Better Roads

November 2013

Better Roads Digital Magazine

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ticles, composed of cement paste plus sand particles and fly ash or any other admixture. How much mortar should come off the RCA depends on the ultimate use of the RCA. Again, the RCA needs to be tested and treated as an engineered material. Some types of crushing processes will remove less mortar, but then the presence of added mortar will have to be taken into account in designing the application. The other end of the spectrum is reclaiming less material while producing an RCA that is as close to natural aggregate; for that, an impact crusher will remove as much mortar as possible. Stockpile management with RAP Good materials management practices should always be part of the quality-control program for any asphalt mix production operation, says NCAT's West. "As RAP contents increase, it becomes more important to accurately determine properties of RAP and control its consistency," he adds. Sadly, while dirt and trash are a common component of demolition concrete submitted for recycling, it can be a problem with RAP as well. In his 2010 draft technical paper, Reclaimed Asphalt Pavement Management: Best Practices, West suggests keeping dirt and trash out of RAP stockpiles. "It is easy to understand how bad perceptions of RAP form when there is dirt, rubbish or vegetation in RAP stockpiles or when trash is found in the mix when it shows up on the job site or pops out of the pavement a few days after paving," West says. "Treat RAP stockpiles as the most valuable material on the plant yard, because they are." RAP management should begin with a basic inventory analysis of the available RAP and future mix production, West says. This analysis is important to establish realistic goals for how much RAP can be used at a particular plant. The analysis includes the following steps: customers be used amount of RAP needed. When stockpiling RAP, West recommends not building steep stockpiles; this promotes segregation of sizes as large particles roll down the sides to the bottom. "Building steep AMERICAN TRAFFIC SAFETY SERVICES ASSOCIATION CERTIFICATION BENEFITS Commitment and dedication to safety Improves career opportunities Enhances competitive advantages Compliance with state mandates Establishes industry recognition Professional development ATSSA's All New Online Flagger Course Coming Soon! | 877-642-4637 Better Roads November 2013 23

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