Microstructure Influence on The Response of Granitoids to Thermal Shock

Granite rocks are widely used in many construction fields and investigate about preexistent or induced microcracks in them had been the subject of many researches. Since the rock thermal properties is affected by thermal properties of all constituent minerals of the rock, in the microscopic thin sections study, assembled effect of them is showed as microcrack creation. In this study, microcrack induction was performed in three coarse-grained granite samples using heat in the furnace and then shock with cold water. Microcracks in fresh and shocked samples at 250, 450, 650, and 850 Cᵒ was investigated using macroscopic core samples, thin sections, SEM images and crack density measurements in three spatial directions perpendicular on each other. Examination of microscopic sections showed that grain in the same size and variety of boundaries cause the microcrack network not to expand. Myrmikite texture accelerates the development of transgranular microcracks. Some minerals such as mica and amphibole have a specific effect on how cracks develop so they are the beginning or ending of microcracks. Examination of microscopic thin sections showed that different type of microcracks in different samples develop in a different way, which is also affected by the absolute age of the rock. Plagioclase has the least and orthoclase has the most number of microcracks. In 250 and 450 Cᵒ thermal shocks, development of microcracks is also affected by porosity.