Compaction temperatures of conventional asphalt mixtures
Guidelines for determining mixing and compaction temperatures of conventional asphalt mixtures were published by the Asphalt Institute in 1962. Since the adoption of the performance grading (PG) system in North America, the use of modified asphalts has been growing continuously. It is well recognized that those 1962 guidelines recommend excessively high construction temperatures that can result in damage to modified asphalts. But why doesn’t the current system work? Is kinematic viscosity the wrong physical parameter? Are target viscosities too low? Or are the test parameters of 135°C and 6.8 s–1 inappropriate? Many attempts have been made to develop more rational guidelines, but none have been universally adopted at this time.