| Roller Compacted Concrete
(RCC) was developed in the 1980s. Its primary use to date
has been in new dam construction and the rehabilitation
of existing dams. It has also been used for paving areas
that receive heavy axle loads and has had limited use in
road construction. In
1986, Gears, Inc. was the contractor on one of the first
RCC dam rehabilitations. Spring Creek Dam was the highest
dam in the world to be rehabilitated using this
economically attractive and environmentally pleasing
solution. It was nominated for the Civil Engineering
project of the year. Since that time, we have been
involved in numerous RCC projects including construction
of dams, dam rehabilitations, and paving.
RCC is not only a
relatively new product, but RCC construction requires new
construction techniques. Examples include mixing of a no
slump concrete, external compaction of the no slump
concrete utilizing vibratory steel drum rollers, and the
continuous placement of RCC so that the resulting product
is a monolithic block. The basic RCC mix consists of a
graded aggregate or aggregates, cement (a pozzolan may
also be included) and water. RCC, When properly mixed and
placed, takes on the properties of conventional concrete.
Placement is accomplished utilizing conventional
construction equipment. In dam construction or dam
rehabilitation, the RCC mix is generally spread with a
dozer in level lifts and compacted with a steel drum
vibratory roller. Having a level lift is extremely
important in achieving desired densities as an uneven
lift will result in bridging and pockets of poorly
compacted RCC. Final strength achieved by the RCC is
greatly affected by density. The closer to maximum
density the greater the compressive strength.
Proper protection and
curing of RCC is also important to achieve the desired
end product. Curing not only affects final strength but
influences to a degree the bonding between individual
lifts.
Proper proportioning and
mixing of the various components of the mix is obviously
a significant ingredient of a successful project. The
developed mix design must be constantly duplicated in the
field. Our continuous mixing plants, which are computer
controlled, properly proportion the various additives at
rates of 100 to 1,000 tons per hour. Actual output
depends on the physical properties of the soil, amount
and type of additive, and the desired production rate.
The actual mixing of the
various ingredients is accomplished in a twin shaft
pugmill. The shaft’s lengths vary from 12 to 14 feet
with 52 or 66 paddles, depending on plant model. These
pugmills insure a well mixed, homogeneous product through
a violent mixing action in the pugmill mixing chamber.
This mixer is superior to a drum type mixer when dealing
with low or no slump products. The typical drum mixer
tends to merely fold the material.
As indicated in the jobs
list below, Gears, Inc. has significant experience in the
mixing and placing of RCC
For a list of
Roller Compacted Concrete Projects,
up to 1998 click here:
For a list of
Roller Compacted Concrete Projects,
after 1998 click here:
For contacts, phone
numbers and e-mail addresses, please click here:
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