Launch Slideshow

Placement begins. The mixture is spread along the straight edge that was prepared earlier. Note that the RCC is placed about 2 inches thicker than the material from yesterday so that it can be compacted that amount to end up at the same elevation.

Suburb self performs RCC

Suburb self performs RCC

  • Next step: compacting the new RCC to the same thickness as the previously placed material. Four passes with a 10-ton Ingersoll Rand DD-90; two with vibration, two without. Prairie Material uses ASTMs D1557 modified Proctor test on both mix design and materials to determine optimum moisture and density.

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    Next step: compacting the new RCC to the same thickness as the previously placed material. Four passes with a 10-ton Ingersoll Rand DD-90; two with vibration, two without. Prairie Material uses ASTMs D1557 modified Proctor test on both mix design and materials to determine optimum moisture and density.

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    PW Staff

    Next step: compacting the new RCC to the same thickness as the previously placed material. Four passes with a 10-ton Ingersoll Rand DD-90; two with vibration, two without. Prairie Material uses ASTM’s D1557 modified Proctor test on both mix design and materials to determine optimum moisture and density.
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    PCA/Wayne Adaska

    Reflective transverse crack through asphalt surface.
  • Prairie Material of Bridgeview, Ill., delivers the mix  400 pounds of cement and 125 pounds of fly ash with BASF Construction Chemicals Delvo hydration stabilizer  to a Blaw-Knox asphalt paver. The mixture reaches 6,000 to 10,000 psi at 28 days. Materials producers are getting better and better at producing a mix that wont fail, says Public Works Director Matt Mann. The reason: Theyre using a new type of equipment  ribbon mixers -- instead of pug mills.

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    Prairie Material of Bridgeview, Ill., delivers the mix 400 pounds of cement and 125 pounds of fly ash with BASF Construction Chemicals Delvo hydration stabilizer to a Blaw-Knox asphalt paver. The mixture reaches 6,000 to 10,000 psi at 28 days. Materials producers are getting better and better at producing a mix that wont fail, says Public Works Director Matt Mann. The reason: Theyre using a new type of equipment ribbon mixers -- instead of pug mills.

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    PW Staff

    Prairie Material of Bridgeview, Ill., delivers the mix – 400 pounds of cement and 125 pounds of fly ash with BASF Construction Chemicals’ Delvo hydration stabilizer – to a Blaw-Knox asphalt paver. The mixture reaches 6,000 to 10,000 psi at 28 days. “Materials producers are getting better and better at producing a mix that won’t fail,” says Public Works Director Matt Mann. The reason: They’re using a new type of equipment – ribbon mixers -- instead of pug mills.
  • Tim Dunne from materials consulting firm Rubino Engineering Inc. of Elgin, Ill., uses a Troxler 3430 surface moisture density gauge to test the pavement. He says theyve been getting better than the required 98% density.

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    Tim Dunne from materials consulting firm Rubino Engineering Inc. of Elgin, Ill., uses a Troxler 3430 surface moisture density gauge to test the pavement. He says theyve been getting better than the required 98% density.

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    PW Staff

    Tim Dunne from materials consulting firm Rubino Engineering Inc. of Elgin, Ill., uses a Troxler 3430 surface moisture density gauge to test the pavement. He says “they’ve been getting better” than the required 98% density.
  • Feathered edges create a weak joint, so a wheel loader cuts a straight edge between one stretch of RCC and the next, ensures concrete on both sides of the joint is full thickness and properly compacted.

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    Feathered edges create a weak joint, so a wheel loader cuts a straight edge between one stretch of RCC and the next, ensures concrete on both sides of the joint is full thickness and properly compacted.

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    PW Staff

    Feathered edges create a weak joint, so a wheel loader cuts a straight edge between one stretch of RCC and the next, ensures concrete on both sides of the joint is full thickness and properly compacted.
  • A public works crew uses asphalt paving equipment to rebuild residential streets using roller-compacted concrete (RCC), a process theyve perfected over the last five years.

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    A public works crew uses asphalt paving equipment to rebuild residential streets using roller-compacted concrete (RCC), a process theyve perfected over the last five years.

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    PCA/Wayne Adaska

    A public works crew uses asphalt paving equipment to rebuild residential streets using roller-compacted concrete (RCC), a process they’ve perfected over the last five years.
  • A crew member sprays a mixture of water and BASFs Confilm along the edge to keep it moist until the adjacent lane can be placed.

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    A crew member sprays a mixture of water and BASFs Confilm along the edge to keep it moist until the adjacent lane can be placed.

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    PW Staff

    A crew member sprays a mixture of water and BASF’s Confilm along the edge to keep it moist until the adjacent lane can be placed.
  • Placement begins. The mixture is spread along the straight edge that was prepared earlier. Note that the RCC is placed about 2 inches thicker than the material from yesterday so that it can be compacted that amount to end up at the same elevation.

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    Placement begins. The mixture is spread along the straight edge that was prepared earlier. Note that the RCC is placed about 2 inches thicker than the material from yesterday so that it can be compacted that amount to end up at the same elevation.

    600

    PW Staff

    Placement begins. The mixture is spread along the straight edge that was prepared earlier. Note that the RCC is placed about 2 inches thicker than the material from yesterday so that it can be compacted that amount to end up at the same elevation.
  • After testing RCC in a heavy equipment parking area, the Illinois public works department now rebuilds at least one residential street a year using 6 inches of RCC topped with 2 inches of asphalt.

