Seasonal effects on a low-volume road flexible pavement

Abstract

Alaska’s Parks Highway is a 323-mi, asphalt-paved, predominantly two-lane, low-volume roadway that links the state’s two largest cities (Anchorage and Fairbanks). The effects of thawing on this low-volume roadway pavement were assessed, and seasonal adjustment factors for the different pavement layers were developed. Falling weight deflectometer (FWD) testing was carried out weekly during springtime at three temperature data probe sites. The purpose of the FWD tests was to monitor the pavement structural conditions and moduli variations during the spring thaw and recovery periods. When the pavement began to thaw, how quickly thawing progressed, and whether the pavement returned to an equilibrium summertime state were also determined. Observations indicated that profound changes in backcalculated modulus values could occur within 1 week of thaw onset. In addition, moduli were used to develop modular ratios for the subgrade and base course layers. Results showed that while thawing, the subgrade and base course layers reached about 30% to 40% and 50% to 70%, respectively, of their summertime reference moduli. These ratios were lower than those currently used in Alaskan pavement design. Additional testing should be conducted to verify the proposed seasonal adjustment factors. Surface moduli values, calculated and plotted without the need for the pavement layer thicknesses, are useful in instantly identifying whether partial thawing has occurred.