HANOVER, N.H. (Nov. 28, 2017)--Fort McCoy, Wisconsin, is the site of an insulated pavements test that, if successful, will provide a cost effective, manageable solution for maintaining 270 miles of heavily-trafficked, cold weather impacted streets, parking lots and staging areas. The work is being conducted by a team from the Cold Regions Research and Engineering Laboratory, working in conjunction with the Fort McCoy Directorate of Public Works.
Leading the work is CRREL’s Engineering Resources Branch team. Part of their work was to install a prototype pavement section as part of the Army’s Installation Technology Transition Program. The approach uses an insulated pavement consisting of innovations in materials and cost-effective construction practices to withstand damage over time from repeated frost action.
Fort McCoy is located on 60,000 acres and is primarily used as a “Total Force” military training center hosting all branches of the service. In fiscal year 2017, more than 156,000 personnel were trained there, along with support for retirees and family members. The installation supports an abundant mobile population and heavy military and commercial vehicle traffic in a geographic area with average winter temperatures dipping well below freezing.
The installation’s DPW has experienced a number of asphalt roadways and other paved areas with shortened lifespans requiring costly annual repairs because of seasonal frost heaving and thaw settlement failure modes leading to distress of asphalt pavements, such as fatigue cracking, upheaval and potholes.
“We installed both moisture sensors and temperature probes within the test section that will allow us to see how the temperature gradient changes with the foam board insulation in place under the pavement,” said CRREL’s Alex Stott, a research mechanical engineer. “Between the four-inch pavement layer and two-inch thick insulation, we placed a subgrade consisting of 24 inches of small, loose stone aggregate. The subgrade soil’s thickness and placement will help keep the paved area dry and less apt to freeze.”
Capitalizing on previous CRREL pavement prototypes and modified construction procedures, the CRREL team designed and installed a prototype pavement section that uses low cost construction materials to provide insulation below the base course. This approach prevents sub-freezing temperatures from reaching the subgrade causing winter heaving from McCoy’s frost-susceptible, moisture-prone soils.
“The foam board insulation is a very light material and we do not need a lot of it, what we do need can easily be trucked in,” said Stott.
“We have a lot of heavy military and commercial traffic in support of Fort McCoy’s unique training mission,” said Mark Nelson, an engineering technician with Fort McCoy’s Construction Inspection Branch. “The test section is in an ideal location, with a sloped road, high water table, static and dynamic loads and it is in the ‘teeth’ of the northwest wind. We are very interested in seeing the test data.”
According to a cost analysis study conducted by project lead Marina Reilly-Collette, if this prototype test section is successful and the practice is extended to its inventory of other ailing pavements, Fort McCoy could potentially save up to 40 percent in construction costs through extensions in the lifespan of highway surfaces eliminating the replacement of the subgrade of base roadways. CRREL’s insulated pavements methodology costs less than 13 percent per additional mile than uninsulated pavement, making the up-front cost manageable and guarantees substantial long-term savings.
“The current prototype tests a new method of implementing the transitional section between the existing roadway and the insulated pavements repair section, avoiding differential freezing and potentially reducing installation costs, while improving safety,” said Reilly-Collette.
CRREL will continue to monitor the efficacy of this pavement solution over the next two years using a combination of instrumentation for real-time monitoring and periodic non-destructive testing.
CRREL is one of seven laboratories of the U.S. Army Engineer Research and Development Center, headquartered in Vicksburg, Mississippi.