Calcined clays as supplementary cementitious materials: A comparison between palygorskite and kaolinite

This study aims at investigating the potential as SCM of palygorskite by comparison of calcination and reactivity with kaolinite. The physico-chemical modifications after calcination were investigated by XRD, 27Al and 29Si MAS NMR analyses, then the reactivity study and mechanical performance measurements were assessed. The results detailed that palygorskite behaves quite differently from kaolinite during calcination. Dehydroxylation kinetics is longer and gradual dehydroxylation is observed for palygorkiste and associated with progessive evolution of Al and Si environment leading to the formation of silica-rich aluminium-poor domains. The study showed a significant increase of mechanical performance on pastes incorporating only 10 % of calcined palygorskite in comparison to the reference which indicates that calcined palygorskite can be a suitable SCM once calcined.