Hello, I’m John D’Angelo of D’Angelo Consulting. Formally I worked for the US Department of Transportation Federal Highway Administration in the office of Pavement Technology. With this video we will discuss the Superpave asphalt binder specification and how it relates to pavement performance based on traffic, climate and aging. We will explore how the asphalt binder is selected based on the climate where the pavement will be placed, the traffic it is expected to carry and the types of pavement distress it may experience… An asphalt pavement is expected to perform under extreme climate conditions from the heat of summer to the frozen winter. It also has to carry varied traffic from small sports cars to heavily loaded trucks. Proper selection of the asphalt binder to address these varying conditions is critical to good performance and the Superpave Asphalt Binder Specification was specifically developed to do just that. Asphalt binders are designated for PG (Performance Grade) and then the temperature ranges for which will be used, as an example PG 64-22. The 64 is the expected high pavement temperature and the -22 is the expected low pavement temperature that the binder will experience based on the climate where the pavement will be built. Asphalt binder properties change with temperature. At high temperatures, it is a viscous fluid and at low temperatures, it acts as an elastic solid. As mentioned by Jean-Pascal Planche in a recent video, bitumen is a viscoelastic material exhibiting different behaviours at different temperatures. This variation in properties is taken into consideration in the Superpave Specification. As the asphalt binder ages in the pavement, its properties also change and this affects its performance. As the asphalt binder ages, it becomes stiffer and more brittle making it more prone to cracking. The Superpave specification addresses this by testing at various aging conditions and temperatures to evaluate how the binder will perform as it ages. Rutting of the pavement typically happens early in its life and at high temperature. Cracking from traffic loading or fatigue cracking happens later in life and at moderate temperature. Low temperature cracking also occurs later in the pavement's life caused by exposure to very low temperature. Under the Superpave specification, three aging conditions are tested. The unaged binder, early life simulated in the Rolling Thin Film Oven (RTFO), and long life simulated in the Pressure Aging Vessel (PAV). This allows for an evaluation of how the binder will perform throughout its life in the pavement. To evaluate the early life conditions, testing is done at very high temperatures on unaged binder to determine if it will be workable during construction. The binder is then tested at high pavement service temperature on RTFOT short-term aged binder to determine the potential for rutting. To evaluate the binder's later life conditions, testing is done on PAV long-term aged binder at moderate temperature to determine cracking associated with traffic loading and at very low temperatures to evaluate low temperature cracking. Traffic is taken into consideration by adjusting the binder grade. If slow speed or heavier traffic is expected, the binder grade is adjusted so a stiffer binder is used. All these items are combined to create a complete specification set. To summarize: the binder is selected based on the climate where the pavement will be placed both high temperature and low temperature being taken into account. Testing is done to address specific types of pavement distress such as rutting, load-related cracking and low temperature cracking. Traffic is considered by adjusting the grade selection to stiffer materials for slow moving or heavier traffic. Thanks for your attention and enjoy the rest of the MOOC…