Capillary Absorption into 2-layer Composites Comprising of Natural Stone and Compressed Earth Blocks

Earth masonry usually comprises of alternating layers of materials, with different hydraulic properties. The properties of the different materials inevitably affect liquid movement into the composite. In this study, an experimental investigation of capillary absorption into 2-layer composite building materials comprising of equal size natural stone and Compressed Earth Blocks (CEBs) is carried out. Initially, the capillary absorption test is conducted on 2-layer composites comprising of a higher sorptivity first layer (Sa > Sb). Subsequently, the same specimens are reversed to assess the behavior of the composite when the first layer has a lower sorptivity (Sa < Sb). The results indicate that, in Sa > Sb composites, there are two distinct phases during liquid absorption, each with a different gradient, in line with the theory of capillary absorption into 2-layer composite materials. The second layer always presents a lower gradient of absorption than the first layer. In contrast, in Sa < Sb composites, both layers show almost the same gradient. This appears not to be in line with the theory, which states that the second layer should control the absorption into the composite material. The aforementioned observation may be attributed either to the properties and/or the size of the individual materials hereby tested.