ABSTRACT
Abstract Appropriate testing of freeze thaw resistance requires a sufficient understanding of the macroscopic and microscopic mechanisms leading to frost damage under freeze thaw and deicing salt attack. Macroscopic and microscopic effects such as abnormal freezing of the structured and pre-structured gel water, depression of freezing point by dissolved salts and by surface interaction, supercooling and nucleation, transport mechanisms due to temperature gradients, and different thermal expansion of water and solid and the formation of micro-ice lenses connected with gel shrinkage is described. Macroscopic and microscopic for damage are described. On this basis the essential consequences for freeze thaw testing are outlined. The test procedures treated in RILEM TC 117 FDC freeze Thaw and Deicing Salt Resistance" are shortly discussed. The essential aim of any testing, the precision was meanwhile assessed for CDF test which is therefore recommended by RILEM. Future work especially with respect to internal damage is proposed. Keywords: Test Procedures, Freeze thaw resistance, internal damage, basic models
1 Introduction
Testing the freeze thaw resistance of concrete is no simple task. Since two contradictions have to be solved. Firstly, the long term behaviour should be measured within a time as short as possible. Secondly, the broad variety in modifications of frost attack shall be covered by a test procedure which must, on the other hand, be restrictive in the relevant test parameters to achieve a sufficient precision. Nevertheless, practical experience not at least of RILEM TC 117 FDC freeze Thaw and Deicing Resistance of Concrete" shows that a fair compromise is possible. To reach this aim some at least
semi-quantitative knowledge is necessary about the mechanisms generating the frost damage. A short survey of these mechanisms will therefore be given first in this contribution.
