The Texas Success Story is Spreading!
 By
Greg Halstead Pavement Engineer, Portland Cement Association
 As
the lessons learned in Texas are exported across the nation, other
states are beginning to realize that recycling failed flexible pavements
with portland cement has many advantages.
In
today's interest in saving the resources available, this construction
method assures the conservation of non-renewable resources by reusing
the materials that already exist in the roadway It eliminates for
the need for new granular base material, reduces hauling and energy
costs and eliminates bumps, dips, ruts, potholes, cracks and patches.
The
new stabilized base course can be shaped to restore the desired
surface crown and cross-slopes, preserve drainage flow at curb and
gutter sections and retain adequate clearance at overhead structures.
Other
areas of the United States are following the Texas lead in recycling
rural county roads, local streets, and highways. Thousands of miles
of state, county and rural roads in the U.S. are rapidly deteriorating
and in need of immediate rehabilitation. Nearly three-fourths of
these roadways were constructed with flexible-granular base materials
and were often under-designed for the greater and heavier traffic
loads that these pavements experience today Ruts, potholes and severe
cracking are common problems that are usually maintained with asphalt
patches or thin overlays, or often by simply grading and re-compacting
an unsurfaced granular base. These problems cannot always be blamed
on normal wear and most often are the result of a failed or inadequate
base course.
 Salvaging
failed flexible pavements is a good practice because the pavements
still contain good granular material that can be reused and recycled
into a strong, durable new base. A process commonly referred to
as Full-Depth Recycling (FDR), is a technique in which the old asphalt
pavement and a portion of the underlying base, subbase or subgrade
materials are pulverized and blended together to create an enhanced
homogenous base material. FDR is performed on the roadway itself
at depths ranging from 6 to 10 in. depending on the thickness of
the existing pavement structure.
For
decades, many FDR projects have been successfully constructed in
Texas at the state, county and municipal levels - with all benefiting
from the low cost and durability of the recycled roadways.
The success that Texas has experienced is being followed in other
states across the nation as well. For example, a recent project
outside Rock Hill, S.C., was undertaken by the South Carolina Department
of Transportation to address one of its deteriorating roadways.
On this 6.74-mile section of State Route 223, the old asphalt and
base materials were pulverized in place on the roadway mixed with
cement and water and then compacted, shaped and surfaced.
 The
FDR process was performed at one-third the cost it would have been
to remove and replace the existing roadway Like the Texas Department
of Transportation, SCDOT is an ardent supporter of FDR and has approved
specifications for cement stabilized base courses.
Portland
cement is the key to reconstructing flexible pavements that have
failed. The incorporation of portland cement with the old base course
material provides a practical, cost-effective means of strengthening
worn-out pavements. The cement binds the granular particles together
to form a paving material capable of withstanding moisture infiltration
and degradation. It increases the strength of the base without the
need for removing the old material and hauling in large quantities
of expensive new base materials.
Always
on the cutting edge, Texas is one of the leaders in the recycling
industry when it comes to the application of cement in a liquid,
or slurry form. The cement slurry is simply a mixture of water and
cement that is blended together and then applied to the pulverized
material during the recycling process by means of a modified water
truck Applying the portland cement in this fashion helps to reduce
the amount of airborne dust and makes it a preferred method when
working in urban areas.
 The
application of cement to the rehabilitation needs on Texas roads
and highways and the innovations in construction techniques has
re-established an old practice to modem requirements.
Greg
Halstead is a pavement engineer with the Portland Cement Association.
He is responsible for providing design, construction, technical
assistance and guidance for cement stabilized soils, soil-cement
base, roller-compacted concrete and full depth reclamation.
Prior
to the PCA, Greg worked for the Georgia Department of Transportation
in all areas of the DOT involvement. He worked closely with other
departments of transportation, city and county public works departments,
colleges and universities and design and construction personnel.
Greg
is a graduate of Shippensburg Stale University, in Shippensburg,
Pa., and received a civil engineering technology degree from Southern
Polytechnic State University in Marietta, Ga.
 Back
to the top
|
