Utilization of Mine Tailings Activated with NaOH and KOH for Alkali-Activated Cement: a Strategy for Waste Minimization

Abstract

This study investigates the feasibility of using mining tailings as a precursor material for alkali-activated cement to address both the mitigation of environmental pollution from the disposal of mining industrial waste and the reduction of CO₂ emissions associated with Portland cement production. X-ray fluorescence analyses conducted on mine tailings revealed a chemical composition suitable for the generation of Alkali-activated materials (AAMs). X-ray diffraction analysis showed the presence of crystalline phases of calcite and quartz in the tailings in their natural state. Experiments were carried out to study the effect of two activators, NaOH and KOH, at concentrations of 2, 4, 6, 8, and 10M, mixed with the tailings sample. It was observed that when testing a concentration of 10M of both activators, the characteristic peaks of calcite disappeared, giving rise to portlandite. Additionally, the formation of sodium and potassium carbonates was evidenced, depending on the activator. To evaluate the activation process, tests were conducted with different stirring times, results indicated that 15 minutes of stirring were comparable to 24 hours of agitation. Furthermore, a compressive strength analysis was performed on specimens prepared with a concentration of 10M of both activators, cured at 3, 14, and 28 days. Compressive strength tests yielded results of 16.4 MPa with NaOH and 14.6 MPa with KOH after 28 days of curing, and SEM-EDS analysis indicated geopolymerization processes in the materials.