The Asphalt Rubber Technology Service (ARTS) at Clemson University is striving to prove asphalt rubber's value and surmount the entrenched prejudices of conventional asphalt manufacturers and state highway officials.
This was the message of Serji Amirkhanian, director of ARTS and a civil engineering professor at Clemson, to attendees at the Clemson Tire Industry Conference held March 20-22 at Hilton Head.
The federal government's attempt several years ago to force states to use rubberized asphalt, through Section 1038 of the Intermodal Surface Transportation Efficiency Act, was an utter catastrophe that set the material's cause back 10 years, according to Mr. Amirkhanian.
``Contractors don't want to test anything new,'' he said. ``Asphalt rubber is going to cost you more, and that's enough to make it dead in the water. If it costs more, it's no good, and the officials who grant contracts don't look at the longer pavement life you get from asphalt rubber.''
ARTS is a partnership between Clemson's civil engineering department, the City of Clemson and the Office of Solid Waste Reduction and Recycling within the South Carolina Department of Health and Environmental Control. It has promoted the practical utilization of rubberized asphalt in South Carolina for more than 10 years, and its projects have made clear the superior life and performance of the material, Mr. Amirkhanian said.
One stretch of rubberized asphalt put down 10 years ago on Pelham Road in Clemson has developed no major problems, he said. The same is true of a portion of South Carolina state Route 24 that received asphalt rubber nine years ago.
The Pelham Road project used the ``dry process,'' in which approximately 3 percent of crumb rubber proportionately was added to the aggregate before the binder was added to the asphalt mix. About 18,000 scrap tires were used to pave that road, Mr. Amirkhanian said.
The SC 24 project used the ``wet process, in which 5 to 18 percent by binder weight of crumb rubber is added to the binder and mixed together before the addition of rocks. The crumb used in the wet process is finer than in the dry, he explained.
``We use crumb that is 99.99 percent steel-free and fiber-free,'' he said. ``It takes a little bit of money, but we're able to do it.'' ARTS usually prefers ambient to cryogenic crumb rubber for asphalt, he added, because cryogenic grinding gives the rubber a slightly glassy surface that doesn't allow as tight a bond with the asphalt as crumb ground at ambient temperatures.
For a technology that's been used in the U.S. since the early 1960s, a lot of myths still surround asphalt rubber, he said. One of these is that the fumes from asphalt rubber mixing operations are toxic to workers.
``Whenever I talk to contractors, the first thing they say is, `You're going to kill my people,''' he said. But studies performed in Europe, Canada and Florida have demonstrated there is no difference between rubberized and conventional asphalt in the kinds of fumes they produce.
ARTS sponsors at least 10 events per year allowing local and state agencies in South Carolina to meet with private firms for technology transfer and networking, Mr. Amirkhanian said. It designs and manages demonstration projects, and also provides interaction with other states and technology resources on asphalt rubber.
Perhaps its main activity, however, is its program to offer five-year grants and other monetary incentives to state and local agencies and contractors to persuade them to use asphalt rubber in various projects, he said.
Among the projects funded have been on Michelin Boulevard in Anderson County, S.C., and for the Pickens County, S.C., school district. Ford Motor Co. also has provided funds to help ARTS make grants for asphalt rubber playground surfacing, Mr. Amirkhanian said.