•Presenting the relationship between fracture toughness and the number of freeze–thaw cycles.•Presenting the relationship between fracture toughness and freezing temperature.•Analysis of X-ray CT to ...investigate the damage caused by the freeze–thaw cycles.
The freeze–thaw process is one of the natural phenomena significantly affecting the characteristics of rocks and their properties. This study aimed at investigating the effects of freeze–thaw cycles and freezing temperature on mode I and mode II fracture toughness of Lushan sandstone. To this end, specimens were exposed to 0, 5, 10, 20 and 30 freeze–thaw cycles, and mode I and mode II fracture toughness were evaluated in different cycles. The effect of freezing temperature in a freeze–thaw cycle on mode I and mode II fracture toughness was also investigated. X-ray computerized tomography (CT) was used to determine specimen damages caused by freeze–thaw cycles. According to the results, mode I and mode II fracture toughness nonlinearly decreased with increasing the number of freeze–thaw cycles. The CT photographs showed an increase in the damage factor caused by freeze–thaw cycles. The mode I and mode II fracture toughness of Lushan sandstone nonlinearly decreased with increasing the freezing temperature in the freeze–thaw process.
•Investigating the effect of the confining pressure and the temperature on the mode I and mode II fracture toughness of cement mortar.•Presenting the relationship between the mode I and mode II ...fracture toughness and the confining pressure for cement mortar.•Presenting the relationship between the mode I and mode II fracture toughness and the temperature.
The effects of temperature and confining pressure were investigated on the mode I and mode II fracture toughnesses of Cracked Chevron-Notched Brazilian Disc (CCNBD) cement mortar specimens. The specimens were tested at ambient temperature (20 °C), as well as 60, 100 and 150 °C to study the effects of temperature. Furthermore, CCNBD cement mortar specimens were tested under 0, 3, 5, 7, and 10 MPa to investigate the effect of confining pressure on fracture toughness. Cement mortar specimens were used for testing in this study. According to the results, both mode I and mode II fracture toughnesses of the cement mortar increased linearly with increasing the confining pressure. Mode I and mode II fracture toughnesses initially increased by increasing the temperature up to 60 °C but then decreased as the temperature was elevated to the 100–150 °C range.
