Abstract
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 language | English |
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| Title of host publication | Frost resistance of building materials |
| Place of Publication | Lund, Sweden |
| Publisher | Lund Institute of Technology, Div. of Building Materials |
| Publication date | 1996 |
| Pages | 127-140 |
| Publication status | Published - 1996 |
| Event | Frost Resistance of Building Materials, Nordic Research
Seminar - Lund, Sweden Duration: 1 Jan 1996 → … |
Conference
| Conference | Frost Resistance of Building Materials, Nordic Research Seminar |
|---|---|
| City | Lund, Sweden |
| Period | 01/01/1996 → … |