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    After testing RCC in a heavy equipment parking area, the Illinois public works department now rebuilds at least one residential street a year using 6 inches of RCC topped with 2 inches of asphalt.

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    PCA/Wayne Adaska

    After testing RCC in a heavy equipment parking area, the Illinois public works department now rebuilds at least one residential street a year using 6 inches of RCC topped with 2 inches of asphalt.
 

In January, Illinois became the latest state DOT to adopt a paving specification for roller-compacted concrete (RCC), a very dry concrete mix with ¾-inch aggregate that’s delivered by dump trucks, placed with an asphalt paver, and compacted with a vibratory roller. Because of its high density and low water content, the material achieves high strength more quickly than conventional concrete pavement mixes.

RCC is often topped with a thin layer of asphalt. The result is a pavement that’s more durable than full-depth asphalt with a stone base course and easier for self-performing municipalities to finish and repair than conventional concrete pavement.

By approving RCC “for constructing pavement, shoulder, base course, and base course widening” as part of its Experimental Feature Program, the Illinois DOT (IDOT) was able to add RCC to its sanctioned paving practices relatively quickly.

Cities and counties can begin building roads with RCC on any project they like without having to wait for IDOT to conduct a full test project to evaluate material costs, pavement performance, and other data. More importantly, they can receive state motor fuel tax funds for projects. However those that do must provide documentation that will allow the state to track parameters, including materials, curing methods, and joint layout. They will also be required to report on their project’s long-term performance.

“It’s not a particularly fast way of getting things done, but it allows contractors and specifiers to get some experience and helps prevent the blind adoption of the latest fads or trends in road construction,” says Randell Riley, P.E., executive director of the Illinois Chapter of the American Concrete Pavement Association and contributor to the IDOT specification. The association also plans to release an RCC guide specification this summer for use by public agencies and specifiers.

Wayne Adaska, another contributor and director of pavements for the Portland Cement Association, was impressed with the speed at which IDOT reviewed and approved the new provision, a process that took only a few months. He credits the support of the concrete industry and IDOT’s diligence and cooperative spirit for helping expedite the process.

Adaska has worked with many federal, state, and local agencies in developing specifications for RCC. He is aware of at least 14 states and municipalities that have implemented specifications within the past decade. “More and more states are stepping up to the plate in providing RCC as another pavement option for their cities and counties,” he says. (For an interactive map of RCC projects in the U.S., see the RCC Explorer map at http://rcc.acpa.org.)

In Illinois, the floodgates seem to have opened since IDOT published its specification. In June 2014, IDOT plans to accept bids on a project for RCC shoulders, topped with asphalt, in the Chicago suburb of Lemont. The Illinois Tollway has also adopted an RCC specification and will be soliciting bids for truck parking areas in four oasis projects.

Four Chicago suburbs—Berwyn, Des Plaines, Franklin Park, and Summit—are considering alley and residential street applications. The third IDOT specification author, Theron Tobolski, is an adviser on these projects and, as a marketing product specialist for Bridgeview, Ill.-based concrete producer Prairie Material, has been educating public works agencies, engineers, and contractors since 2010.

“As we continue to see successful projects, the comfort level of the engineers and owners grows as they are more willing to use roller compacted concrete,” he says. Tobolski was instrumental in promoting RCC at the state level by inviting IDOT officials to visit jobsites of one of Prairie Material’s most progressive customers: the Village of Streamwood, Ill.

Durability meets fiscal responsibility

In the midst of Chicago’s coldest winter in 30 years—and almost 80 inches of snow—Matt Mann juggled snowplow schedules, monitored the salt supply, and dreaded frozen water mains. One thing that didn’t keep the public works director up at night in January was wondering if village streets could withstand the weather.

For the last four years, Streamwood has invested in rebuilding its neighborhood streets with RCC, topped with asphalt. After reading about RCC in Concrete Construction magazine, Mann and former public works director, John White, proposed the paving method to city council as a cost-saving measure. “We needed another tool in our toolbox, and we knew other states had used it successfully,” says Mann.

When he compared the cost of a typical full-depth asphalt street built to Streamwood’s standards (10 inches of hot-mix asphalt over 4 inches of stone) to an RCC base and asphalt overlay (4 inches of stone and 6 inches of concrete topped by 2 inches of asphalt), Mann estimated the village would save 15% to 20% on materials, plus the labor required to excavate the 2 extra inches required for a full-depth asphalt road.

With the council’s approval, the department tapped into Streamwood’s roadway maintenance funds to put the idea to the test. “About 20 years ago, our roads were so bad that the village appropriated a percentage of telecom tax to devote to maintaining our 100 miles of streets,” says Mann. Local funds allowed public works to use the $1.5 million generated to try out RCC in the absence of a state specification.

The first step, finding a concrete producer, proved to be the most challenging. Rather than following the usual bid process, Mann contacted local producers directly. “It took a few years, but Prairie Material ended up being the only one who could supply us with RCC,” Mann says.

RCC was relatively new to Prairie Material at the time, so the producer and public works department worked together to develop the ideal mix: 525 pounds of cementitious materials, ¾-inch maximum size aggregate, and BASF Construction Chemicals’ Delvo hydration stabilizer.

Prairie began producing the mix with a central batch plant, mixing 5 cubic yards every 90 seconds. To meet the schedule of Streamwood’s larger projects, the producer later bought two horizontal shaft spiral blade mixers, or ribbon mixers, from Dallas-based Vince Hagan Co. to produce more consistent material at a rate of eight cubic yards in 30 seconds.

Next Page: First test project