Effects of elevated temperatures on strength and microstructure of mortar containing nano-calcined montmorillonite clay

This study focuses on the residual mechanical strengths and microstructure of nano-calcined montmorillonite clay (NCMC) cement mortars at high temperatures. NCMC was prepared via thermal activation of nano-clay, and the produced mortars with 0%, 1%, 3%, and 5 wt% NCMC replacements were subjected to temperatures of up to 900 degrees C. The fire-resistance properties of the produced mortars and their role were analysed through thermogravimetric analysis, X-ray diffraction, and scanning electron microscopy. The results revealed that the use of thermally treated NCMC reduced the density and widths of micro cracks, improved the mass-loss behaviour, reduced the amount of calcium hydroxide crystals, and strengthened the matrix, which explains their higher residual mechanical strengths. (C) 2020 Elsevier Ltd. All rights reserved.