Assessment of Flexible Pavement Response During Freezing and Thawing from Indoor Heavy Vehicle Simulator Testing

During the spring thaw period, pavements experience a significant decrease of their bearing capacity, which leads to increased deterioration during that season. The Ministry of Transportation of Quebec enforces load restrictions during the thawing and the recovery of the pavement structures to ensure they are protected from excessive thaw associated damages. The main objective of this paper is to present the results of an investigation of the structural behaviour of pavement structures during freezing and thawing under laboratory controlled conditions using the Laval University Heavy Vehicle Simulator (HVS). The results of the study will be used to develop criteria to assist the authority in the decision making process for the implementation and the removal of load restrictions. A typical four-layer flexible pavement structure was built inside an indoor concrete test pit at Laval University. The pavement section was instrumented to monitor horizontal strains in the asphalt concrete layer as well as vertical stress, vertical strain, and water content in each unbound layer and in the subgrade soil. Temperature was also monitored in all layers. The new HVS was used to impose 5000 kg (normal conditions), 5500 kg (winter premiums) and 4000 kg (spring load restrictions) loads on a standard dual-tire assembly. The load simulator was also used to induce freezing up to a depth of 1.5 m in the pavement structure and to induce thawing. The results obtained showed that during the thawing, the maximum strains occurred when the thaw front reached a depth of 0.9 m. Finally, it was found that the spring load reduction policies used in Quebec Province reduce the weighted annual damage by approximately 13 % during thawing, the strains and stresses decreased rapidly when the frost front reached subbase. Pavement damage caused by the standard load in these conditions can be considered negligible.