A laboratory experiment on salt weathering was carried out under changing humidity conditions. Three types of rock (tuff and dense and porous sandstone) with sodium chloride, sodium sulfate, or magnesium sulfate were subjected to humidity oscillations from 20%RH to 98%RH during 6 h periods at 20 °C. Prior to the weathering experiment, the rock specimens were oven-dried, and the water supply was restricted to only that from the air during the experiment. Salt on the rock specimens was deliquesced/hydrated at almost 100%RH during the high-humidity period and crystallized/dehydrated during the low-humidity period. Sodium chloride, which has high deliquescence ability, caused the most intensive weathering. Porous sandstone with sodium chloride was completely broken down after 100 cycles of humidity changes. The other two types of rock with sodium chloride showed flaking or swelling on their surfaces. For dense sandstone with sodium chloride, the Equotip rebound value decreased as the humidity cycles increased. Sodium chloride has a high susceptibility of deliquescence at humidities of more than 80%RH. Weathering by sodium chloride would occur extensively on the surfaces of stone heritages and geoheritages in humid coastal spray zones. Magnesium sulfate induced a weight loss in porous sandstone, flaking from the surface of tuff, and cracks on the surface of dense sandstone. Sodium sulfate had almost no effect in the humidity-change experiment, although salt efflorescence was obvious. The results for magnesium sulfate, salt deliquescence, hydration, and crystallization in the humidity-change experiment were easily repeated. Magnesium sulfate might have more influence than sodium sulfate when air humidity fluctuates in a short period.

中文翻译：

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湿度变化对盐的风化作用的室内实验：潮解和水合作用引起的盐害

在变化的湿度条件下进行了盐风化的实验室实验。在20°C的6小时内，将三种类型的岩石（凝灰岩和致密且多孔的砂岩）与氯化钠，硫酸钠或硫酸镁进行了从20％RH至98％RH的湿度振荡。在进行风化试验之前，先将岩石样品烘干，然后在试验期间将水的供应限制为仅来自空气。高湿度期间，岩石标本上的盐会在几乎100％RH的条件下水化/水合，而在低湿度期间会结晶/脱水。具有高潮解能力的氯化钠引起了最强烈的风化。湿度变化100次后，含氯化钠的多孔砂岩被完全分解。其他两种含氯化钠的岩石在其表面均显示出剥落或膨胀。对于含氯化钠的致密砂岩，随着湿度循环的增加，Equotip回弹值降低。氯化钠在超过80％RH的湿度下具有很高的潮解敏感性。氯化钠的风化将广泛发生在潮湿沿海喷雾区的石头遗产和地质遗产的表面上。硫酸镁使多孔砂岩失重，从凝灰岩表面剥落，在致密砂岩表面产生裂缝。硫酸钠在湿度变化实验中几乎没有影响，尽管盐的起伏很明显。湿度变化实验中硫酸镁，盐的潮解，水合和结晶的结果易于重复。