Nonlinear thermal expansion and contraction of asphalt concrete

Asphalt concrete for paving roads is a viscoelastic material. In the prediction of thermal stress in asphalt pavements, the thermal expansion-contraction property of the material is required. In current practice, thermal expansion-contraction is assumed to be a linear function of temperature, and a constant thermal coefficient is used. The fact that a viscoelastic material may have a glass transition temperature and the thermal property may have a discontinuity at the glass transition temperature has not been considered. This study investigates the thermal nonlinearity of asphalt concrete. In this research, the thermal expansion-contraction was continuously measured on a single type of asphalt concrete in the temperature range from +40°C to -40°C. It was found that the thermal expansion-contraction was a continuous nonlinear function of temperature, resulting in a variable thermal coefficient. Evaluations of the effect of the nonlinearity indicated that the assumption of thermal linearity can result in moderate errors in stress prediction in asphalt pavements.Key words: asphalt concrete, thermal expansion-contraction, thermal coefficient, nonlinear thermal behaviour, asphalt pavement, thermal stress.