Mechanistic-based comparisons for freeze-thaw performance of stabilized unpaved roads

Unpaved roads in seasonally frozen regions are frequently subjected to frost boils and other freeze-thaw related damage. In this study, a range of several promising stabilization technologies selected based on a comprehensive literature review were evaluated for their ability to improve the freeze-thaw performance of unpaved roads under the same set of geological, climate, and traffic conditions. A total of 17 test sections were constructed using nine geomaterials, three chemical stabilizers, and three types of geosynthetics over a 3.2 km stretch of unpaved road. Visual inspections and extensive dynamic cone penetrometer (DCP) and falling weight deflectometer (FWD) tests were conducted over two seasonal freeze-thaw periods to compare the surface performance and mechanical properties of the various test sections. A weather station and subgrade temperature sensors were installed to monitor the depth and duration of soil freezing, and to determine the critical thaw-weakening periods during which to conduct field tests. The test results revealed that sections with macadam stone base (MSB) layers yielded the best freeze-thaw performance in terms of elastic modulus among all the stabilization methods examined. Multiple regression analyses of measurements taken after thawing showed that the aggregate layer modulus had a statistically greater influence on the overall composite modulus of the MSB sections, but the modulus of the underlying weaker subgrade layer had a greater influence in the sections without MSB layers. The field test results also demonstrated that the stiffness and strength of underlying subgrade layer in the MSB sections were improved due to the benefits offered by the MSB layers.