Characterization and effect of mechanical and thermal activation in mining tailings for use as supplementary cementitious material

Abstract

The objective of this work is to evaluate the potential use of gold and silver tailings (GST) as Supplementary Cementitious Material (SCM). Physical, chemical, and mineralogical characteristics of GST were evaluated. Based on the initial characterization of GST, mechanical and thermal activation were proposed to improve GST reactivity. The effect of both activation processes in crystallite size and Full Width at Half Maximum (FWHM) were determined by X-Ray Diffraction (XRD). Mechanical activation at 140 min of milling and thermal activation at 1000 °C allowed the most significant reduction of crystallite size and particle size. The unconfined compressive strength (UCS) and the Strength Activity Index (SAI) were tested in mortar cubes partially substituted with activated tailings. Results showed that 10, 15, and 20 wt% substitution with activated tailings exceed the 75% SAI according to ASTM standards. Micrographs showed the presence of a calcium silicate hydrate (C-S-H) gel rich matrix in experimental mortars.