Relationships between milling input energy and chemical reactivity for mechanochemical activation of clays

Mechano-chemical activation is of rapidly growing interest for producing cementitious constituents from clays. The chemical reactivity of clay minerals is enhanced during intensive grinding, due to mechano-chemical dehydroxylation and mechanically-induced amorphisation. The most widely used grinding apparatus for laboratory-scale studies is a planetary ball mill. It is still largely unknown whether activation efficacy is critically dependent on any individual milling parameter, or whether trade-offs are possible between different parameters. In this study a first principles approach, previously applied to alloy amorphisation, is adopted to estimate the energy of an individual collision event and the total milling input energy. Using a combination of primary data generated through experiments and secondary data from literature, a set of nearly 100 datapoints was analysed. Rapid increases in chemical reactivity were generally observed for