?This project represents an ongoing partnership with TDOT,? Chambers says. ?We?re trying to get them to write some new specs for increasing the amount of RAP (reclaimed asphalt pavement) allowed in state projects.?
Currently, Tennessee limits RAP content to 30 percent in binder mixes and 10 percent in surface mixes.
?Tennessee is looking at ways to cut the overall cost of paving and they asked us and we told them RAP is a viable solution,? Chambers adds. ?On the Hwy. 266 project we took a value engineering approach in showing TDOT how to save money. We told them a high-RAP warm-mix design could save $7 per ton and we were willing to split that savings with them.
?We were able to write a contract without an escalation clause to cover the rising cost of liquid AC binder because we knew we would use less binder by increasing the RAP content of the mixes required for the project,? he adds.
The 14,000-ton project represented a $98,000 savings by going with a high-RAP WMA design. LoJac placed a 2 1/4-inch-modified binder course containing 50-percent RAP followed by a 1 1/4-inch surface course containing 30-percent RAP. The mix was produced at the company?s Lebanon facility using a portable screen to fractionate (separate) the RAP into -5/16 and -3/4 inch aggregate for use in the binder, and -5/16 and -1/2 inch aggregate for use in the surface mix. Fractionating RAP allows it to be handled like virgin aggregate when it is blended back into the new mix. The plant was also retrofitted with an Astec Green Double Barrel system to foam the warm mix.
?The warm-mix technology enables us to increase the RAP percentage because of the lower temperature required in the foaming process,? Chambers notes. ?When adding RAP in a hot mix design the aggregate is heated at a much higher temperature to ensure adequate coating of the AC. The higher temperature tends to overcook the RAP, which releases more blue smoke. But with the warm-mix technology, the foaming process expands the (liquid) asphalt and allows you to achieve adequate coating of the rock at a much lower temperature.?
The ability to produce mix at 250 to 275 degrees F versus 325 to 350 degrees F also provides a much better working environment for plant and paving personnel.
?We know the air quality is better at both the plant and the paver, and that?s not only good for the environment, but also good for our employees,? Chambers states. ?And besides the health benefits for our employees, we know we?ll save between 12 and 14 percent in fuel costs to produce warm mix versus hot mix, and we?ve been able to eliminate a roller when placing warm mix because we can achieve compaction a lot faster.?
For TDOT, writing new specs to increase RAP in WMA designs represents a significant savings. According to Chambers, TDOT placed approximately 2 million tons of asphalt in 2007. New mix design specs that allow high-RAP warm mix to be used represent millions of dollars in savings.
So you can see why Don Chambers sees high-RAP warm mixes as a ?win-win-win? proposition for LoJac, its customers and the industry in general
?Sustainability is the key to addressing the infrastructure needs of this country,? says Chambers, who wants to see the industry become a leader in the ?green? effort in using sustainable materials and practices. ?High-RAP WMA saves energy, rock and AC. It?s good for the environment, for our workers, for our customers and for our industry. It just makes sense.?