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PUBLIC WORKS: On a Roll

PUBLIC WORKS: On a Roll

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    Photo: Portland Cement Association

    RCC paving is typically placed with a double-tamping paving machine.

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    Photo: California Nevada Cement Association

    Completed in 2002, the 318-foot-high, 2500-foot-long Olivenhain Dam near San Diego is North America's tallest roller-compacted concrete dam. It was completed in less than half the time needed for a concrete or earth-fill dam. Aggregate was produced onsite and concrete was made at a rate of 1000 cubic yards/hour.

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    Photos: Portland Cement Association

    The city of Columbus, Ohio, is using RCC extensively as a base course beneath a smoother asphalt layer. The contractor provides a five-year guarantee on this pavement.

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    Photo: Portland Cement Association

    The stepped RCC armor plating on this dam was designed to accommodate a maximum 12 feet of overtopping.

And the possibility of higher-speed roads is not out of the question. Wayne Adaska, director of public works at the Portland Cement Association, says that as construction techniques improve and top size aggregates are reduced from the typical ¾ inch to as small as ½ inch, RCC pavement surfaces have become smooth enough for medium-speed traffic.

RCC is also used for pavements at composting and recycling facilities. The hard surface keeps recycled materials from being contaminated by gravel and soil, and it stands up to the heavy loads and punishment of the equipment.

American Iron and Metal needed a durable platform for a new metals recycling facility in Levis, Quebec. The company chose RCC for its low permeability, and was able to place the pavement and put the yard back into service within 72 hours.

— Palmer is former editor in chief of PUBLIC WORKS. Newman has worked in the construction industry for more than 30 years as a builder and inspector.

Web extra:

For more information on roller-compacted concrete and its application to public works projects, visit the "Article Links" page.


    All the Right Reasons

    Eleven ways to justify specifying roller-compacted concrete for a major road or water project

  • Low cement content: RCC for pavement applications uses 400 to 600 pounds of cement (or a combination of cement plus fly ash or silica fume) per cubic yard—similar to conventional concrete. However, at these cement contents with low water-cement ratios, compressive strengths of up to 10,000 psi can be achieved—much higher than conventional concrete at the same cement content. For gravity dams, less cement is required to meet the design strength, generally in the range of 200 to 400 pounds/cubic yard.
  • Marginal aggregates: Marginal materials and industrial byproducts can be used successfully, especially for dam projects, as long as the fines content is controlled. Onsite aggregate is often used in dam projects.
  • No reinforcement: The elimination of steel reinforcement represents a significant savings in materials and labor.
  • Simple construction: It's easy to place, and contraction joints in pavements are unnecessary—unless crack control is important to improve appearance. Joints are required, however, in gravity dams to control thermal and shrinkage cracking. Finishing is also not needed, leading to rapid construction and a substantial reduction in labor.
  • High compressive strength: RCC designed for pavements typically yields concrete with up to 10,000 psi, giving pavements high-impact resistance and the ability to handle heavy loads. For most gravity dams, high strength is not needed, leading to low cement contents.
  • High flexural strength: Flexural strength of up to 1000 psi helps pavements span soft spots in the subbase and provide longer fatigue life.
  • Durability: High density and low permeability reduces water absorption, making it more durable and resistant to freeze-thaw damage. Some of these pavements have been in place in eastern Canada for nearly 30 years.
  • Cost: The overall cost beats conventional concrete, and it competes head-to-head with asphalt pavements and earthen-filled dams, providing a better product at an equal or lower cost.
  • Life-cycle cost: The combination of strength and durability leads to less expense for maintenance and repair, and provides longer life cycles, thus lower life-cycle costs.
  • Return to service: These pavements can be used by light traffic much sooner than other pavements, sometimes within a matter of hours. For neighborhood streets, this means residents can usually drive home the same day the pavement is laid. For dam construction, as soon as a lift is placed, machinery can immediately begin work on the next lift.
  • Born green and still green: The invention of RCC was in response to an environmental concern when the Canadian logging industry came under pressure to clean up the waterways they were using for log transport. The solution was to build haul roads that would stand up to the extreme conditions. RCC combines that ability with easy recyclability, and a lighter color that reduces lighting needs and heat island effect.