and therefore useful elements to be captured during later mapping. Appropriately captured energy dispersive X-ray dot maps are used to progressively construct a multi-phase composite aggregate binary mask, for aggregate particles composed of more than one mineral. The mask image is then re-processed in combination with the backscattered image, to produce an accurate hardened cement paste (HCP) porosity mask, which is used to measure the distribution of interfacial porosity around aggregate particles.