Slate is a natural stone widely used for building, for which is subjected to regulations and standards in order to be commercialized. As far as the influence of water is considered, only detailed studies are compulsory when the water absorption is higher than 0.60%. However, the mechanical behavior of this layered material depends on water content, which is function of the relative humidity of the environment, and not considered in existing standards. In order to investigate its influence on foliation tensile strength, an experimental study was performed, which consists on carrying out Brazilian tests in slate samples with known water content, applied and controlled by using vapor equilibrium technique. This technique allows controlling the relative humidity of the environment surrounding the material and that of the air on its pores. Relative humidities between 55% and 92% were applied during the tests and defined considering climate data from the north of Spain. Despite the maximum water content tested in the slates was low (0.10%) in comparison with its saturation content (0.57%), the experimental results show a decreasing of the foliation tensile strength that reaches up to three times less with an increment of the environmental relative humidity of 37%. The results achieved can be important in order to quantify the layering weakness due to a natural alteration factor such as the environmental relative humidity. Moreover, the procedure employed is proposed as a convenient method for adequating each variety of slate stone to different climates according to its vulnerability to water.

中文翻译：

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环境相对湿度对板岩层状抗拉强度的影响

板岩是一种广泛用于建筑的天然石材，必须遵守相关法规和标准才能商品化。就水的影响而言，只有当吸水率高于0.60％时才需要进行详细研究。但是，这种层状材料的机械性能取决于含水量，而含水量是环境相对湿度的函数，在现有标准中并未考虑。为了研究其对叶面抗张强度的影响，进行了一项实验研究，该实验包括在已知水含量的板岩样品中进行巴西测试，并使用蒸汽平衡技术对其进行控制。该技术允许控制材料周围环境的相对湿度和其孔上空气的相对湿度。在测试过程中，相对湿度在55％到92％之间，并根据西班牙北部的气候数据进行了定义。尽管在板岩中测试的最大水含量与其饱和含量（0.57％）相比较低（0.10％），但实验结果表明，随着环境的增加，叶面抗张强度降低了三倍之多。相对湿度为37％。为了量化由于自然变化因素（例如环境相对湿度）引起的分层缺陷，获得的结果可能很重要。此外，提出了所采用的程序，作为一种方便的方法，可根据其易受水的影响，使各种板岩适应各种气候。