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Roller-Compacted Concrete> Atlanta
I-285 Georgia Department of Transportation
Rolls out RCC on Interstate Shoulders
By Matthew W. Singel, P.E.
 In
recent years, the Georgia Department of Transportation has spent
time investigating roller-compacted concrete (RCC) pavement and
its potential value to their program. The speed of construction,
durability, and economy offered by roller-compacted concrete pavement
are attributes that made it a long-term solution for GDOT pavement
management. When the west side of I-285 came due for rehabilitation,
RCC represented a logical choice for the reconstruction of the failing
shoulders.
Spanning 17.3 miles along the west side of Atlanta’s Perimeter
Beltway, the I-285 project consists of concrete pavement rehabilitation
(select slab replacements) on the mainline, and reconstruction of
the outside shoulders both northbound and southbound. The general
contractor for this project is Pittman Construction Company, based
in Conyers, Ga. The mainline slab replacements are being performed
by Costello Industries, Inc., College Park, Ga., with the RCC paving
being handled by A.G. Peltz, LLC, Birmingham, Ala.
Traffic volume and minimizing impact to the traveling public are
always serious considerations for the GDOT when evaluating any improvement
project. The necessary one-lane closures for RCC construction started
at 9 p.m. Friday evening and continued through 5 a.m. Monday morning,
with the option of limited working hours at night Monday through
Thursday .
Removal of the existing failed shoulders began Friday evenings
with the milling and removal of the existing asphalt and subbase
material to 11 ½ feet wide. The units use a grade control
system to provide the required depth of removal at the mainline
pavement edge and slope control to hold the depth at the outside
edge. This equipment allows for the removal of 1.5 to 2.0 lane-miles
of shoulder material between 9pm on Friday and 5 am on Saturday
(an 8 hour period). Milled asphalt from the project is discharged
directly into trucks for subsequent hauling to local interchanges,
where it is being used for improvements.
Placement of the new RCC shoulders began early Saturday mornings
and wound down each Sunday in order to make the highway ready for
Monday morning traffic. The shoulders were constructed 10 feet wide
with depths of 6 inches and 8 inches as indicated by the GDOT design.
 The
RCC material was manufactured on-site in a continuous pug-mill operation.
This unit produces RCC at rates of up to 500 tons per hour (250
cubic yards) to meet the demands of the paving crew.
The RCC mix design was developed by A.G. Peltz, LLC, in conjunction
with CMS Labs of Locust Grove, GA and approved for use through the
GDOT Office of Materials and Research. The aggregate was adensely
graded blend of fine and coarse aggregates with a nominal maximum
size of ½ inch with cement and water rounding out the mix.
 The
paving operation consisted of an ABG Titan high density paving machine
with a dual tamping bar in the screed. This machine has the capability
of paving to a width of more than 40 feet and nearly 10 inches per
lift while achieving densities of up to 95 % (modified proctor)
density. This paving unit was used in conjunction with a Gomaco
Material Transfer Vehicle to ensure a consistent flow of material
which, ultimately, contributed to an improved ride quality.
Compaction immediately followed placement, with a 10-ton Hamm oscillating
steel drum roller and an Ingersoll-Rand combination roller both
staying busy throughout the operation. The rolling pattern was established
using a nuclear density gauge with a target of 98% density. This
was accomplished using the roller in a combination of vibratory
and static modes.
Immediately after placement and compaction, nuclear density tests
were performed. The project required a 98 percent average density
with no test below 95 percent. Additionally, the specification called
for a surface smoothness not exceeding ¼ inch deviation under
a 10-foot straight edge.
.
 The
paving contractor completed the RCC placement process with an application
of a white pigmented curing compound which allowed the RCC to retain
the moisture required to build strength quickly. This curing compound
was applied with a custom, wheel mounted, tank and spraybar unit
for easy and uniform application.
Within the first two hours of placement, an early entry (Soff-Cut)
saw cut contraction joints to match the adjacent mainline pavement.
Joint sealing and grinding of rumble strips completed the process
and provided a shoulder pavement that will have long-term performance.
As traffic volumes steadily increase and funding is continually
stretched, roller-compacted concrete is becoming a pavement of choice
for many applications. Its economical price, long-term performance,
low maintenance and quick return to traffic have positioned RCC
pavement as a value-engineered material that should be well suited
to many applications.
Matthew W. Singel, P.E., is specialty pavements engineer with the
Southeast Cement Association. He may be reached at matt@secement.org
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