Microcracking in impact-damaged granites heated up to 600 °C

The acoustic emission (AE) technique was applied for monitoring the high-speed cracking process in three kinds of impact-damaged granites at temperatures 20 °C to 600 °C. The analysis of the amplitude-frequency response of the AE time series showed the presence of a few populations of cracks differing in size in the range 0.25 mm to 2.3 mm. The dependence of the appearance/growth/decay of any given population on temperature and physical and mechanical properties of granites evidenced the interplay between inter- and intragranular cracking under various thermal conditions. At room temperature (pure mechanical forcing), the intergranular damages along boundaries between the same minerals prevail; at 200 °C (impact forcing plus thermoelastic stress), the cracking between grains of quartz and feldspar emerge; finally, in the range 500 °C to 600 °C, the intragranular damages appear. (paper)