During resurfacing of Highway 29 near Alexandria, Minnesota, the road surface was repaved over a distance of about 30 miles. The company that performed the work, Central Specialities Inc., used the PAVE-IR Scan quality control system for the first time. With this system, the temperature is recorded during asphalt paving, allowing conclusions to be drawn about the quality of the asphalt.
For road building companies, a high-quality result translates directly into money if there are financial penalties for not meeting contractually defined, quality criteria. Likewise, companies are rewarded if the criteria are met, the work completed ahead of schedule or the minimum requirements exceeded. It is therefore important for companies to be able to provide proof of their work and to be able to verify the quality.
One possibility for recording the quality during paving is the PAVE-IR Scan temperature control system. In this construction project, the scanner was employed for the first time in one of the projects used by the Minnesota Department of Transportation for collecting and evaluating temperature data during asphalt paving. The scanner was mounted on the back of the paver, measuring the temperature over the entire paving width.
Central Specialities Inc. reported that “The scanner considerably simplifies the recording of temperatures. It is compact and mounted outside of the work area. Moreover, the system is very easy to mount and quite compact. The scanner is, thus, a big step in the right direction.”
The surface temperature is constantly recorded during asphalt paving and displayed as a temperature profile on the paver’s display panel. The profile clearly shows where temperature differentials exceed specifications for the project. The real time display of thermal image and differential calculations allows the contractor to determine if process changes have had a positive effect on variability.
All information is stored locally and, via wireless communication, on a server. It can be viewed with the Pave Project Manager software package and used as proof of quality. This is because it has been shown that paving temperature has a large influence on the quality and service life of the road. Large fluctuations in the temperature of the asphalt mat can indicate material segregation or have an adverse effect on compaction uniformity and material density, all of which can lead to premature road failure.
This has been verified in studies undertaken by the Texas Transportation Institute, which were performed using the predecessor model, PAVE-IR, with a sensor beam behind the screed. In Minnesota, temperature data has been collected and evaluated by the Department of Transportation for four years. In 2014, 20 projects have specified the use of thermal data collection systems, all of which will be using either the PAVE-IR Scanner or Beam.
Paul Angerhofer, MOBA field support technician, says: “We know that the service life of a road increases if segregation is kept to a minimum. And segregation occurs if there are high temperature differences during asphalt paving. This, in turn, means that maintenance and resurfacing costs drop dramatically if the asphalt was paved at the correct, uniform temperature. Signs of wear then do not occur until later and the road needs to be repaved less frequently.”
