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