Date of this Version
Nebraska Transportation Center Report #: SPR-PI (08) P309
This research was conducted to study more realistic explanations of how variables are created and dealt with during hot mix asphalt (HMA) paving construction. Several paving projects across the state of Nebraska have been visited where sensory devices were used to test how the selected variables contribute to temperature differentials including density, moisture content within the asphalt, material surface temperature, internal temperature, wind speed, haul time, and equipment type. Areas of high temperature differentials are identified using an infrared camera whose usefulness was initially confirmed with a penetrating thermometer. A non-nuclear density device was also used to record how the lower temperature asphalt density compared to the more consistent hot area. After all variables were recorded, the locations were marked digitally via a handheld global positioning system (GPS) to aid in locating points of interest for future site revisits in order to verify research findings. In addition to the location-based database system using Google Earth, an extensive database query system was built which contains all data collected and analyzed during the period of this study. Research findings indicate that previously assumed variables thought to contribute to decreased density due to temperature differentials, like haul time and air temperature, have little impact on overall pavement quality. Additionally, the relationship between groups of temperature differentials and premature distresses one year after paving was clearly linked.