Experimental Damage Assessment of Flexible Pavements during Freeze-Up

Abstract

Frost action is one of the most important factors contributing to pavement damage in cold regions. Frost action causes a gain regarding the bearing capacity of flexible pavements due to the viscoelastic response of asphalt concrete and to the freezing of pore water in granular materials and soils. Pavement strengthening with frost penetration has led some transportation agencies to allow winter weight premiums for the trucking industry, but rational and technical decision criterion for the increase of the axle load limit are limited. The objective of this project was thus to document the mechanical behavior of flexible pavements as a function of frost penetration and axle load. The Laval University full-scale heavy-vehicle simulator was used to monitor the response of two flexible pavements built in a 24-m3 indoor laboratory pit over a silty sand and low-plasticity clay subgrade soils, respectively. The pavements were instrumented to monitor temperature profiles, surface deflection, stress, strain, and moisture in each layer. The simulator was used to freeze the pavement downward using a −10°C surface temperature, and to periodically load the pavement surface using a standard dual-wheel set (half-axle) loaded in the range of 4,500–6,250 kg. The results collected allowed documenting response modification of different pavement structures changes as a function of frost penetration and temperature. It was also shown that the pavement response variation with respect to axle load variation becomes nonsignificant when 600-mm frost depth is reached, and that the associated pavement damage becomes negligible when frost depth reaches 400–500 mm.