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[MIS04-P02] Changes in the physical properties of cultural stones induced by thermal cycling.
キーワード：Thermal weathering、Cultural stone、Leeb rebound hardness、Ultrasonic pulse velocity
As global warming progresses, the deterioration of stone materials due to insolation is becoming an increasingly important issue. In particular, how will any increases in diurnal or annual temperature differences affect cultural stones (e.g., stone monuments, stone-clad historical buildings, statues, reliefs on rock faces)? We investigated this question experimentally by subjecting the samples of granite, marble, and sandstone (which are commonly used as stone materials) to thermal cycles. The samples were repeatedly subjected to temperature changes from 4℃ to 84℃ at a change rate of ±2℃/min for 144 cycles. Physical changes were assessed via the measurements of Leeb rebound hardness (LRH) and ultrasonic pulse velocity (UPV) at certain intervals. Results show an initial UPV decrease after four cycles. However, after all 144 cycles, the UPV measurements showed increases of approximately 25% for granite and marble and approximately 7% for sandstone, relative to intact stone samples. Further, only a small change was observed in the LRH for all samples. These results suggest that internal structural changes in stone materials induced by thermal cycling may be subtle and complex.