Determination of moisture distributions in porous building materials by neutron transmission analysis

The movement of moisture inside building structures can affect them in important ways, causing physical and chemical damage. Therefore the study of moisture transport in porous building materials is highly relevant to a better understanding of the durability of building structures made of porous mat...

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Bibliographic Details
Published in:Materials and structures 1998-05, Vol.31 (4), p.218-224
Main Authors: Pleinert, H, Sadouki, H, Wittmann, F H
Format: Article
Language:English
Subjects:
Building construction
Building materials
Civil engineering
Coefficients
Construction materials
Mathematical analysis
Moisture
Moisture content
Porous materials
Spatial resolution
Studies
Transport
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Summary:The movement of moisture inside building structures can affect them in important ways, causing physical and chemical damage. Therefore the study of moisture transport in porous building materials is highly relevant to a better understanding of the durability of building structures made of porous materials. The moisture transport can be described phenomenologically by a diffusion equation using a moisture content dependent moisture transfer coefficient. To determine the transfer coefficient in a given material, the experimental quantitative measurement of the time and space dependent moisture distribution in the material is necessary. Neutron radiography provides a highly sensitive non-destructive method for the detection of the presence of water and provides high spatial resolution. A new neutron transmission analysis technique has been developed and optimized for the study of moisture in building materials to extract the quantitative information from the experimental data. Typically, moisture contents down to a few mg/cm super(3) can be detected at a spatial resolution of 1 mm. As an application example, the determination of the time and space dependent moisture distribution in a brick sample and the subsequent determination of the moisture transfer coefficient are presented.Original Abstract: Les mouvements d'eau au sein de la structure poreuse d'un ouvrage peuvent l'affecter serieusement, notamment par une degradation physique ou chimique. Aussi est-il necessaire de bien comprendre les mecanismes de transfert d'humidite pour une meilleure maitrise des problemes lies a la durabilite des constructions en materiaux poreux. Les transferts d'humidite sont souvent decrits d'une facon phenomenologique, par des equations de type diffusion, mettant en jeu un ou plusieurs coefficients de transfert. Une methode de determination des coefficients de transfert hydrique d'un materiau consiste a les extraire de l'information contenue dans les distributions spatio-temporelles de teneur en eau mesurees. La radiographie a neutrons s'avere etre une technique de mesure non-destructive de tres grande sensibilite pour detecter la presence d'eau, avec notamment une haute resolution spatiale. Une nouvelle technique d'analyse de la transmission neutronique a ete developpee et optimisee pour l'etude d'analyses hydriques des materiaux poreux, permettant d'extraire des informations quantitatives a partir des donnees experimentales. Typiquement, des humidites inferieures a quelques
ISSN:1359-5997
1871-6873
DOI:10.1007/BF02480418