Modelling critical degrees of saturation of porous building materials subjected to freezing

Ernst Jan De Place Hansen

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearch


    Frost resistance of porous materials can be characterized by the critical degree of saturation, SCR, and the actual degree of saturation, SACT. An experimental determination of SCR is very laborious and therefore only seldom used when testing frost resistance. A theoretical model for prediction of SCR based on fracture mechanics and phase geometry of two-phase materials has been developed.The degradation is modelled as being caused by different eigenstrains of the pore phase and the solid phase when freezing, leading to stress concentrations and crack propagation. Simplifications are made to describe the development of stresses and the pore structure, because a mathematical description of the physical theories explaining the process of freezing of water in porous materials is lacking.Calculations are based on porosity, modulus of elasticity and tensile strength, and parameters characterizing the pore structure and its effect on strength, modulus of elasticity and volumetric expansion. Also the amount of freezable water and thermal expansion coefficients are involved. For the present, the model assumes non air-entrained homogeneous materials subjected to freeze-thaw without de-icing salts.The model has been tested on various concretes without air-entrainment and on brick tiles with different porosities. Results agree qualitatively with values of the critical degree of saturation determined by measuring resonance frequencies and length change of sealed specimens during freezing.The reliability and usefulness of the model are discussed, e.g. in relation to the description of the pore structure. Based on this analysis, some new adjustments of the model are indicated. When further knowledge of the values and the importance of the different parameters is obtained, several of the tests involved will be unnecessary, making the model more useful in practice.Keywords: Brick tile, concrete, critical degree of saturation, eigenstrain, fracture mechanics, frost resistance, pore size distribution, pore structure, stress development, theoretical model.
    Original languageEnglish
    Title of host publicationFrost resistance of building materials
    Place of PublicationLund, Sweden
    PublisherLund Institute of Technology, Div. of Building Materials
    Publication date1996
    Publication statusPublished - 1996
    EventFrost Resistance of Building Materials, Nordic Research Seminar - Lund, Sweden
    Duration: 1 Jan 1996 → …


    ConferenceFrost Resistance of Building Materials, Nordic Research Seminar
    CityLund, Sweden
    Period01/01/1996 → …

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