Application of Tensile Creep Test and Viscoelastic Method to the Analysis of Thermal Stresses at Low Temperatures

The paper presents the viscoelastic method of thermal stresses calculation with utilization of results from tensile creep test (TCT) at a temperature range from −20 to +20 °C (in the case of asphalt concrete with styrene-butadiene-styrene (SBS) polymer-modified bitumen from −30 to +20 °C). Two types of neat road bitumen 35/50 and 50/70 and polymer SBS-modified bitumen 45/80–55 were tested for tensile creep properties at low temperatures. On the basis of laboratory results, the master curves of stiffness modulus were developed using Richards model. For calculation of thermal stresses, Burgers’ rheological model was used, and rheological parameters describing elastic and viscous properties of the asphalt mixtures were determined. Then the viscoelastic method was applied based on the assumption that asphalt layer is made of a linear viscoelastic material that responses under load at a constant temperature and can be mathematically described by the Burgers model. It was concluded that the laboratory TCT test provides reliable results for thermal stress calculations, and that the viscoelastic method of thermal stresses calculation allow to model different rates of temperature and provides good foundation for the calculation of the thermal stresses generated by the real winter thermal cycles.