edge and the new hot mix where the hot and cold edges had not melted together well. That was data we had never been able to see before, so it was pretty exciting.” No potholes left behind The ADOT&PF wants to move in the direction of continuous, full-cov- erage asphalt pavement density testing for future projects, especially major arterials, highways, and main thoroughfares. They recently received a State Transportation Innovation Council (STIC) incentive award from the FHWA, and they want to use the funds to implement this technology more fully. “We want to use PaveScan RDM on a project in the near future for actual acceptance of the compaction of the highway,” Giessel said. “Instead of the drilled cores that we are currently using, we would use the drilled cores only to calibrate the machine at the beginning of the project. Then we would accept the density on the rest of the project based on the GPR readings. That would be a huge step forward for us.” ADOT&PF is looking forward to moving away from using statisti- cal methods to generate a distribution of values because, even if the average value is good, there could still be weak areas that are below paving standards. These are more likely to cause early failures and maintenance costs, as well as additional costs due to the need for re- paving earlier than planned. With their new technology, they can locate specific weak areas that are below established standards. For the upcoming STIC project, ADOT&PF proposes paying the con-
tractor based on the average compaction value, with a bonus (up to 5 percent) if the contractor gets the average up to 96 percent. However, if compaction is below 92 percent, the contractor will have to remediate it by going back and applying a sand seal with an appropriate sealer/ binder on all low mat sections and joints. Giessel anticipates that this carrot and stick approach will encourage contractors to pay more attention to quality control up front, so they do not have to go back and perform any required remediation. “We hope their game will be dialed up a bit when they have to go back and fix areas they missed if they do not compact well,” he said. “It will raise everybody’s awareness of quality work. Basically, we will have no potholes left behind with this program.” As the first state proposing to use the new system for acceptance, Alaska has received encouraging support from the FHWA, which likes the idea of fixing things that are not right before the contractor leaves the project. They also support the idea of not having to fund another project prematurely because something was not done well. It is just good economic sense to do everything right the first time. This technol- ogy and implementing this type of specification has the potential to save the state millions of dollars in annual maintenance. ROB SOMMERFELDT is transportation application specialist with Geophysical Survey Systems, Inc. (www.geophysical.com). A skilled trainer responsible for educating customers on a wide variety of GPR applications and products, he has more than 30 years of experience in software development, network administration, and technology education.
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