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.
 

First test project

With the producer onboard, the department began with a test project: paving a section of its own property used for parking heavy-duty equipment and salt storage. It placed 6 inches, compacted it, and left the surface unfinished to monitor its durability. The pavement performed so well, the department didn’t hesitate to use it as a base course for city streets. “We placed the test pad in 2009, and it’s still in good shape,” Mann says.

Although it’s too soon to measure long-term maintenance savings, Mann anticipates repairs will be easier with the RCC-and-asphalt streets. “With the concrete base course, we can go in and mill off the top couple of inches, but we shouldn’t have to do anything else,” he says.

One unexpected development has been the controlled cracking pattern of the asphalt surface over the RCC base. “Typically, when asphalt cracks, it’s in a random way,” says Mann. “But here, we’re seeing surface cracks that mirror the joints we’ve cut in the RCC base course. We still have to seal them, but it’s actually easier since they follow a more predictable pattern.”

This is one reason the village prefers to top RCC with asphalt. According to Adaska, due to the absence of air entrainment, unsurfaced RCC in freeze/thaw environments is more susceptible to surface scaling and frost damage than conventional air-entrained concrete pavement. The rough surface doesn’t pose a problem in industrial areas, but is less desirable for public streets.

When topped with asphalt, however, an RCC road base can last up to 50 years, compared to the 10-to-15-year lifespan of typical full-depth asphalt. “RCC actually improves the life of the asphalt by preventing the fatigue failure that occurs with asphalt on a stone base,” says Adaska.

Adding an asphalt overlay to an RCC base is also easier for public agencies to handle in-house. “Like most cities, we don’t have the equipment to finish concrete pavement, so we’d have to pay a contractor, which would negate some of the cost savings,” says Mann.

Unfinished RCC roads are typically built by counties or state DOTs that can use their own diamond grinding equipment to smooth the surface. “Diamond grinding smooths out the pavement, removes high stops, and provides an improved surface texture for enhanced skid resistance,” says Adaska. “A finished RCC surface also takes advantage of concrete’s higher reflectivity, producing a cooler pavement with reduced lighting requirements.”

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