Rapid International Ltd

Rapid International’s mobile continuous mixing plant, the Rapid Mix 400 has been designed to be totally mobile and completely self-contained with its own power source.

An example of this machine being used in a Roller Compacted Concrete (RCC) application is in Columbus, Ohio, USA. RCC construction was first introduced onto the city’s streets in 2001. It has the same ingredients as conventional concrete; cement, water, and aggregates, however, it is a drier mix and stiff enough to be compacted by vibratory rollers. It has the strength and performance of regular concrete yet it is as economical and simple to use as asphalt. It was first used in the seventies in the logging industry in Canada, as they needed strong pavement to stand up to massive loads and heavy equipment having switched to environmentally cleaner, land-based logsorting methods. It’s strength and durability indeed lived up to the job and it has since expanded into other heavy duty applications.

The benefits of using the Rapid Mix 400 with this type of application is that it has the mixing efficiency needed to evenly disperse the relatively small amount of water used. Dump trucks then transport the RCC and discharge it into an asphalt paver, which places the material in layers up to 10 inches (250 mm) thick and 42 feet (13 m) wide.

Compaction begins immediately after placement which is how the concrete attains its level of smoothness, density, surface texture and strength. This stage continues until the density requirements are met.

The final stage is curing where moisture is applied, allowing hydration of the concrete, thus causing it to harden and
strengthen.
In Columbus, Ohio, the RCC was found to be particularly useful under difficult traffic conditions; the required strength of 400 psi was attained within 24-48 hours of placing the concrete.

The construction companies involved in these RCC pavement projects are confident that they can compete head-to-head with asphalt pavements and they also recognise the life-cycle cost savings you get when using concrete.