ABSTRACT
Highly porous materials like aerated concrete with entrained air content more than 45 % is nevertheless damaged during freezing. This should be attributed to its pore structure and degree of saturation rather than its low strength. This paper develops the concept of the critical saturation to which a microstructural explanation will be given, and a mechanism of frost damage to highly porous materials is discussed through the results of the following three experiments. DSC measurement has shown that an adsorbed water film remains unfrozen in between solid surface and ice. The critical saturation has been determined and the pore space occupied by the moisture has been identified, while the observation of frozen samples having critical moisture content by cryo-SEM has confirmed the compatibility with these results. A formula linking critical saturation with pore structure has been derived.
