HILTON HEAD, S.C.—Dry process crumb rubber modified asphalt (CRM) is the way forward if rubberized asphalt is to be a viable recycling technology in the future, according to a speaker at the 34th Clemson University Global Tire Conference.
"The window of opportunity is open, but it won't remain open, because more aggressive industries will beat us to it," Redmond Clark, president of Asphalt Plus L.L.C., said at the conference held April 18-20 at Hilton Head, S.C.
With more than 50 percent of all recycled rubber being used in non-sustainable markets, CRM using crumb rubber from recycled tires seems like a natural choice for all stakeholders, according to Clark.
Over the years, CRM has proved to last longer than regular asphalt. Clark said it provides a quieter pavement, better traction, lower maintenance and a great return on investment.
"Asphalt could consume all recycled tire rubber globally," Clark said. Potential U.S. demand for recycled crumb rubber in the asphalt industry is about 6 billion pounds annually, which is the same amount U.S. waste tire operations could generate annually.
Nevertheless, only about 120 million pounds of recycled rubber is used for CRM every year—2 percent of the market potential.
Clark said there are multiple reasons for this. CRM has never really lived down the debacle of the Intermodal Surface Transportation Efficiency Act in the early 1990s.
ISTEA required state highway agencies to use an increasing percentage of CRM in highway projects as a prerequisite of receiving federal highway funds. However, states tried pilot projects without really understanding the technology, and the results were so disastrous that highway officials rebelled.
The rubberized asphalt provisions of ISTEA were repealed after a few years. "Rubber has been burned with a black mark ever since," Clark said.
The "terminal blend" CRM technology from ISTEA days remains unpopular with customers, according to Clark.
"The mix sticks to their equipment, and they have trouble keeping the rubber particles suspended because they can't melt," he said.
Meanwhile, tire industry suppliers are selling styrene-butadiene-styrene polymers for use in hot-mix asphalt, and SBS has become much more popular than CRM, according to Clark. SBS is less expensive than terminal blend CRM, performs as well in asphalt and melts easily in the mix.