Roller-Compacted Concrete (RCC)
Roller-compacted concrete, or RCC, is named from the construction method used to build it. It's placed with conventional earthmoving or paving equipment, then compacted with vibratory rollers. RCC is used for mass concrete applications, such as constructing a dam, or in relatively thin flat layers such as a pavement.
RCC has the same basic ingredients as cast-in-place (CIP) concrete: cement, water, and aggregates, such as gravel or crushed stone, and sometimes supplementary cementitious materials (SCMs) and/or chemical admixtures. But unlike CIP concrete, RCC is a “zero slump” mixture that is stiff enough to be compacted by vibratory rollers. RCC can be constructed without joints, formwork, finishing or steel reinforcing. These characteristics make RCC simple, fast, and economical.
RCC began to be used in the 1970’s when the Canadian logging industry switched to environmentally favorable land-based log-sorting methods. The industry needed a strong pavement to stand up to massive loads and specialized equipment. However, economy was equally important because log-sorting yards could span 40 acres or more. RCC met this challenge and has since expanded to other pavement applications such as port, intermodal, and military facilities; parking, storage, and staging areas; streets, intersections, and low-speed roads.
Also in the 1970’s in Pakistan, the first major application of RCC for a water resources project took place at Tarbela Dam. RCC was successfully used to repair erosion of the bedrock lining of the stilling basin for the service spillway. Over 1.1 million cubic yards of RCC were used for the repair and to provide erosion protection for the flip bucket spillway which had a capacity of 650,000 CFS (which is equivalent to the water in 7.3 Olympic-sized swimming pools going by every second!).
One of the key benefits of RCC is that it is a high-volume, high-speed construction method. Normally, RCC is blended in continuous-mixing pugmills at or near the construction site. These high-output pugmills have the mixing efficiency needed to evenly disperse the relatively small amount of water used. The RCC is then transported to the placement areas where it is spread out into a flat layer or lift between 4 and 12 inches thick.
Compaction is the most important stage of construction and begins immediately after placement and continues until the RCC meets density requirements. Curing ensures a strong and durable RCC. As with any type of concrete, curing makes moisture available for hydration which is the chemical reaction that causes concrete to harden and gain strength. A water cure sprays or irrigates the RCC to keep it moist. A spray-on membrane can also be used to seal moisture inside the RCC, but is not appropriate for all applications.
Low cost, fast construction and superior performance give RCC the economic sustainability that continues to draw engineers, owners, and construction managers. But the need for more environmentally sustainable infrastructure is gaining priority in the United States and around the world. The durability, resilience and long lifespan of RCC provide significant environmental benefits. There are also choices that can be made by the project team related to materials selection and construction methods that can reduce the carbon footprint and improve the project’s environmental sustainability.
RCC is just one of several cement-specific materials. See how it and others can be used in the following applications:
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