Fort McCoy News Dec. 8, 2017

Insulated pavement being tested at Fort McCoy

BY MARIE DARLING
U.S. Army Engineer Research and Development Center

Fort McCoy is the site of an insulated pavement test that, if successful, will provide a cost-effective, manageable solution for maintaining the installation's 270 miles of heavily-trafficked streets, parking lots, and staging areas during cold weather.

The work is being conducted by a team from the Cold Regions Research and Engineering Laboratory (CRREL) working in conjunction with the Fort McCoy Directorate of Public Works (DPW).

Leading the work is CRREL's Engineering Resources Branch team. The team installed a prototype pavement section as part of the Army's Installation Technology Transition Program. The approach uses an insulated pavement to withstand damage from frost.

U.S. Army Cold Regions Research and Engineering Laboratory Mechanical Engineer Alex Stott prepares a foam board insulation layer of experimental roadway Nov. 17 at Fort McCoy.
U.S. Army Cold Regions Research and Engineering Laboratory
Mechanical Engineer Alex Stott prepares a foam board insulation
layer of experimental roadway Nov. 17 at Fort McCoy.
Photo by
Marissa Torres

Fort McCoy is located on 60,000 acres has miles and miles of paved roadways. In fiscal year 2017, almost 156,000 personnel trained there using those roads. The installation supports heavy military and commercial vehicle, and average winter temperatures drop well below freezing.

A number of asphalt roadways and other paved areas require costly annual repairs because of seasonal frost heaving leading to problems like 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 Alex Stott, a research mechanical engineer with CRREL. "Between the 4-inch pavement layer and 2-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, which causes winter heaving due to Fort 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 DPW'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."


A convoy travels on Fort McCoy roads Nov. 3. Photo by Scott T. Sturkol

According to a cost-analysis study conducted by project lead Marina Reilly-Collette, if this prototype test section is successful and used throughout post, Fort McCoy could potentially save up to 40 percent in construction costs through extensions in the lifespan of highway surfaces. CRREL's insulated pavements methodology costs less than 13 more percent per mile than uninsulated pavement, making the up-front cost manageable and guaranteeing 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 pavement over the next two years using a combination of real-time monitoring and periodic nondestructive testing.

CRREL is one of seven laboratories of the U.S. Army Engineer Research and Development Center, headquartered in Vicksburg, Miss.