• The coefficient of thermal expansion (CTE) of granite is strongly rate-dependent, challenging conventional static CTE assumptions.
• Faster heating rates significantly amplify strain localization and damage accumulation in granite, especially around the quartz phase transition at ~573°C.
• Numerical simulations show that using dynamic CTE (530°C/min) accelerates microwave-induced rock failure area (1000 mm2) by 11 times compared to quasi-static CTE (5°C/min).
• The study provides a scientific basis for optimizing thermal fracturing technologies such as microwave-assisted rock breaking.