16:15 〜 16:30
[MIS05-04] Weathering mechanism of limestones submitted to a combination of freezing and salt crystallization
キーワード：Limestone, Salt weathering, Freezing, NaCl
Eight different types of limestone from two quarries in the Jurassic formation of the Paris
Basin used as building stones like poolside were studied. Aging tests, combining experiments of salt crystallization using sodium chloride solutions and freeze-thaw cycles, were performed to compare their behavior and thus their suitability to be used poolside. Their porous networks were first characterized through water total porosity, mercury injection porosimeter, colored thin sections, and capillary absorption. The dried 5cm x 5cm x 5cm specimens were submitted to 15 cycles of 24 hours including immersion in a saturated solution of NaCl for 3 hours, freezing at -18°C for 3 hours, an immersion in distilled water at 20°C for 2 hours to thaw, and then drying in an oven at 65°C for 16 hours. During each process, weights were measured. Every 4 cycles, photographs were taken, and P-wave measurements and color tests were performed.
The results showed that the stones affected by this weathering process had a high
percentage of pore diameter of less than 0.1 μm The calculation of the Salt Susceptibility
Index (SSI, Yu and Oguchi, 2010) of these limestones showed a good correlation between
the index and the experimental results. It confirms that microporosity is one of the main
factors in the susceptibility of stones to salt weathering, rather than the total porosity.
SSI = (IPc + 1Pm0.1)(Pm5/Pc)
Basin used as building stones like poolside were studied. Aging tests, combining experiments of salt crystallization using sodium chloride solutions and freeze-thaw cycles, were performed to compare their behavior and thus their suitability to be used poolside. Their porous networks were first characterized through water total porosity, mercury injection porosimeter, colored thin sections, and capillary absorption. The dried 5cm x 5cm x 5cm specimens were submitted to 15 cycles of 24 hours including immersion in a saturated solution of NaCl for 3 hours, freezing at -18°C for 3 hours, an immersion in distilled water at 20°C for 2 hours to thaw, and then drying in an oven at 65°C for 16 hours. During each process, weights were measured. Every 4 cycles, photographs were taken, and P-wave measurements and color tests were performed.
The results showed that the stones affected by this weathering process had a high
percentage of pore diameter of less than 0.1 μm The calculation of the Salt Susceptibility
Index (SSI, Yu and Oguchi, 2010) of these limestones showed a good correlation between
the index and the experimental results. It confirms that microporosity is one of the main
factors in the susceptibility of stones to salt weathering, rather than the total porosity.
SSI = (IPc + 1Pm0.1)(Pm5/Pc)