Rehabilitating Asphalt Highways

Lastly, the existing outreach and technology transfer efforts of the Coal Combustion Products (CCP) Extension Program at OSU will be focused on county, state, and federal transportation officials and other end users of the technology.

This project will demonstrate that when non-concrete quality fly ash in combination with lime or lime kiln dust are properly incorporated into FDR reconstruction of a flexible pavement, the use of fly ash can be economically attractive while offering increased structural and service performance, and should not lead to a degradation of environmental quality.

"One of our objectives in this research is to demonstrate the many potential environmental benefits associated with the use of fly ash in the FDR of asphalt pavements," says Associate Professor Harold Walker of OSU's Department of Civil and Environmental Engineering and Geodetic Science.

Delaware County pavement
Delaware County (just north of Columbus) is the fastest growing county in Ohio. In collaboration with the Delaware County Engineer's Office, Section Line Road between State Route 42 and Home Road was selected for FDR reconstruction in 2006.

The section of the road selected for study in this county measured 4.1 miles in length, 20 feet in width with minimal shoulders, and had a ¼-inch cross-slope consisting of an asphalt surface with thickness ranging from 5.25 to 14 inches (average of 10.28 inches). The original pavement was underlain by a base course ranging from one to 11 inches (average of 5.18 inches) thick.

The pavement sampling and design was to be carried out by EDP Consultants under the supervision of OSU. A total of nine sections were constructed using the following six mixes:

• 4-percent lime with 6-percent fly ash, 8-inch stabilization depth (0.7 mile)
• 5-percent lime kiln dust with 5-percent fly ash, 8-inch stabilization depth (0.6 mile)
• 3-percent lime kiln dust with 1.4 gallons per square yard emulsion, 8-inch stabilization depth (0.7 mile)
• 5-percent cement, 12-inch stabilization depth (0.8 mile)
• 2-percent cement with 1.6 gallons per square yard emulsion, 8-inch stabilization depth (0.3 mile)
• 5-inch mill and fill (two 0.1-mile sections at the north and south ends of the project, and a 0.7-mile as well as 0.1-mile sections near the middle of the project).

The FDR rehabilitation of the section Line Road was completed in five phases. Beginning in August, Strawser Paving first milled and removed 5 inches of the existing pavement asphalt surface. In the second phase, Base Construction pre-pulverized the remaining pavement materials to various depths as listed above.

The third phase involved treating the pulverized pavement materials with admixtures as outlined above. Water was then added to the mix and it was compacted immediately. The last phase involved resurfacing the pavement with 5 inches of hot mix asphalt and was completed by mid-October.

"All construction has been completed and our office believes that the construction portion of the project has cost-efficiently improved the structural strength and has allowed for the existing roadway materials to be homogenously stabilized by integrating fly ash, lime, and lime kiln dust," says Jerry Ungashick, project manager, Delaware County Engineer's Office.

Warren County pavement
Warren County, just South of Cincinnati, is the second fastest growing county in the state. The Long Spurling Road (County Road 171) located in the southeastern part of the county in Harlan Township was chosen by the Warren County Engineer's Office for FDR construction between SR132 and the north driveway to the LM Animal Products Plant.

The failing pavement was 0.4 miles in length, 20 to 21 feet in width with minimal shoulders and had a 2-inch asphalt layer on top of 4 to 6 inches of chipsealed pavement.

The pavement sampling and design was carried out by EDP Consultants under the supervision of OSU. Two sections were constructed as follows:

• 4-percent lime with 6-percent fly ash, 12-inch stabilization depth (0.32 mile)
• 5-inch mill and fill (0.08 mile)

The FDR rehabilitation of the Long Spurling Road was completed in five phases. Beginning in July, Strawser Paving milled and removed 4 inches of the existing pavement asphalt surface.