Investigation of the effects of two different cooling treatments on the physico-mechanical and microstructural properties of granite after high temperatures

Granite deposits have a strategic importance due to the energy developments in Türkiye and its stability plays an important role in environmental safety. Therefore, it is of major importance for engineering practice to investigate the thermal damage mechanisms in the case of high temperature exposure effects. This study discusses the results of tests performed to investigate the physico-mechanical and microstructural properties of granite after exposure to high temperatures and two different cooling treatments. The samples, which were previously heated from 24 to 1000 °C temperatures and then cooled in an oven or water, were tested in terms of porosity, hardness, P–S wave velocity, uniaxial compressive strength, point load strength index (Is50) and microstructure. The Yaylak granite of Türkiye has been examined for the suggested research. The results show that the water-cooled granite samples exhibited higher decreases in P–S wave velocity, hardness, and uniaxial compressive strength compared to the oven-cooled samples. In addition, porosity values were increased in water-cooled granite samples. With scanning electron microscope and polarizing microscope analysis, the microcrack density and width in water-cooled granite samples increased more with high temperature, while they increased less in oven-cooled granites. The disintegration of the water-cooled granite samples increased considerably at 1000 °C and measurements could not be taken at this temperature. At the same temperature, water-cooling treatment caused microcracks and micropores, which led to more critical damage to the granite. These conclusions verify that different cooling methods have several effects on the physico-mechanical and microstructural properties of granite, and ensure a foundation for the prediction of rock mass behaviors in situations with high temperature exposure effects (e.g., geothermal exploration and nuclear waste disposal).