Temperature Variation through Deep Multigrade Asphalt Pavements and Proposed Method for Accounting for Fluctuations

Multigrade bitumen asphalt is a quality asphalt product that is not used in many places globally. Multigrade bitumen is believed to be less sensitive to temperature, which gives it an advantage over conventional binders. Previous testing has shown that asphalt temperature changes greatly with depth, but currently the industry standard is to nominate a single temperature for design. For detailed design of asphalt roads, perhaps asphalt layers should be divided into nominal layer depths and different modulus and fatigue equations/values should be used to reflect the temperatures of each respective layer. Previous laboratory testing conducted on multigrade bitumen asphalt beams under a range of temperatures and loading conditions was analyzed. The samples tested included 0% or 15% recycled asphalt pavement (RAP) to determine the impact of the recycled material on the fatigue life and stiffness of the pavement. This study investigated the temperature susceptibility of multigrade bitumen asphalt pavements compared with that of conventional binders by combining previous testing that included conducting a range of fatigue tests, developing complex modulus master curves for each mix, and a study of how pavement temperature changes through pavement depth. The materials properties were analyzed using the pavement design software. This investigation found that the final design of the pavement is greatly affected by the nominated pavement temperature and respective material properties. This paper outlines a potential revision to the current design approach for asphalt pavements and proposes that further investigation is needed into pavement temperature and its incorporation into design.