Influence of calcined diatomite content and elevated temperatures on the properties of high strength mortars produced with basalt sand

In this paper, the effect of calcined diatomite (CDT) content on the mechanical, microstructural, and mineralogical properties of high strength mortars (HSMs) exposed to 25, 400, 600, 800, and 1,000°C temperatures is investigated. The percentages of CDT that replace Portland cement (PC) in this work are 0, 5, 10, 15, and 20%, by weight. The researched properties of the HSMs are the unit weight (Uw), ultrasonic pulse velocity (Upv), flexural strength (fs), compressive strength (fc) and the analyses of X-ray powder diffraction, polarized light microscopy, and scanning electron microscopy/energy dispersive spectroscopy. The experimental results show that the CDT has a potential to be successfully employed as a partial replacement of PC in the HSMs exposed to elevated temperatures. The optimal replacement level of PC by CDT is determined as 15% from strength tests. Besides, the Uw, Upv, fs, and fc values progressively reduce as the temperatures subjected to the HSMs increase. The CDT has a positive effect on the fs and fc values the HSMs after exposure to elevated temperatures