Goodrich agrees, adding, "This HIR method constructs joints very well and repairs pavement to a 'as good as new' level."
(subhead) The reasons for choosing HIR
HIR was chosen for the State Highway 82 project for several reasons says Goodrich. "With a traditional mill-and-fill, you need new aggregate and new oil – virgin material," he explains. "With HIR, you're revitalizing the materials already in place. It's recycling what you have; it's somewhat of a green solution."
HIR also increases the structural value of the pavement, says Goodrich. "With HIR, you have increased strength of the material," he says. "A typical HIR treatment will last up to 10 years, so the longevity is hard to match."
Of course, there is a downside to HIR – the length of the equipment train can be a challenge from a construction standpoint, says Adam Cornely, project engineer with CDOT.
"The total length of the heater remixing equipment train required to perform the operation caused some traffic issues, specifically when performing the remixing in busy intersections," he says. "Traffic is very dense on Hwy 82. It's a major commuter route, so we had to take the traffic impact into consideration. With mill-and-fill, you would need a week or two for milling, then however long for paving, creating two disruptions. While it was a disruption to traffic – it took about an hour to get through some busy intersections – HIR was a better choice for this project."
SMA was chosen as the 1-inch wearing coat choice because it resists rutting, says Goodrich. "SMA is good for protecting against premature rutting and offers a durable driving surface," he explains.
Like Smith, CDOT has fully embraced recycling techniques, such as HIR and CIR (Cold In-Place recycling) and has done several recycling projects on its roads over the years. "Each year, we often have two or three recycling projects going on in my region alone."
As far as State Highway 82, the project went well and hit no snags. "I think the state of Colorado was pleased with the results," says Smith with Paveover. "HIR was the chosen as the best process for that project when the state looked at the cost differences of other processes, traffic impact, etc."
(subhead) Benefits of HIR
Hot In-Place recycling offers both environmental and economic benefits. Here are a just a few.
• 50% reduction in hydrocarbon emissions
• 80% reduction in non-renewable aggregate requirements
• Minimizes use of new non-renewable AC
• Minimizes issues related to storage of asphalt materials
• Reduces traffic congestion and vehicle idle times
• 30-60% cost reduction over conventional mill-and-fills
• Minimum delay times during construction activities
• Recycling process replaces pavement to original elevations so there's no need to treat turn lanes or other less worn travel areas
• Recycling process achieves productivity up to 2 1/2 miles/day
There aren't many disadvantages to using HIR, says Smith. "You can't really do a parking lot with this equipment because the train is too big," he says. "But the greatest benefit of HIR is reusing the resources we already have on the road. We've overlaid our roads enough that there's plenty of good rock and asphalt that we can use again. It's just the right thing to do."