Roller-compacted concrete pavement (RCC) has been used for several decades in specific applications, mostly for heavy-duty industrial pavements. But it has the drawback of a rough surface with little aesthetic appeal, leading some owners to use it as a subbase with an asphalt overlay.
A contractor and chemical maker may have resolved these issues. They’ve launched an “advanced” form of roller-compacted concrete they’re calling compacted concrete pavement (CCP). Mixed and placed similarly to roller-compacted concrete, proprietary additives plus finishing materials and processes enhance durability, rideability, and appearance.
“We’d been doing roller-compacted work and saw the value of it being fast and durable, but the appearance turned everyone off,” says Matt Munsick. Munsick is vice president of Andale Construction Inc., a civil services contractor in Valley Center, Kan., that’s placed more than 350,000 cubic yards since 2011; and ACEiT Industries Inc., an admixtures developer in Wichita, Kan. “For some industrial applications that’s not a big deal, but for many markets it is.”
This launched the companies on a mission to figure out how to finish a roller-compacted surface, which is too dry for conventional finishing. They tried various finishing aids, modifying as they went along, and finally came up with two chemicals designed specifically for roller-compacted concrete and cement-treated bases: ACEiT Plus, a powder added at the pug mill; and ACEiT Blue, a liquid sprayed onto the surface right in front of the trowels.
The powder stabilizes moisture, reduces viscosity, and inhibits cement hydration until mechanically activated. It “manages the interaction of the cement and water” and also works as a retarder and provides a little entrained air. Without going through the paver, the hydration process doesn’t start. Munsick says mixes have sat in dump trucks for several hours without setting up.
Once placed with an asphalt paver, the compacted concrete gains strength quickly. With very low water content and zero slump, finishing equipment can get onto the slab right away. During finishing, the surface is treated with ACEiT Blue, which is a hydration enhancer, surface tension reducer, and finishing aid. The surface is troweled with riding trowels and pans before typically getting a light brooming.
The result is concrete pavement that’s been shown to have high flexural and compressive strength, excellent freeze-thaw resistance, and reduced permeability to chemical surface attack. It eliminates the need for reinforcing and dowels, which reduces cost and corrosion failure; and provides a well-lit and slip-resistant surface that can be installed using simplified and quick construction techniques.
“With this material and process, you can’t tell the difference between compacted and traditional concrete pavement,” says Munsick.
Government customer gives it a try
ACEiT Industries has begun licensing the process to contractors and selling them the materials. One such contractor is the Wm. Winkler Co. of Newman Lake, Wash. Services include pervious and concrete pavement for airports, highways, and parking lots. To show what could be done, Winkler constructed a 5,000-square-yard prototype project at the Port of Walla Walla’s industrial site in Burbank.
Heavy traffic had caused the asphalt entry road to deteriorate significantly. Seth Walker, PE, an engineer for the Washington Department of Transportation in Walla Walla County, considered rebuilding the road with asphalt and portland cement concrete pavement (PCCP) but opted instead to try compacted concrete.
“In our test pours, we had the opportunity to play with the product’s set times,” says Wm. Winkler President Brian Winkler. “The material was extremely resilient, way beyond what we would expect for conventional or roller-compacted mixes. It was very forgiving; extending placement and finishing times didn’t adversely affect in-place performance.”
This allowed the surface to be mechanically troweled and finished, providing exceptional surface density and abrasion resistance. While the mix design used 15% less cement, initial compressive strengths averaged 4600 psi in four days and 6340 psi at 28 days.
Winkler worked closely with Munsick in the development of mix designs, logistics, mixing, and placement, and finishing. The existing road base and asphalt was pulverized and recycled as cement-treated base. Curb and gutter was installed and then a 7-inch layer of compacted concrete was placed. The project used an on-site Rapid International Rapidmix 400C continuous mixing plant with dump truck delivery and Wirtgen high-density tracked asphalt paver.
The surface was rolled during test placement, but during main-line construction densities right out of the paving machine exceeded compaction requirements without rolling. The high-density paver got 97% to 98% density immediately upon placement. Though not really necessary, Winkler placed sawcuts at 15-foot intervals to satisfy the owner. The contractor also experimented with a broom finish and a transverse tine on some sections, which turned out nicely.
“This is impressive” says Port of Walla Walla Executive Director Pat Reay. “Installation quickness is critical on projects of this type.”
“We’ve taken roller-compacted concrete to the next level,” says Munsick.
“This is the future of pavements providing first-cost and extended life benefits,” says Winkler. “Our clients won’t need 1-800 numbers for pothole repairs anymore. This does what roller-compacted concrete started out to do: provide a viable alternative to traditional concrete. It did that but we just needed, with the help of ACEiT, to extend that benefit to streets, which are a huge infrastructure need.”
