Dolomite Under Thermal Cycling: Strength, Deformation, and Microstructural Evolution Under Different Loading Modes

ABSTRACT This study investigates the effect of thermal cycling and loading modes on the fracture behavior of dolomite, a strong magnesium‐rich rock. Forty‐eight dolomite specimens (semicircular bend [SCB] and intact Brazilian disks) were subjected to 0, 50, 100, and 500 heating–cooling cycles between 20°C and 60°C and then tested under Pure Mode I, Mixed Mode I/II, and pure Mode II loading conditions. Results indicated that thermal cycling enhanced dolomite's strength properties—fracture toughness, fracture speed, and acceleration—up to ~300–400 cycles, after which these properties deteriorated. These changes correlated with variations in sound wave velocity and porosity, suggesting microstructural alterations. Intact Brazilian disks showed tensile strength and fracture toughness comparable to SCB specimens under Pure Mode I but demonstrated a higher tensile modulus across all loading conditions. A direct correlation was observed among fracture load, absorbed energy, fracture velocity, and fracture toughness, with faster fracture associated with higher toughness.