Microcracks play an essential role in controlling rocks’ physical and mechanical properties and thus are a vast research subject in engineering geology. The present study aimed to investigate microcracks developed in granitoids. Thermal shock at four temperatures of 250, 450, 650, and 850 was applied to induce microcrack in granitoids. The rate of microcracks development and their effect on the physical properties of the rocks were assessed using the measurement of the P-waves velocity and capillary water absorption test. Both tests showed that the thermal shock, even in one cycle, has developed micro cracks. Moreover, the increased rate in effective porosity and total porosity of granitoids due to the growth of microcracks would estimate by the capillary water absorption test. This study showed that microcracks development directly relates to the increase in temperature at the thermal shock. The capillary water absorption test could measure the granitoids porosity as well as the water absorption and retention in the induced microcracks. These two tests could investigate microcracks development from two different points of view. The p-wave velocity estimates the propagation of different types of microcracks, while the capillary absorption test evaluates the connected microcracks. The effective porosity differently affects the rock mass efficiency in varied projects. Finally, total porosity and effective porosity are developed independently of each other through thermal-induced micro-cracks
