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Innovative Process
Wins ARRA Award
Each year, since 1985, the Asphalt Recycling
and Reclaiming Association (ARRA) has presented special recognition
awards to deserving public officials and consulting engineers
for their overall professional contribution to and recognition
and promotion of the asphalt recycling and reclaiming industry.
During its 32nd Annual Meeting, in San Jose del Cabo, Mexico,
in February, ARRA announced the recipient of its 2008 Award
for Excellence in Soil Stabilization. Nominated by John Harvey
Edwards, Site-Prep, Incorporated of North Carolina, the winner
was Tim Antley, Construction Services Manager, Dennis Corporation.
Read
the nominating ballot. |
Fairfield County, SC uses FDR to Upgrade Unpaved
Roads
Fairfield County, S.C. is typical of many rural
counties in America. Located between Columbia, S.C. and Charlotte,
N.C., the county has an area of 700 square miles and a population
of 24,000. Budgets are tight, and the maintenance of approximately
220 miles of unpaved (gravel surfaced) county roads is an ongoing
problem. Although the unpaved roads have low-volume traffic, maintenance
requires frequent blading of the gravel, and the surface aggregate
has to be replenished on a regular basis (costing the county about
$200,000 per year). In addition, the citizens are faced with lower
quality roadways, with dust and other associated problems of unpaved
surfaces.
Dennis Corporation, an engineering consulting
firm based in Columbia, S.C., was looking for a solution to help
Fairfield County’s Transportation Committee upgrade the road
conditions in a cost-conscious manner. They suggested full-depth
reclamation (FDR) using cement as a means of rehabilitating failed
asphalt pavements. The South Carolina DOT has been using FDR with
cement for more than 10 years with excellent results, and the Dennis
Corporation thought the same procedure could be used on the county’s
gravel roads.
Their plan was to upgrade the gravel roads to a bituminous surface
treatment (chip seal), which would provide a smoother, safer road
surface and eliminate the problems with dust and the expensive maintenance
of blading and gravel replacement. The FDR process on the gravel
road would make use of the existing gravel by blending it with cement
and subgrade materials to a depth of 6 inches. This cement-stabilized
material would make an excellent base for a triple bituminous surface
treatment (or a thin asphalt surface).
The cost evaluation showed that the FDR process, with the surface
treatments, would save the county over $70,000 dollars per mile
compared to the alternative of a standard asphalt pavement with
2 in. surface and 6 in. aggregate base (see table below). This cost
savings would allow the county to upgrade 3 miles of road using
the FDR with cement process for every 2 miles of asphalt pavement
that could be constructed at the same cost.
In September of 2006 the county contracted with Site Prep Inc.
(Monroe, N.C.) to perform the upgrading of 14 sections of unpaved
road in different locations around the county (totaling 13.5 miles).
The design called for 33 lbs. of cement per square yard of roadway,
mixed and compacted to a depth of 6 in. The FDR process would also
allow the road template to be improved by establishing road crown
and shoulders, which would improve drainage and road safety.
Construction was completed at the rate of 1,500 – 2,000 feet
per day, with a single treatment of chip seal applied the same day
(to provide protection for the new base, and a better surface for
residents to travel on during construction). After completion of
each section a double chip seal was applied to complete the triple
surface treatment.
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| Mixing cement during the FDR process. |
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| Improving the road template. |
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| Application of bituminous surface treatment
(chip seal). |
The county was extremely pleased with the final product, especially
considering that the cost savings allowed more miles of roadway
to be improved. Dennis Corporation President, Dan Dennis, PE stated
“…we were able to save the taxpayers approximately $1.5
million and improve their quality of life by paving existing dirt
roads that many citizens had driven on their entire lives”.
The fact that the road base is cement stabilized will improve the
long-term performance of the reconstructed sections, since the higher
strength base can carry heavier loads and is much less susceptible
to water damage than stone base. The county was so impressed by
the process that they are planning to upgrade 16 more miles in their
roadway improvement program for 2007. By making improvements each
year, it won’t take long for the county to substantially increase
the quality of their road system, and make excellent use of their
scarce resources by stretching those construction dollars.
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