A new method of enhancing cement-aggregate interfaces, I. Ideal aggregate and its effects on interfacial microstructures

A concept of an "ideal aggregate" consisting of a hydraulic surface layer and an inert core was proposed to develop a new method of improving cement-aggregate interface in concrete. Such hydraulic layers have been produced on the surfaces of corundum particles by solid-phase reaction of corundum particles with calcium carbonate powder at high temperature with the aid of calcium sulphate as mineralizer. The mineral composition and distribution in the hydraulic layer were examined with XRD and EDAX. The mistrostructure of the ideal aggregate(corundum with hydraulic layer)-cement paste interface was investigated in comparison with those of portland cement clinker, corundum without hydraulic layer and quartz-cement paste interfaces by using electrical conductivity methods and SEM/EDAX techniques. Porosities and pore size distributions of mortars containing these aggregates were determined by mercury intrusion method. The experimental results indicate that interfacial microstructure is substantially densified by using "ideal aggregate" due to hydration of the hydraulic surface layer.