Materials and Structures

, Volume 31, Issue 4, pp 218–224 | Cite as

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

  • H. Pleinert
  • H. Sadouki
  • F. H. Wittmann
Scientific Reports

Abstract

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/cm3 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.

Keywords

Moisture Transport Swiss Federal Institute Moisture Distribution Moisture Profile Neutron Radiography 

Résumé

Les mouvements d’eau au sein de la structure poreuse d’un ouvrage peuvent l’affecter sérieusement, notamment par une dégradation physique ou chimique. Aussi est-il nécessaire de bien comprendre les mécanismes de transfert d’humidité pour une meilleure maîtrise des problèmes liés à la durabilité des constructions en matériaux poreux. Les transferts d’humidité sont souvent décrits d’une façon phénoménologique, par des équations de type diffusion, mettant en jeu un ou plusieurs coefficients de transfert. Une méthode de détermination des coefficients de transfert hydrique d’un matériau consiste à les extraire de l’information contenue dans les distributions spatio-temporelles de teneur en eau mesurées. La radiographie à neutrons s’avère être une technique de mesure non-destructive de très grande sensibilité pour détecter la présence d’eau, avec notamment une haute résolution spatiale. Une nouvelle technique d’analyse de la transmission neutronique a été développée et optimisée pour l’étude d’analyses hydriques des matériaux poreux, permettant d’extraire des informations quantitatives à partir des données expérimentales. Typiquement, des humidités inférieures à quelques mg/cm3 peuvent être détectées avec une résolution spatiale de 1 mm. À titre d’exemple d’application, nous avons déterminé les distributions spatiales d’humidité, à différents temps de dessiccation, dans un échantillon de brique, puis nous avons déduit le coefficient de transfert hydrique du matériau.

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Copyright information

© RILEM 1998

Authors and Affiliations

  • H. Pleinert
    • 1
  • H. Sadouki
    • 2
  • F. H. Wittmann
    • 2
  1. 1.Paul Scherrer InstituteVilligenSwitzerland
  2. 2.Swiss Federal Institute of TechnologyZurichSwitzerland

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