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The knowledge of moisture migration inside building materials and construction building components is decisive for the way they behave when in use. The durability, waterproofing, degrading aspect and thermal behaviour of these materials are strongly influenced by the existence of moisture within their interior, which provoke changes in their normal performance, something that is normally hard to predict. Due to the awareness of this problem, the scientific community have per-formed various studies about the existence of moisture inside porous materials. The complex aspects of moisture migration phenomenon tended to encompass monolithic building elements, since the existence of joints or layers contributes to the change of moisture transfer along the respective building element that contribute to the change of mass transfer law. The presentation of an experimental analyses concerning moisture transfer in the interface of material that makes up masonry is described in such a way as to evaluate the durability and/or avoid building damages.

In this work it was analysed, during the wetting process, the influence of different types of interface, commonly observed in masonry, such as: perfect con-tact, joints of cement mortar, lime mortar, and the air space interface. The results allow the calculation of the hygric resistance. With these results, it is possible to use any advanced hygrothermal simulation program to study the water transport in building elements, considering different interfaces and their hygric resistance.

Table of Contents

Frontmatter

Chapter 1. Introduction

Abstract
Moisture damage is one of the most important factors limiting building performance. High moisture levels can damage construction (condensations, mould development) and inhabitants’ health (allergic risks). As an example, rising damp coming from the ground that climbs through the porous materials constitutes one of the main causes of buildings degradation; especially the old ones.
João M. P. Q. Delgado, António C. Azevedo, Ana S. Guimarães

Chapter 2. State-of-the-Art

Abstract
Transport phenomena in porous media occurs in diverse fields of science and engineering, ranging from agricultural, biomedical, building, ceramic, chemical, and petroleum engineering to food and soil sciences. Morrow provides an extensive description of the problems involving porous media. For building engineering, obtaining a good understanding of moisture transport in building envelopes is becoming one of the most important tasks. In the last few decades, many studies investigating moisture transport in building envelopes have been published, which have helped to improve overall building envelope design. This chapter presents a brief review of these studies.
João M. P. Q. Delgado, António C. Azevedo, Ana S. Guimarães

Chapter 3. Moisture Content Determination

Abstract
Building materials are, for the most part, porous structures which generate permanent changes when in contact with moisture, which could be in the vapour phase and in the liquid phase, with the environment in which they are placed. This behaviour conditioned their properties and their durability. It should be noted that humidity is a major cause of the pathologies observed in buildings. The profile of the transient moisture content describes moisture content as a function of time and place. This profile is essential for determining the moisture diffusivity of a material and is also important for studying the interface phenomena. In this sub-chapter, a brief description of the most important experimental transient methods—Gravimetric Method, Nuclear Magnetic Resonance (NMR) method, X-Ray Analysis and Gamma Ray attenuation method—to determine moisture content profiles is going to be presented.
João M. P. Q. Delgado, António C. Azevedo, Ana S. Guimarães

Chapter 4. Interface Influence During the Wetting Process

Abstract
As it was previously said moisture damage is one of the most important pathological causes of building materials and components. A moisture measuring device based on a non-destructive method of gamma rays attenuation allows measuring this damage to broaden concepts in building physics related to moisture transfer; study the influence of the interface between layers in moisture transfer; analyse the influence of gravity on absorption and drying of different types of building materials; study the kinetics of absorption and drying of walls of one or more layers; analyse the importance of the temperature gradient in the movement of moisture; and calculate the coefficient of water diffusivity of some building materials, etc.
João M. P. Q. Delgado, António C. Azevedo, Ana S. Guimarães

Chapter 5. Conclusions

Abstract
Moisture transport through a building envelope normally involves interface phenomena, i.e., moisture transport across interfaces between building materials. Therefore, the knowledge of the interface phenomena is essential for the prediction of moisture behaviour in a building envelope. Most hygrothermal models treat materials as individual layers in perfect hydraulic contact, i.e., the interface has no effect on the moisture transport. However, in practice, this might not always be true. Therefore, to appropriately evaluate the performance of a building envelope on moisture transport that lead to building envelope design guidelines, it is imperative to obtain a good understanding of the interface phenomena. The most common types of interfaces are: “Hydraulic contact” when there is an interpenetration of both layer’s porous structure; “Perfect contact” when there is a contact without interpenetration and “Air space” between layers when there is an air box of a few millimetres wide between the layer’s porous structure.
João M. P. Q. Delgado, António C. Azevedo, Ana S. Guimarães
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