Assessment of the pozzolanic reactivity of slates waste from the Tchihingue deposit in Angola: Influence of the mineralogical composition

ABSTRACT

In the present work, slate rock wastes from the Tchihingue deposit in Angola were assessed as a potential source of supplementary cementitious materials, focused on pozzolanic reactivity and the mineralogical composition of the wastes of yellow and brown slate. Atomic Absorption Spectrometry (EAA) and X-ray diffraction (XRD), respectively were used performed the chemical and mineralogical characterization of uncalcined and calcined slate wastes. Quartz and muscovite are the main phases in both slate wastes. Kaolinite in the yellow slate and hematite in the brown slate were identified as secondary phases. Pozzolanic reactivity through solubility of silica and alumina in alkali and the strength activity index with Portland cement, showed that the calcined yellow slate shows the highest reactivity, which is related to the presence of kaolinite in the sample, as it is the phase most active among clay minerals. The slate wastes evaluated comply with the chemical and physical-mechanical requirements, in accordance with the ASTM C 618 standard, for which reason both calcined wastes are considered to present prospects for use as supplementary cementitious materials.

Keywords
pozzolanic reactivity; cementitious materials; slate waste; slate; pozzolan