Grantee Research Project Results
Final Report: A Novel Method for Converting a Negative Value Waste Into a Commodity Chemical
EPA Contract Number: 68D00248Title: A Novel Method for Converting a Negative Value Waste Into a Commodity Chemical
Investigators: Denvir, Adrian J.
Small Business: Lynntech Inc.
EPA Contact:
Phase: I
Project Period: September 1, 2000 through March 1, 2001
Project Amount: $70,000
RFA: Small Business Innovation Research (SBIR) - Phase I (2000) RFA Text | Recipients Lists
Research Category: Hazardous Waste/Remediation , SBIR - Waste , Small Business Innovation Research (SBIR)
Description:
The purpose of this Phase I Final Report is to summarize the results of studies on the feasibility of using ozone gas to modify the surface of crumb rubber so that when it is blended into asphalt, it improves the overall quality of the asphalt binder. With approximately 300 million tires discarded in the United States each year, the rapidly growing accumulation of scrap tires exists chiefly because there is a lack of markets for scrap tires or scrap tire products.Rubber modifiers have been used in bituminous materials since the 1840s, and there has been much research to indicate that crumb rubber can improve certain characteristics of asphalt pavements. The obvious benefit of adding rubber to asphalt is that the rubber imparts elasticity to the binder, which helps the pavement fatigue and resistance, as well as reducing reflective cracking. The increased flexibility decreases the pavement's susceptibility to low-temperature cracking. Rubber-modified pavements have been shown to improve skid resistance even under ice conditions. Crumb rubber also has been found to increase the tensile strength, toughness, ductility, and thus durability of the pavement.
One of the primary problems with the conventional crumb rubber-modified asphalt binder is that it has poor settling qualities; the crumb rubber particles tend to settle to the bottom of the holding tank before they can be mixed with the aggregate. Another problem is that the crumb rubber particles do not disperse evenly through the asphalt, which results in raveling after only a limited amount of use. It has been found that the quality of the asphalt after the addition of the crumb rubber is a function of the amount of interaction between the asphalt and the crumb rubber particles. Presently, this interaction is achieved by mixing the crumb rubber and asphalt at elevated temperatures and high shear conditions. There are, however, problems associated with this technology. High temperatures and high shear forces in the process have raised environmental concerns.
Summary/Accomplishments (Outputs/Outcomes):
These studies have demonstrated that ozone gas can be used as a cost-effective treatment to chemically modify the surface of the crumb-rubber particles, allowing them to chemically bond to the asphalt. The ozone treatment also partially devulcanizes, allowing the particles to break down into smaller pieces during the curing process. Analysis has shown the asphalt binder generated using the ozone-treated crumb rubber has improved settling characteristics and high-temperature viscosity properties. The ozone treated crumb rubber-modified asphalt binder also has excellent low temperature properties that would pass inspection from both southern and northern states.Conclusions:
The ease with which the ozone treated material has to incorporate itself into the asphalt has the potential to significantly reduce processing costs. Discussions with end users and crumb rubber manufacturers have identified this technology as having great commercial potential as it fulfills a niche area in the market.Supplemental Keywords:
solid waste, recycling, engineering, chemistry., RFA, Scientific Discipline, Air, Waste, Chemical Engineering, Municipal, Environmental Chemistry, Hazardous Waste, Chemistry and Materials Science, Engineering, Chemistry, & Physics, Hazardous, Environmental Engineering, tires, recycled waste products, municipal solid waste landfills, recycling, crumb rubber, treatment, solid waste, reuse, waste recoveryThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.