Effects of calcination and milling pre-treatments on natural zeolites as a supplementary cementitious material

Abstract

In this research, the effects of calcination and conventional milling, individually and as a combination of pre-treatments, on the pozzolanic activity of natural zeolites were analyzed and evaluated. The characterization of the material was done by techniques such as fluorescence and X-ray diffraction, thermogravimetric analysis, particle sizes distribution, Brunauer-Emmett-Teller (BET) - specific surface area, and porosity. Calcination was performed at 300, 600, and 800 °C for 5 h. Conventional milling was carried out to raw zeolites and after calcination in a ceramic ball mill for 3 h. Pastes and mortars with replacement percentages of 30, 40, and 50% were prepared for evaluating the pozzolanic activity, compressive strengths, and the reaction rate of the natural zeolite type mordenite and heulandite-clinoptilolite present in the material. It was found that the pozzolanic activity of natural zeolites increases for each pre-treatment separately and together after 8 days of hydration. The most effective individual pretreatment was grinding, but pretreatments as a combination bring many benefits such as the higher increase in compressive strength and non-agglomeration of the material in the mill.