ForConstructionPros.com

The first phase of the project involved dealing with the existing runway surface. The specification for the new runway base called for the old runway to be reclaimed with a concrete and emulsion stabilizer. The reclaimed runway and the concrete and emulsion stabilizer prevented the need for any additional base material and thicker lifts of hot mix asphalt on the wear surface.

Because of the unique nature of the base construction, Northstar Materials chose not to do the work and had to subcontract that portion of the project. "I had never seen anything like this before and to my knowledge, it's the first time it had ever been done in Minnesota," says Jeremy Ganske, asphalt and aggregate operation manager for Northstar Materials.

Old runway reclaimed
The existing runway was reclaimed 10 inches deep. Then, Portland cement was spread over the reclaimed runway. The runway was reclaimed a second time, during which asphalt was injected into the material. "It is almost like concrete when finished, because it is a hard and smooth surface," says Ganske.

With the base material ready, laying asphalt began. The job specification called for P-401, a Superpave used at airports. P-401 is a high level of Superpave that comes with its own set of Federal Aviation Administration specifications.

"What distinguishes P-401 from other Superpave asphalts is the percent within limits (PWL) specifications," says Ganske. "What this means is that contractors are not only required to meet requirements, but to stay consistent within certain limits." The consistency is set during paving of a test strip. Once the consistency is set, any deviation results in a penalty.