Thermal properties of Central Aare granite for temperatures up to 500 degree C: Irreversible changes due to thermal crack formation

Thermal diffusivity, heat capacity, and thermal conductivity of Central Aare granite are reported in the temperature range from 25 degree C to 500 degree C. Each rock sample underwent three consecutive heating and cooling cycles. Significant irreversible changes in the properties due to thermal crack formation could be observed. After the first thermal cycle, both thermal diffusivity and conductivity dropped to about 75% of the initial value at room temperature, whereas the heat capacity did not show an irreversible decay. For subsequent thermal cycles, no further permanent changes of the investigated properties could be observed. From the conducted measurements, accurate correlations are derived, offering a platform for precise high-temperature experiments and other research on Central Aare granite and similar granitic rocks. The report shows that the assumption of constant thermal properties leads to significant inaccuracies at elevated temperatures, especially if thermal cycles are present. Key Points * Thermal properties of Central Aare granite are reported over the temperature range from 25 degree C to 500 degree C * Irreversible changes in the properties are observed and could be attributed to thermal cracking * Accurate correlations are provided for the first heating phase and for subsequent thermal cycles