Effects of high-temperature heating and cryogenic quenching on the physico-mechanical properties of limestone

This paper is designed to investigate the influence of high-temperature heating and cryogenic quenching using liquid nitrogen (LIN) cooling on the physico-mechanical properties of limestone such as compressive strength, tensile strength, ultrasonic pulse velocity (UPV) and morphological characterization. The main aim is to provide a better understanding on influence of the temperature shock including high temperature pre-treatments and combined process with heating followed by LIN quenching on the physico-mechanical properties of rock. The samples were subjected to different thermal treatment using high-temperature of 100 °C, 200 °C, 400 °C and 600 °C for 4 h. In addition, the combined process of heating at 600 °C for 4 h and LIN quenching for 15 min, 30 min, 45 min and 60 min has also been explored. The obtained results indicate that pre-treatments in limestone depict decreasing trend in strength values. Limestone samples show 62% drop in uniaxial compressive strength (UCS) and 84% drop in Brazilian tensile strength (BTS) for 600 °C pre-treatment for 4 h, whereas the decrease in 70% of UCS and 89% of BTS are also observed for the combined process with 60 min of LIN quenching. The influence of pre-treatment on UPV and microstructure of rock has been investigated in detail. Due to thermal stress, very low UPV has been obtained for the pre-treated samples compared to untreated. SEM analysis has been carried out to understand the fracture morphology for both untreated and treated rock samples.