Two stretches of Wisconsin's STH 133 in Grant County now provide a safer and much improved travel surface for motorists using the road between Muscoda and Boscobel thanks to the quality warranty pavement work executed by Mathy Construction this past summer.
Mathy served as the general contractor on the $7.5-million project, which required full removal of the old asphalt surface, grading and reconstructing a new aggregate subbase, and the placement of a new Type E-1 hot-mix asphalt overlay.
Wisconsin Department of Transportation awarded Mathy the warranty contract, which required the contractor to install orange safety fence and temporary "Native Prairie" signs along portions of the project to prohibit work activity within an adjacent Department of Natural Resources' designated protected prairie environment. Any topsoil salvaged from areas along the designated prairie environment had to be stockpiled separately from other topsoil, so that it could be returned to the prairie areas during final grading of the adjacent right-of-way.
Although stipulations of the warranty contract required Mathy to stand behind its work for five years after completion of the final surface lift, it also proved beneficial to both WisDOT and the contractor. The contract eliminated the usual jobsite testing (core sampling, documented temperature readings, density compaction testing, etc.) as well as much of the mix production testing required by WisDOT, and it also allowed Mathy the flexibility to design the project's mix. The only stipulation WisDOT imposed on mix design was that it conformed to its Type E-1 specification (which is considered a Superpave design). The 2.5-inch base course mix design consisted of 45-percent 19mm limestone aggregate, 15-percent manmade sand, 20-percent natural sand and 20-percent reclaimed asphalt pavement (RAP). The 2-inch surface course mix design consisted of 12.5mm limestone aggregate with the same quantities of materials used in the base course design, with the exception of RAP (only 10-percent RAP content was used in the surface course). Both mix designs contained 4.8-percent of performance grade (PG 58-28 for base course mix and PG 64-22 for surface course mix) liquid asphalt cement binder, with some adjustment made based on the binder content of the RAP additive.
Prior to construction, Mathy provided WisDOT's project engineer with a quality control plan outlining the contractor's material and construction control processes. The plan included a list of the quality control tests to be used in controlling the material and construction quality. It also included sampling, testing and documentation frequencies, as well as the HMA pavement job mix formulas (JMF) planned for the project and the method used to develop the JMF. At the completion of the project, Mathy is required to provide documentation of the project to the state's engineer.
The contract required Mathy's Quality Control/Quality Assurance lab testing procedures to pull a sample from the mix produced every 1,000 tons. Mathy pulled a sample every 800 tons produced and conducted tests (in its portable lab at the production facility) to monitor gradation, absorption and compaction characteristics of the mix sent out to the project.
"We only conducted verification testing approximately one in 10 samples the contractor tested," notes Scott Lowry, WisDOT project manager.
All documentation required at completion of the project will include all quality control test results and any changes made to the project's typical widths and depths of subgrade, subbase, base and surface. That documentation will be used when evaluating the pavement's performance over the five-year warranty period.