Effect of environmental relative humidity in the tensile strength of layering in slate stone

Evaluation of mechanical weakening of calcarenite building stones due to environmental relative humidity using the vapour equilibrium technique

“…Significant decreases of E st (around 50-75%) were also reported in mudstones when RH increased from 21-32 to 99% (Pham et al, 2007;Wang et al, 2015). In addition, the reductions of BTS found in calcarenites were in consonance with those obtained in slates by Garcia-Fernandez et al (2020), who reported a drop of 67% when RH increased from 55 to 92%. Additionally, the fact that the existing regulations for the commercialization of these materials do not consider this phenomenon and are mainly focused on determining its vulnerability to weathering processes (like salt crystallization, atmospheric pollutants or freeze-thaw cycles) suggests the need for developing specific standards to assess the sensitivity of the mechanical parameters of building stones to the environmental RH.…”

“…The variation of the abovementioned mechanical properties (UCS, E st , BTS and I s( 50) ) with the environmental RH were well fitted through linear functions for the three calcarenites, which is in line with the results reported in some cited previous works (Garcia-Fernandez et al, 2020;Yang et al, 2012).…”

“…Furthermore, from the first stage it is possible to calculate the water absorption coefficient (A w ), defined as the gradient of the straight line obtained by plotting the cumulative mass of water absorbed per unit area versus the square root of storage time. In this connection, despite A w is frequently calculated by capillary tests (AENOR, 1999), it can be also applied for the samples exposed to VET with the purpose of represent the velocity of water absorption, which is related with the permeability to water of the geomaterial, considering its non-saturated condition (Garcia-Fernandez et al, 2020). Specifically, the obtained A w values were 0.26, 0.40 and 0.27 kg•m -2• h -0.5 for G-1, G-2 and G-3, respectively.…”

“…In both cases, the saturation mechanism of the specimens is carried out through the penetration of water in the liquid form within its pore network, and therefore the nearby decay processes to this mechanism could be the saturation by rainwater infiltration or by groundwater level rise. However, the water transference between the environment and the stone materials frequently occurs in vapour form when changes in the relative humidity of the air involve variations in the moisture content of stones until reaching the corresponding new equilibrium (Garcia-Fernandez, Alvarez-Fernandez, Cardoso, & Gonzalez-Nicieza, 2020). Particularly, according to Franzen and Mirwald (2004) the transport and distribution of fluid water and vapour in porous stone occurs by means of the following steps.…”

Slate–Cork Laminate Enhanced with Silicone for Habitat Industry Application

“…Similarly, slate used for facades must exhibit sufficient mechanical strength to withstand minor impacts. However, moisture present in the environment can penetrate between the layers of slate through capillary action [17]. An increase in relative humidity from 55% to 92% reduces its mechanical strength to one-third [17].…”