Mineral phases in an activated kaolinitic waste blended cement system

[EN] Addition of pozzolans to blended cements is well known to have a positive effect due to the pozzolanic reaction. For some pozzolanic materials such as clays, the activation temperature plays an important role in the mineralogy and in the pozzolanic reaction. This paper reports the influence of the activation conditions (700 to 800 °C for 2 or 5 h in a furnace) of a clay waste on the mineralogy of a 20% blended cement matrix at 28 days of normalised curing. The mineralogical composition changes were analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM) — energy dispersive X-ray spectroscopy (EDX). The presence of an unstable LDH-like compounds (without magnesium) and the presence of tetracalcium aluminate hydrate (C4AH13) and calcium hydroxide, and the persistence of alite (Portland cement compound), was identified.