In the second phase, Base Construction pre-pulverized the remaining pavement materials to a depth of 12 inches. The third phase involved treating the pulverized pavement materials with lime at an application rate of 4 percent and allowing the material to mellow for a 24-hour period.
After the mellow period, 6-percent fly ash from Zimmer power plant of Duke Energy was blended into the mix to a depth of 12 inches. Water was added to the mix and it was compacted immediately. The last phase involved resurfacing the pavement with 4 inches of hot mix asphalt and was completed by mid-September.
"Our office is glad to be a partner with Ohio State University, the Ohio Coal Development Office and Base Construction (as well as many other private suppliers) in this FDR project using fly ash," says ," says Kurt E. Weber, P.E., P.S., chief deputy engineer, Warren County Engineer's Office. "Using FDR to repair Long Spurling Road was much more cost-effective than the alternative method of total full depth reconstruction. We're anxious to see the long term results of this project and how this method can be utilized in repairing county and township roads in the future."
Pavement instrumentation and monitoring
During construction, the Delaware and Warren pavement sections were instrumented with the following structural and environmental monitoring devices:
- Strain gauges at bottom of asphalt layer
- Pressure cells at bottom of stabilized base layer
- Pore pressure devices at bottom of stabilized base layer
- LVDTs for measuring vertical deflections of pavement
- Lysimeters installed within the stabilized base to monitor leachate quality.
Data collection from the above monitoring devices is being carried out on a quarterly basis.
Falling Weight Deflectometer (FWD) tests (to measure pavement load deflection behavior, resilient modulus of pavement layers and subgrade soil, and base structural layer coefficient) are being carried out by the Ohio Department of Transportation.
The FWD tests carried out on the pavement before and immediately after completion of rehabilitation show that FDR of the pavements with fly ash (and lime or lime kiln dust) increased the elastic modulus of the base layer. The fly ash sections exhibited elastic moduli of base layers similar to cement and cement plus emulsion sections.
FWD tests will continue to be carried out twice a year to determine the longer term elastic moduli of the various sections constructed in this project.
The project findings will enable the users of the technology to reap significant cost savings when compared with the common practice of removing old pavement and rebuilding the roadway.
In addition, the technology addresses a very important environmental issue, says Professor William Wolfe of OSU's Department of Civil and Environmental Engineering and Geodetic Science.
"Since the production of one ton of cement produces about one ton of carbon dioxide, which is then released into the atmosphere," he says, "the widespread replacement of cement with fly ash in roadway reconstruction will result in significant reductions in the generation of this greenhouse gas."
This three-year project at OSU, totaling over $2 million, is funded primarily by the Ohio Coal Development Office of the Ohio Air Quality Development Authority with additional support from the Delaware and Warren County Engineers Offices, Base Construction, Carmeuse NA, Headwater Resources, and others.
"Last year, two counties in Ohio used Ohio coal-generated fly ash in reclaiming failed asphalt pavements," says Mark Shanahan, executive director of the Ohio Air Quality Development Authority, which manages the Ohio Coal Development Office. "This resulted in more durable highway infrastructure and promoted the recycling of pavement materials and coal combustion byproducts, both of which would otherwise have been landfilled."
Greg Samios, project manager of EDP Consultants Inc. adds, "The unique opportunity of a comparative mix design study has enabled EDP Consultants to increase our knowledge and understanding of how different chemical additives may benefit the recycling industry."
About the author: Dr. Tarunjit S. Butalia, P.E., is a research scientist and coal combustion products coordinator for the Department of Civil and Environmental Engineering and Geodetic Science at Ohio State University.