Thermal and freeze-thaw-induced degradation of limestone: A comprehensive study on physico-mechanical properties

This manuscript thoroughly investigates the effects of temperature variations on the physico-mechanical properties of limestone taken from the Nowshera formation in northwestern Pakistan. The rock samples were subjected to heat treatment at various temperatures, ranging from 150 °C to 600 °C for 24 hours. Additionally, the samples underwent freeze-thaw cycles, alternating between room temperature and -40 °C, with each cycle lasting 8 hours (4 hours of freezing followed by 4 hours of thawing). Both destructive tests (uniaxial compressive strength, point load index) and non-destructive tests (specific gravity, ultrasonic pulse wave velocity, porosity, and water absorption) were performed to evaluate the rocks' responses to these temperature variations. The density of induced fractures was calculated at the investigated temperatures and after 50 and 100 freeze-thaw cycles. The results indicate reductions in uniaxial compressive strength (UCS), specific gravity, ultrasonic pulse velocity (UPV), and point load (PL) strength with increasing temperature or number of freeze-thaw cycles. After thermal treatment at 600 °C, UCS decreased by 71 %, point load strength by 74 %, UPV by 49 %, and specific gravity by 7.8 %. Similarly, after 100 freeze-thaw cycles, these properties decreased by 23 %, 19%, 15%, and 2.6%, respectively. Conversely, fracture density, porosity, and water absorption increased with elevated temperatures and freeze-thaw cycles. At 600 °C, increases of 2.51 % in fracture density, 66.5% in porosity, and 67% in water absorption were observed. Additionally, after 100 freeze-thaw cycles, these properties increased by 1.44 %, 10 %, and 12.8 %, respectively. Significant changes in all properties were noted when the temperature exceeded 300 °C or the number of freeze-thaw cycles surpassed 50. These findings highlight the degradation of rocks and alterations in their physico-mechanical properties due to thermal variations, which have important implications for industries such as mining and construction.