Abstract
Rising temperature will cause the changes of pore characteristics and strength property in rock. This research takes the limestone produced in Taihang Mountains as the research object, and performs high-temperature treatment within 25–1000 °C. The high-resolution X-ray computed tomography (CT) scanning test method is used to visually reconstruct the three-dimensional image of the sample, and obtain the spatial distribution status of the mesoscopic parameters of the bones, pores/cracks, etc. The results show that when the temperature exceeded 700 °C, the samples appeared milky white in appearance and as the temperature increased, the color gradually turned white, macroscopic cracks began to appear on the surface, while the meso-pores connected rapidly, reflecting a typical progressive destruction process from inside to outside. The change law of volume porosity with temperature has a consistent trend with that of the apparent morphology of the sample. Similarly, the mechanical test results suggest that 700 °C is also the turning temperature for strength deterioration and brittle-plastic transformation of sample. Based on the results of high-temperature test, CT test and mechanical test, there are enough evidences to show that, for the limestone sample, 700 °C is probably to be the mutation temperature of physical–mechanical behavior.
Highlights
Rising temperature will cause the changes of pore characteristics and strength property in rock
After standing for 120 h, the sample completely collapsed, and the load-bearing capacity was completely lost in the absence of any external loading, and it degenerated into loose particles only in the natural environment. These results show that high temperature had a huge impact on the microstructural characteristics of the limestone sample, and these effects could not be reflected by the macro test
The pore radius, throat radius and maximum coordination number all increase with the increase of temperature, indicating that high-temperature promotes the development of pores, and improves the connectivity of pores
Summary
Resolution ratio/μm Voltage/kV Electric current/μA Exposure time/s Scanning time/h. was a high-resolution industrial CT, with a detailed resolution exceeding 2 μm, which could be combined with a high-resolution objective lens coupled detector and a large-field flat-panel detector to form a unique dual-optical X-ray imaging detection system. With the increase of temperature to 800–900 °C, the distribution range and shape of pore radius and throat radius did not change significantly, but the proportion of large pores and throats gradually increased, and the maximum coordination number reached 8 and 9, respectively. When the temperature is 1000 °C, the pore radius distribution range extends to [30–80] μm, the throat radius extends to [5–50] μm, and the maximum coordination number further increases to 12. The increase in temperature improves the connectivity of the rock sample to a certain extent
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