VERTICAL MOVEMENTS AND CRACK-WIDTH CHANGES ON HIGHWAY PAVEMENT SURFACES

Abstract

The results of periodic pavement elevation and crack-width measurements taken over a period of three to four years are presented. Both surface elevation and crack-width changes are shown to follow a similar seasonal cycle. Results show that the sub-grades studied were frozen as closed systems. It is shown that with closed system subgrade freezing the resulting vertical displacement of the pavement may be either positive or negative depending on the moisture content of the subgrade. The negative case, corresponding to vertical freezing shrinkage, occurred with dry clay subgrades. For a given observation section, seasonal surface movements in a vertical direction are shown to vary from the traffic lanes to the shoulders. The difference is explained in terms of corresponding differences in the subgrade moisture conditions.Results are presented which indicate that seasonal changes in the width of transverse pavement cracks cannot be fully explained in terms of simple thermal expansion and contraction in the asphaltic concrete pavement. Indirect evidence is presented which suggests that horizontal freezing shrinkage in a subgrade contributes to the seasonal cycle of crack-width changes.