VOL 20 ISSUE #2

In the construction industry, there are several factors to consider when you're performing contract work—or any work, really: agency timing issues, production timing issues, subcontractor issues, etc. As Richard Champion, regional sales manager at CEI Enterprises Inc., puts it, "It's an expanding matrix where each additional player you add just expands the Rubik's cube of possibilities in terms of getting everybody scheduled." Adding another log to the fire, say an outside blender, is an added stressor no contractor needs. And, indeed, Matich Corporation felt the same way.

Matich, an engineering contractor/asphalt producer company in Southern California, knows just what it's like to have to rely on outside blenders with outdated equipment. After some less than stellar experiences, Matich made the decision to expand and purchase its own rubber-blending plant. The decision wasn't made lightly; as a smaller, family owned company, Matich had to weigh the cost output versus the potential cost savings. Potential cost savings won and, in the end, Matich bought CEI's Asphalt-Rubber Blending System in 2012.

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RHMA GAINS POPULARITY

Rubberized hot-mix asphalt (RHMA) is making its way through the ranks in popularity—and by law in California—and for good reason. According to Clemson University, "Depending on the application selected, between 500 and 2,000 scrap tires can be used in each lane mile of pavement. This means that for a one-mile section of a four-lane highway, anywhere between 2,000 and 8,000 tires can be used in creating a safer, quieter, longer lasting road." Clemson University further reports:

  • A reduction of reflective cracking in asphalt overlays
  • A reduction in maintenance costs
  • Increased resistance in new pavement cracking
  • Increased resistance to rutting in new pavement
  • An increase to pavement life
  • An increase to skid resistance
  • A reduction of noise level (by up to 5 decibels)

"Because of the open-grade nature of the mix, it has some good characteristics as far as shedding water," added Champion. "Even though the mix itself can be a little bit more expensive on a cost per ton basis, it isn't expensive when you consider the thin lift overlay capability and longevity of the material."

The benefits of RHMA are the reason California requires its use by law and these requirements are one of the reasons Matich purchased CEI's Asphalt-Rubber Blending System. When an increasing amount of contracts require RHMA, having access to a rubber-blending system with state-of-the-art equipment becomes necessary.

RUBBER BLENDING SPECS

RHMA is made using well-ground tire rubber. Champion explained: "California is a little bit unique because they specify a course rubber at about a 20-30 mesh gradation; they also specify that part of the recipe be a high natural rubber, which has a higher rubber polymer content. That's basically a higher grade of tire rubber and that runs about 30-40 mesh."

The key to rubber blending, apart from the rubber, is the rubber-blending system. CEI's Asphalt-Rubber Blending System is a portable asphalt-rubber blending plant comprised of a portable mixing unit and a reaction tank. The portable mixing unit mixes the ground rubber with liquid asphalt, while the reaction tank agitates and stores the mixture. The mass measurement controllers and fully automated PLC control system enable minimal amount of operator functions.

Once the rubber blending is complete, the mix goes to the asphalt plant where it is incorporated into the various asphalt mixes. The RHMA is more viscous, however, than a 76-22 polymerized asphalt. "It's a little harder to work and it's very sticky, but that's because it has the flexibility and viscosity that it does," said Champion.

POSITIVE RESULTS

Matich Corporation was happy with the result of purchasing the rubber-blending plant from CEI. Not only were the potential savings there, alleviating the hassle with outside blenders was a relief. The state-of-the-art facility provided by CEI has only had minor software updates since going to Matich. These conditions are a far cry from what Matich had to deal with before buying the rubber system in 2012.

  • CEI Asphalt-Rubber blending systems used in California feature state-specified twin hoppers that feed metered amounts of two different grades of crumb rubber to the unit’s mixing tank.

  • The portable reaction tank can be a single, double, or triple compartment design. Each compartment has individual controls for level and temperature. For example, one compartment in the portable holding tank contains fresh mix for a specified time while aged mix is used out of another compartment to make hot-mix asphalt. Each compartment has an auger mounted horizontally in its lower compartment. The auger agitates the mix to keep crumb rubber in suspension.

  • CEI’s asphalt-rubber blending plant has automated PLC controls with “recipe-driven” logic to simplify operator functions.

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