Evaluating the thermal-cooling induced effects on the Ambela granite properties (from Pakistan) using experimental and image processing techniques

A series of experiments were conducted on the Ambela granite at predetermined temperatures (25, 300, 600, and 900 °C) for 3 h and cooled under slow and rapid conditions. The experimental results show that as the temperature rises, porosity increases (9.5%), while mass and P-wave decrease by 0.1% and 14.0%, respectively. Furthermore, increasing temperature’s mediated effects on granite damage were significantly higher in rapid cooling, resulting in a decrease of 85% and 88% in uniaxial compressive strength and Young’s modulus, respectively. As this experimental procedure is expensive and time-consuming, therefore, considering the thermal-cooling effects, it is essential to capture these effects using sophisticated and cutting-edge technologies. In this regard, a compound microscope is used for thin section study and based on their results, a novel model is developed. This model is established on watershed segmentation, which is an image processing technique to capture the effect of thermal cooling on the porosity, crack propagation, and damage factor numerically. The model results were validated with experimental results, which give a correlation (R²) value of 0.99% and 0.93% for slow and rapid cooling, respectively. It was also noticed in the cooling that the average crack length initially increased with increases in temperature (25–300 °C) but then decreased from 600–900 °C. In the cooling process, significant changes in crack length were observed in rapid cooling compared to slow cooling.