Effect of seasonal frost conditions on the permanent strain behaviour of compacted unbound granular materials used as base course

Abstract

Frost action affects permanent strain behaviour of unbound granular materials' performance by causing an increase in saturation degree as well as a decrease in density. This research aims to improve the understanding on how the base granular materials' permanent strain behaviour changes through seasons. In order to characterise this behaviour, eight permanent strain tests were performed at various water contents, densities and test conditions. Freeze and thaw cycles, for drained and undrained testing conditions, were applied to samples to measure the contribution of frost action to the plastic deformation mechanisms. From the obtained results, it is concluded that the effect of the freeze–thaw cycle on the permanent strain behaviour of unbound granular materials used as pavement base is mostly explained by the increase of water content and, to a lesser extent, by the decrease of dry density.