AASHTO Journal - Survey: Use of Warm-Mix Asphalt Keeps Climbing

An annual survey conducted by the National Asphalt Pavement Association in partnership with the Federal Highway Administration over the last nine years found that “warm-mix asphalt” made up nearly 39 percent of all asphalt pavement mixtures produced in the United States in 2017.

The survey – conducted in the first quarter of 2018 with 238 companies operating 1,158 plants in all 50 U.S. states, the District of Columbia, and American Samoa, along with data from state asphalt pavement associations for 32 states – also determined that more than 99 percent of the asphalt pavement material removed from roads and parking lots in 2017 was put back to productive use, primarily in new asphalt pavement mixtures.

Craig Parker, executive vice president of Silver Star Construction in Moore, Oklahoma, and NAPA’s chairman, noted in the report that warm-mix asphalt is made at “reduced temperatures,” which decreases energy demands, reduces air emissions, and improves compaction at cooler temperatures.

[Photo: VDOT]

The use of warm-mix asphalt had tracked at about a third of all asphalt mixture production since 2013, he pointed out, with the increase for 2017 attributable to an increase in the tons of warm-mix asphalt used by state departments of transportation.

“Companies that produce warm-mix asphalt reported that about 42 percent of the asphalt pavement mixture produced for DOTs was produced at reduced temperatures using warm-mix technologies,” Parker said. “During 2017, more than half of all asphalt pavement mixtures in 16 states were produced as warm-mix asphalt, and in eight of those states, more than 75 percent was produced as warm mix. Road owners are clearly seeing the benefits these technologies bring to our product, and they are willing to support innovations in asphalt pavements.”

Also, according to the survey, nearly 79 million tons of recycled materials — primarily reclaimed asphalt pavement material or “RAP” and recycled asphalt roofing shingles or “RAS” — were used in new asphalt pavement mixtures during the 2017 construction season, which was similar to the amount of these materials used in 2016. Ground tire rubber, steel and blast furnace slag, and recycled cellulose fibers were among the other recycled materials used in new asphalt pavements in 2017.

Overall, the use of RAP and RAS alone resulted in cost savings of more than $2.2 billion compared to the use of virgin materials, NAPA said.

The survey found that more than 76.2 million tons of RAP and nearly 950,000 tons of RAS got used in new asphalt pavement mixes nationally during 2017, with an additional 3.9 million tons of RAP and RAS were used as aggregate, in cold-mix asphalt, and other road-building activities.

The national poll also determined that at the end of 2017 about 103.5 million tons of RAP and RAS was stockpiled for future use across the country, with the reclaiming of RAP for use in future pavements saved nearly 50 million cubic yards of landfill space during 2017.

Although national usage estimates were not calculated, respondents to the survey reported recycling some 1.5 million tons of ground tire rubber, slags, cellulose fiber and other reclaimed and waste materials into nearly 7.5 million tons of asphalt paving mixtures.