Now in its third year, the hot in-place preservation approach Waukesha County (WI) Public Works' Highway Operations Division has initiated as a cost-effective solution for maintaining and extending the service life of its rural road network continues to play a vital role in maximizing taxpayer dollars.
Rick Harley, senior engineering technician for the department, says the program has been growing ever since the county first treated 100,000 to 120,000 square yards of road surface three years ago. In 2007, Harley expects to treat over 180,000 square yards of road surface with the hot in-place process.
"We really increased the hot in-place process this year because we inherited some roads that don't carry a lot of heavy truck traffic, and this approach provided the best solution to improving and preserving those roads," Harley notes. "Typically, hot in-place candidates are roads that need some type of treatment to retard some of the surface reflective cracking that allows moisture to seep into the base structure and will eventually cause the road to deteriorate much faster if untreated. The hot in-place process rejuvenates the surface course before we place a new overlay on the road, and that gives us another six years of service life out of that road before we have to consider additional treatments or whether it's time to reconstruct the road. It's not going to stop reflective cracking from coming up through the new overlay, but we believe it's a cost-effective treatment for roads that are not exposed to heavy truck traffic."
Hot in-place solution
One road the department addressed this summer is a portion of County Hwy P south of Mapleton. The road was last reconstructed in 1975 as a 5- to 5.5-inch full-depth asphalt structure. It's a rural road that does see its fair share of commuter traffic, farm traffic and some truck traffic, but traffic counts conducted by the county determined it to be an ideal candidate for hot in-place recycling.
Gallagher Asphalt's Hot In-Place Division out of Thorton, IL was contracted to recycle approximately 50,000 square yards of this particular two and half-mile stretch of road, rejuvenating the surface mat to a depth of 1.5 inches. Following the hot in-place process, asphalt contractor Payne & Dolan out of Waukesha placed a new 1 3/4 inch virgin hot mix Superpave overlay on the rejuvenated hot in-place mat.
"This road had some reflective cracking and other surface deformations, and the hot in-place process takes care of those surface flaws and also re-profiles (corrects the drainage crown) the road and removes any rutting or other low spots before the new surface course is put down," Harley says. "We expect to see some reflective cracking start to show up in about three years from now, but this particular preservation approach allows us time to schedule a full reconstruction at a later date. There's been a considerable amount of growth along this road (residential development and retail development further south of the road project) and we know at some point we'll probably have to rebuild this road to handle increased traffic counts. But for now, we have a safe and good riding road in place."
Harley says the county's highway maintenance department uses a variety of solutions to maintain the quality of its road network. Mill and fill as well as foam injection are also used when they are determined to be the best approach, but hot in-place accounts for approximately 50 percent of the maintenance budget work performed on the roads.
"We look at a road's function and take into consideration the traffic volume of that road when deciding the best possible solution to use," Harley says. "It's not simply a matter of cost savings when deciding what approach to use. Hot in-place just happens to be one solution that's proving to perform well for us and much of our current maintenance budget is earmarked for projects involving hot in-place, which we expect to continue being one of our primary maintenance solutions."