Freezing Shrinkage in Compacted Clays

This paper presents the results of volume change measurements on laboratory-compacted samples of five Alberta clay soils which have been subjected to closed-system, unidirectional freezing. It was found that for Standard AASHO compaction effort, maximum shrinkage occurred at degrees of saturation between 60 and 70 per cent. The compacted degree of saturation required for 0 per cent total volume change ranged from 86 to 90 per cent. Maximum freezing shrinkage was found to increase with an increase in plasticity of the soil. Increasing the compactive effort from Standard to Modified AASHO caused a reduction in the maximum measured shrinkage in a highly plastic, lacustrine clay. A hypothesis, based on Powers' and Helmuth's theory of volume changes in cement pastes on freezing, is suggested as a simplified explanation of the observed behaviour. Field data are presented showing the effects of subgrade freezing on the changes in surface elevation of an asphalt-surfaced highway.