Effects of Thermal Properties on Pavement Fatigue Life

Abstract

Asphalt pavement performance is highly temperature dependent due to the viscoelastic behavior of the binder. Although rheological characteristics of bitumen (e.g., softening point, elastic recovery) are widely analyzed, thermal properties as diffusivity (or its components conductivity and specific heat capacity) are rarely tested. The most up-to-date design processes use asphalt master-curves to calculate temperature-dependent stiffness for versatile weather conditions, yet the temperature susceptibility of the mixture is neglected. In this paper a full approach is presented in order to determine the sensitivity of the pavement to changing in thermal properties. Surface temperatures are based on real-life data, in-depth temperatures are calculated via 1-D Fourier's heat transfer equation with the primary governing variable of diffusivity. The stiffness of the mixture is predicted by the Witczak–Bari model for every centimeter of depth to get a full stiffness profile. Multi-layer elastic theory is used to calculate pavement response. To evaluate conditional numerical sensitivities within the selected parameter space, 200 different combinations of thermal conductivity and specific heat capacity were tested as theoretical inputs. The connection between fatigue life and these numerical parameters was found non-linear. It was discovered that an increase of 1 W/mK in thermal conductivity can cause an average fatigue life reduction of 7.2%, while a 100 J/kgK change in specific heat capacity increases fatigue life with 1.0%. The ultimate general sensitivity analysis to thermal diffusivity showed that in the typical range of this property relative fatigue life can vary between 88.5–104.0% of the base scenario.