Beyond the Build

Tips from the Field

How Roller Compacted Concrete Helped Us Overcome a Deadline

Roller compacted concrete (RCC) traditionally has a wide scope of use, from airport runways, to roadways and parking areas.

We had the opportunity to use this technique on a project last winter. Our customer needed to move into their building, but the asphalt plants were shut down. We installed RCC in the parking lot, striped it, then came back this spring with 1.5” of asphalt topping. Today they have a great parking lot. We met the client’s timing needs, which was the best accomplishment.

RCC has changed a lot as more refined mix designs and better placing equipment has come on the scene. It’s all about consistency in density and the no-slump concrete, which means no forms, no finishing and no reinforcing steel. Here are a few things we learned:

  • RCC mixes are typically non-air entrained, lower cement content, higher fines and smaller top aggregate. The mix has to be just right from the plant.
  • Concrete needs to be dry enough to support the weight of a rolling compactor and wet enough to be cohesive. Lower paste content makes the concrete shrink less.
  • Once concrete is spread, roll it with a steel drum vibratory compactor. That’s all. No finishing after this is required.
  • At least 98% maximum density should be reached, which will yield somewhere between 5,000 and 7,000 psi with flexural strengths in the neighborhood of 700 psi.
  • Marginal subgrade won’t work because you can’t get the necessary compaction.
  • The open texture of RCC looks more like asphalt than concrete. While we covered ours with asphalt, its light color means it will not be a heat sink.

After getting reacquainted with the technique, it seems there may be opportunities for RCC in street construction. With high compressive and flexural strength, high durability, and low cost RCC makes sense.

What experience have you had with RCC? Do you have any best practices to share?

Merrill Stewart Jr.

Merrill Stewart is Founder and CEO of The Stewart/Perry Company, a commercial building contractor based in Birmingham.