Equipment World Digital Magazine
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in the use of RAP, RAS and warm mix asphalt technologies from 2009 through 2013. "The asphalt industry remains the country's number one recycler by recycling asphalt pavements at a rate of over 99 percent, and for the first time all (100 percent) contrac- tors/branches report using RAP in 2013," the survey says. The average percentage of RAP used in asphalt mixtures has increased from 16.2 percent in 2009 to 20.0 percent in 2013, and that year the estimated RAP tonnage used in asphalt mixes was 67.8 million tons. "Assuming 5 percent liquid as- phalt in RAP, this represents over 3.4 million tons (19 million barrels) of asphalt binder conserved during 2013," the report says. "The esti- mated savings at $600 per ton for asphalt binder is $2.04 billion." Use of both manufacturers' scrap and post-consumer asphalt shingles used in asphalt mixes increased 135 percent since 2009 to more than 1.6 million tons in 2013, according to the survey. "Assuming a conserva- tive asphalt content of 20 percent for the RAS, this represents about 320,000 tons (1.7 million barrels) of asphalt binder conserved," NAPA reports. "The estimated savings at $600 per ton for asphalt binder is $192 million." The Asphalt Institute (AI) is on record saying the components of RAP have value – particularly true of the asphalt binder – and that the residual asphalt can reduce the amount of new asphalt binder in a mixture. A mix with 20 percent RAP bearing five percent asphalt content can result in a one percent savings in new asphalt binder, AI says. Intangible values Moreover, there are intangible benefits to use of RAP and RAS in pavements. A variety of "green" cal- culators are available that will help agencies and engineers determine the degree of environmental sus- tainability a road project will have. These externalities don't figure into the per-ton cost of asphalt containing RAP or RAS, but they are important as government agencies figure the environmental impact of road construction into the total package. A project's content of recycled materials – and future recyclability in reconstruction – may figure in the choice of whether an July 2015 | EquipmentWorld.com 52 road science | continued Photo: Tom Kuennen Extraction of raw reclaimed asphalt pavement; modern cold milling machines lower cost of RAP production via higher productivity.