| With the assistance of the Portland
Cement Association (PCA), a 1000-foot demonstration section of
Roller Compacted Concrete (RCC) was placed on Powell Pond Road in
Aiken County in March 2002. The material was produced by Lafarge
and placed by C. Ray Miles Construction Company to a depth
of six inches. The Research and Materials Laboratory will monitor
this section over the next several years to observe its performance.
According to the PCA, the first use of RCC was to
pave logging facilities in Canada during the mid-1970s when dry land
log sorting was made mandatory in British Columbia. RCC has also
been used extensively by the US Army Corps of Engineers to pave
hardstands for tanks due to its ability to withstand the turning and
scuffing motions of tracked vehicles.
The largest RCC paving project
was the Saturn Automobile manufacturing facility in Spring Hill,
Tennessee, when 135 acres of roads, parking and staging areas were
paved in the late 1980s and early 1990s.
RCC is a stiff, zero-slump concrete mixture with
the consistency of damp gravel and is comprised of aggregates,
Portland cement and water. It is similar in concept to the SC DOT's
cement content. The mixture is placed using a modified asphalt paver
and roller compacted with the same commonly available equipment used
for asphalt pavement construction to 98 percent of maximum
theoretical density as measured by AASHTO T180.
The process requires
no forms, finishing, or surface texturing. Although many RCC paving
projects do not have sawed contraction joints, single saw cut joints
were placed at 30-foot intervals on the demonstration project to
avoid unaesthetic cracking.
Once cured, the specifications require
that the RCC develop a compressive strength of at least 5000 psi in
28 days. However, on the demonstration project, strengths of over
3000 psi were developed in three days and strengths over 5000 psi
were developed in seven days. Tests performed on other RCC projects
indicate that the flexural strength of RCC is equivalent to
traditional paving concrete.
It is hoped that RCC can provide an economical
paving alternate in lower volume applications where substantial
heavy truck traffic is expected. It also may have applications as a
heavy-duty base course when placed under approximately 400 psy of
asphalt surface and intermediate courses.
Eight inches of RCC is
expected to have the structural capacity of 1000 to 1200 psy of
asphalt aggregate base, can be placed in one lift, and can be
temporarily used by automotive traffic within a few hours of
placement.
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