The Badger State Still on the Superpave Bandwagon

While the actual number of "Superpave miles" in Wisconsin's roadway system is low-approximately 4 to 5 miles-it has made an impression that greatly exceeds its physical presence. Tom Brokaw, asphalt, aggregate and soils engineer at the Wisconsin DOT, says the department has been very happy with Superpave.

"On the test sections we have put down, the data shows that the Superpave sections had no rutting problems, displayed only 20% reflective cracking-versus 55% on our conventional pavements-and a lower distress index than conventional pavements," he explains, adding that the winter of '93­p;'94 was a very cold one for Wisconsin, so the sections put down in 1992 were put to the test.

"We don't see any problems," Brokaw says. "It looks to be a good package SHRP has put together-the problem is educating people as to what Superpave is. A lot of people see that it can only be a coarse mix, but we can even see that there are finer mixes that will meet the Superpave guidelines. There's a lot more flexibility in the guidelines than some people think."

While Brokaw say he does not see any drawbacks to the system, he does express uncertainty about the gyratory compactor used to design Superpave mixes. "The main difference between Superpave and conventional mixes is the method of compaction, and the gyratory compactor costs around $28,000. And the field use of the gyratory compactor is going to be a hang-up; we are not sure what the specs for field use are going to be. That is one of the reasons we are going a little slow on this."

Despite this reservation, the few miles of Superpave mix Wisconsin has put down have impressed the DOT so much that they hope to add some additional Superpave miles this year, most likely on a "change bid" system where the contractor requests the switch to this type of mix. In addition, Brokaw says the department is considering accepting bids with Superpave mixes for projects put out for bid this year.