Alkaline activation of metakaolin–fly ash mixtures: Obtain of Zeoceramics and Zeocements

Abstract

This study examines the variation in physico-mechanical properties and mineralogical and microstructural characteristics of the alkaline inorganic polymers obtained by alkaline activation, with a mixture of sodium silica solution and sodium hydroxide, of two different starting materials: matrix M (metakaolin) and matrix FM (50% fly ash and 50% metakaolin). The activation process was conducted at different temperatures (85 °C, 150 °C, and 200 °C). The highest strength values were obtained for the FM matrix at 150 °C. The main reaction product was a sodium aluminosilicate gel in every case. Zeolites formed as by-products. The quantity and type of arising zeolites (sodalite, zeolite A, and faujasite) depended on the nature of the starting material and on the curing conditions used.