Effect of calcination on the reactivity of natural clinoptilolite zeolites used as supplementary cementitious materials

This study examined several sources of natural clinoptilolite zeolite calcined at temperatures of 300 degrees C-965 degrees C, tracking changes in phase content, particle size, surface area, and pore size distribution. Changes in pozzolanic reactivity with calcination were measured through calcium hydroxide content of hydrated zeolite-cement pastes and compressive strengths of cement mortars. Calcination increased zeolite particle size and reduced porosity and surface area, resulting in decreased zeolite pozzolanic reactivity despite increased amorphous content in the samples. Overall, in contrast to what has been shown previously in literature, calcination was ineffective in increasing the reactivity of clinoptilolite zeolites for use as SCMs. (C) 2020 Elsevier Ltd. All rights reserved.