Thermal Effects on the Structural and Mechanical Microstructure Parameters of Siliceous Sandstone from Kielce Upland

This study explores the thermal evolution of the microstructure and mechanical properties of Jurassic sandstone from the Kielce Upland, subjected to temperatures between 20°C and 1000°C. Combining microcomputed tomography (micro-CT) and nanoindentation techniques, it analyzes how geometric changes affect mechanical parameters. Key features like porosity, pore size distribution, and solid matrix thickness were assessed alongside indentation modulus (MIT) and hardness (HIT). The results reveal a strong correlation between microstructural changes and mechanical responses. At 200°C, microstructural compaction and thermal tightening lead to temporary strengthening. Above 600°C, increased porosity, microcrack formation, and rock matrix degradation cause significant reductions in mechanical properties. Reconstructed grayscale values are identified as reliable estimators for mechanical property changes, particularly for indentation modulus, when baseline parameters are available.