Consultant Picks RCC for Tough Job

LAN Associates, an engineering consulting firm based in St. Augustine, Florida recently selected roller-compacted concrete (RCC) for one of their industrial clients in the Midwest. The job called for a pavement that could economically cover large areas (at least 10 acres), and hold up to heavy-duty abuse from large equipment. This was a job particularly suited for RCC.

Dan Vipperman, Project Engineer for LAN Associates, did a thorough investigation of RCC before selecting it for the project. “This is the first time we specified RCC for a project, so we needed to become familiar with the material and the design elements,” Vipperman said. He worked with S&ME engineers at their Louisville, Tennessee office to experiment with different mix designs. A dense-graded crushed stone aggregate was selected that had a nominal maximum size of ½ inch. The smaller aggregate gradation would provide a smoother surface for the heavy equipment and trucks that would be operating on the RCC.

Vipperman was also interested in a blended cement, since the surface of the RCC would be subjected to equipment scraping and needed to be especially durable. He eventually selected Teracem, a ternary cement supplied by Lafarge North America that is a blend of 75% portland cement, 20% slag cement, and 5% silica fume. He asked S&ME to investigate the effect that the Teracem might have on the compaction of the RCC, and found that the mix was slightly more sensitive to changes in moisture content than straight portland cement.

The mix design selected for the job used 13% Teracem at an optimum moisture content of 6.4 %. This mix provided compressive strengths of 5,500 psi in 7 days, and 8,000 psi in 28 days.

LAN Associates performed the pavement design with the assistance of PCA’s RCCPave computer program. Vipperman wanted to keep the construction to one lift in order to simplify the construction process. The original designs for RCC on subgrade called for approximately 11 inches of thickness, which is excessive for one-lift construction. An alternative of 9 inches of RCC over 4 inches of cement-treated base (CTB) proved to be adequate, and since the 9-inch thickness could be placed in one lift this design was selected. For the CTB, a dense-graded aggregate with 4% Teracem provided 1,000 psi compressive strength in 7 days.

Using CTB for a RCC pavement is not new, and contractor A.G. Peltz of Birmingham, Alabama has used it extensively. “We used CTB under a lot of the RCC we placed at the Honda manufacturing plant in Alabama” said Ron Peltz, a partner with the construction company. “It is pretty economical to place, and it provides a great platform for RCC paving.” Approximately one million square yards of RCC was placed at Honda, the largest RCC project to date in North America.

LAN Associates contracted with A.G. Peltz for construction of their industrial project, and work began in March of 2005. Peltz set up an Aran pugmill on site, and a nearby Vulcan Materials quarry provided the aggregate. Initial cylinders taken during construction had 3-day compressive strengths of 3,400 psi, so the material is performing as expected. “We think that RCC is going to work well for this project,” said Vipperman, “and we are anxious to put it to the test.”

More about RCC:

Features & Benefits of RCC Pavements
Related RCC Links
Research in Progress
RCC FAQs
Paver-Compacted Concrete
RCC for Ports
Recent Projects

 
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