Moisture Transport Across Interfaces Between Autoclaved Aerated Concrete and Mortar

Abstract

Experiments were carried out to study the moisture transport across bonded or natural contact interface between autoclaved aerated concrete (AAC) and mortar. Bonded contact, in the present study, refers to the contact between two building materials involving penetration of pore structure with a bonding agent, while natural contact refers to the good physical contact between two building materials without penetration of pore structure. The moisture content profiles were measured using gamma ray spectrometer. The experimental results showed that, for both types of contact, the assumption of imperfect hydraulic contact is more appropriate than the widely used assumption, perfect hydraulic contact. Furthermore, the latter assumption may result in significant error in predicting moisture transport. The mismatching resistance was assumed in the study to explain the impact of imperfect hydraulic contact on the moisture transport. In addition, a numerical model was developed to calculate the moisture transport in multilayered materials and was applied to estimate either the mismatching resistance of the interface or the resistance of air films. For a specimen without an interface, the agreement between model prediction and experimental results was good. It was found that mismatching resistance of the interface varied with moisture content, the type of source material, and the interface with the sink material. This study indicates that the bonded interface can be approximately treated as the natural contact interface, while the presence of an air gap between AAC and AAC could significantly increase the resistance to moisture transport from one material to another.