The rubber from recycled tires lends itself to a variety of applications ranging from asphalt to septic tanks. A California steel maker is even recycling the steel belted chord from the tires. Before recycled rubber and steel belting can be used regularly in these applications around the country, misgivings must be addressed and standards developed.
Cliff Ashcroft, vice president of FNF Construction, Fullerton, Calif., and member of the Rubber Pavements Association, Tempe, Ariz., said that “the potential is absolutely phenomenal” for tires used in asphalt paving. Ashcroft addressed attendees Spotlight on Rubber at the Institute for Recycling Industries Inc. (ISRI) Annual Convention in Las Vegas.
In addition to using 1,000 tires per lane mile, Ashcroft said that incorporating recycled crumb rubber into asphalt results in a superior product that is more cost effective in its design and that lasts longer. The antioxidants inherent in tires and their flexibility and resilience prevents strain from accumulating in the road surface, Ashcroft offered, which helps to reduce cracking.
Ashcroft explained that blending liquid asphalt with crumb rubber requires higher temperatures than the traditional method, ranging from 350 to 400 degrees. The process does not involve a number of modifications to existing machinery, Ashcroft said, though an adjustment is needed where the oil is incorporated.
The benefits of asphalt rubber include reduced thickness, cost savings, noise reduction, decreased cracking and improved long-term performance. Ashcroft explained that the asphalt rubber can be applied at half the thickness of traditional asphalt, which allows for quicker application at reduced cost.
Ashcroft said that an additional benefit of asphalt rubber is a 30 to 50 percent noise reduction.
Clifton Roberts, formerly an environmentalist with the South Carolina Department of Health and Environmental Control, also addressed the attendees. He pointed out that tire chips have to be cheaper and just as good, if not better, than the aggregate they’re replacing. Roberts said in coastal areas, tire chips represent a 50 percent savings when compared to aggregate.
Clearly, tire chips come in as the cheaper commodity, but do they perform better?
Roberts said that 1,000 septic tank installations are done each year n Hurry County, S.C., which has a population of 220,000. Each installation uses 1,000 tires. The county has discovered that tire chips provide a variety of advantages other than cost.
Trucks transporting the tire chips do not have to worry about weight limits, as the tires chips weigh roughly 80 percent less than the equivalent volume of aggregate. The void space in the septic tanks measures 62 percent with tire chips as compared to 44 percent with no. 5 stone, thereby increasing the water volume in the trenches and increasing the life of the septic tank, Roberts said. The tire chips also help to improve the system ecology, Roberts said, by increasing the quantity of protozoa and metazoa found in the system.
Despite these advantages, some drawbacks exist. Roberts said that consistent quality is an issue, as is regular availability. In addition, more cleanup is necessary when using tire chips in septic systems, whereas any stone that is strewn along the neighboring land does not need to be removed. Roberts also pointed out that the tire chips have to compete for public acceptance.
Leonard Robinson the environmental and safety manager for Tamco Steel, Rancho Cucamonga, Calif., knows something about battling perception. When he approached Tamco’s lab to ask if the steel belted chord from recycled tires could be used in the steel making process, he was told no.
“No means ‘not yet,’” Robinson said, and he set out to convince the lab that they could use the material.
Robinson said the steel belts provide many alloys. Currently, Tamco takes the chord for free, though he said if the chord could be supplied in briquettes of consistent quality, Tamco would value the material similarly to no. 1 scrap. Although an ISRI taskforce is currently working on developing standards for the material, challenges such as inconsistent density, rubber content, inconsistent quantity and bulkiness predominate.