Roller Compacted Concrete (RCC)

The construction industry today relies heavily on two commonly used materials, concrete and asphalt. They have a long history of use and have proven their usefulness in project after project. So, when a new material comes along, the reaction of most people is, “show me!” However, once in a while a truly exceptional new product does appear. This is the ease with Roller Compacted Concrete (RCC).

Roller Compacted Concrete is similar to concrete, composed of coarse and fine aggregates, cement, fly ash, water, and in some cases water reducing additives. It is, however, mixed in a portable pugmill plant that is put up onsite, rather than being delivered from a commercial batch plant. The pugmill plant is used because it is easily portable, allows for short travel times from plant to placement site, and it allows a steady and continuous flow of materials for high productivity.

RCC is placed like asphalt, with asphalt paving equipment. A steel roller compacts the material to 95–100%. This compaction and a low water/cement ratio makes RCC stronger than concrete without the need for rebar reinforcement. A water fog spray system is then used for curing. Since asphalt pavers are used for placement, less labor is required than for concrete. Because of its strength, less cutting is required to control cracking, and this also reduces labor costs.

Roller Compacted Concrete is the result of experimentation with processing soils or aggregates and cement. It was first used successfully in Australia, where the cost of trucking spec materials to remote highway locations was prohibitive. It was realized that a process could be developed to use onsite, non-spec materials, mixed with cement, to produce a strong and durable pavement.

In the U.S., the process has been refined and developed, but is still relatively new. It is now being used to build dams that need not be reinforced with rebar and can be constructed in layers, with minimal labor and equipment. Projects that at one time took years to complete can now be done in months, and cost savings are significant.

Since RCC is new, there is not the long history of performance in different types of settings and uses that there is for asphalt and concrete. So in deciding whether it is the best material for the job, it is important to consider the site and the materials to be used on the project. Also, project size and location are important factors, due to the cost of setting up a pugmill plant.

Graniterock will work with engineers to provide information on current RCC designs and those now in conceptual stages of development. It is important for engineers to learn more about RCC so that there is a greater awareness of the potential benefits it can bring to pavement design. RCC is a “value added” pavement concept: it enhances the overall performance of a project.