Environmental Effects on the Predicted Service Life of Flexible Pavements

Abstract

Mechanistic-empirical pavement design methods for flexible pavements are based on the assumption that pavement life is inversely related to the magnitude of the traffic-induced pavement strains. These strains vary with the stiffness of various pavement layers. The stiffness of the asphalt varies with temperature and the stiffness of the unbound base and subgrade materials varies with water content. Because these relationships are nonlinear, the additional pavement life consumed by wheel loads at higher-than-average temperatures or water contents is not offset by savings at lower-than-average temperatures or water contents. Furthermore, the temperature and moisture effects cannot be considered separately and superimposed, they must be considered together. In this paper, seasonal temperature and water content variations observed at instrumented pavement sites in Tennessee are idealized and the combined effects of these seasonal changes on predicted pavement life are evaluated for three typical pavement profiles. The results of the parametric study show that the temperature averaging period, the temperature gradient in the asphalt, and the timing and duration of wet base and subgrade conditions all affect the estimation of pavement life.