Pacific Builder and Engineer, August 2012
Volume 118, Number 8
By Paul Fournier
The Oregon Department of Transportation (ODOT) recently had a section of Interstate 5 paved with advanced hot mix asphalt as part of a nationwide demonstration program involving thin pavement overlay incorporating highly polymer-modified asphalt binder (HiMA).
Knife River Materials manufactured and installed the new HiMA mix for ODOT’s demonstration on a two-mile segment of northbound lanes of I-5 near Medford, the seat of Jackson County located in southern Oregon near the California border.
Production of the HiMA thin-lift overlay is based on specifications developed by the Northeast Pavement Preservation Partnership (NEPPP), a regional DOT group dedicated to advancing pavement preservation. Titled “Superpave 9.5mm Highly Polymer-Modified Thin Overlay Specifications (PMTOL),” the new regional specifications were designed by NEPPP as a pavement preservation strategy to extend a pavement’s service life. The new mix is intended to be placed on pavements that are structurally sound.
As a member of the Rocky Mountain West Pavement Preservation Partnership (RMWPPP), a sister regional partnership, ODOT learned about the program and decided to conduct a demonstration similar to those undertaken by state transportation agencies in New Hampshire, Vermont, and Minnesota.
The test of HiMA thin overlay would serve as an adjunct to ODOT’s continuing search for economical preservation methods that will boost pavement service life on high-volume roads. In addition to environmental and load-related factors, these roads experience rutting due to studded tire-abrasion and raveling where open-graded surfaces were used. Five years ago, ODOT began using hot-applied chip seals on moderate- to high-volume-traffic roads with pavements nearing the end of their service life. The goal of using hot-applied chip seal is to provide additional service life to such highways that cannot be paved due to current budget constraints. Several of the hot chip seals are still in place after five years and ODOT anticipates realizing a service life of eight years from them. Ideally, officials are looking for a preservation process that would lengthen pavement service life by up to 15 years.