Effect of activation technologies on natural clays reactivity

This study investigates the physical and chemical transformations induced by thermal, mechanical, and chemical activation of three naturally quarried clays with distinct mineralogies to determine the most effective treatment for enhancing cement replacement performance. Thermal activation efficiency depends on mineral-specific dehydroxylation temperatures, whereas mechanical activation, by modifying particle morphology and increasing surface area, shows great potential for mixed-mineralogy clays. Chemical activation with sulfuric acid enhances the reactivity of montmorillonite-rich clays but is hindered by secondary precipitate formation above 3 M. Among all treatments, mechanical activation yielded the highest 28-day strength gains (17-20%) relative to CEM I. While thermal activation remains the most industrially viable, this comparative assessment highlights the interplay between clay composition, activation conditions, and performance, offering practical insights for translating laboratory-scale findings into scalable strategies for sustainable cement production. Mechanically activated clays provided the highest average compressive strength when used in composite cement for all activated clays. Chemical activation appeared more effective than thermal activation for montmorillonite-rich clays. The optimal dehydroxylation temperature for thermally activated clays did not necessarily correspond with the temperature yielding maximum compressive strengths. Chemical activation using sulfuric acid at room temperature was most effective at concentrations > 1M, but for some clays it was limited at concentrations >3M by the formation of precipitates.