Macro- and micro-mechanical response and damage mechanism of sandstone under high-temperature conditions

• Temperature alters mineral phase and pore characteristics, jointly affecting sandstone mechanical properties. • A threshold temperature of 600 °C separates low-temperature strengthening from high-temperature damage. • Low-temperature strengthening involves pore and mineral phase strengthening, while high-temperature damage is primarily pore damage. • AE event and energy patterns shift from post-peak surge to stepwise increase, indicating a transition from brittle to tensile failure.