Performance of Cement Mortars Containing Clay Exposed to High Temperature

The partial substitution of ordinary Portland Cement (OPC) with clay minerals as supplementary cementitious materials has been currently considered as an effective approach for reducing the harmful environmental impact and health risks of OPC. Although cement mortars are not easily ignitable, the exposure to elevated temperatures can alter their microstructure, leading to reduction in the strength and damage. Therefore, improving the temperature resistance of the cement mortars through the incorporation of local clay minerals has been proposed in this study. The mechanical performance and physical properties of cement mortars containing Wasia Formation clay (WFC) exposed to 700 °C have been investigated. OPC was partially replaced with WFC at various mass ratios of 0, 5, 10, 15, and 20 wt%. Several methods were used to assess the physico-mechanical and structural properties such as compressive strength testing, ultrasonic pulse velocity (UPV), Schmidt hamme, scanning electron microscopy, and X-ray powder diffraction (XRD). The addition of WFC as partial replacement of the cement showed a significant enhancement in the compressive strength for the mortars exposed to normal and elevated temperatures. The compressive strength of the mortar incorporating 20 wt% of WFC and exposed to 700 °C is about 2.5-fold greater than that of the ordinary mortar. Even after exposure to 700 °C, the UPV for the 20 wt% WFC-blended mortar is 30% greater than that for ordinary mortar, indicating the improved structural integrity of the blended mortars. The WFC-blended mortars showed dense and compact microstructure confirming the improvement in the strength of mortars.