In recent years, modified asphalt mixtures have become increasingly popular in the construction of flexible pavements. These products have gained popularity because of their ability to increase resistance to rutting at warm temperatures while reducing the occurrence of thermal cracking at cold temperatures. This, coupled with the growing problem of waste rubber tires, has led to the reprocessing (grounding) of tire rubber for use in asphalt concrete mixtures. In orderto investigate the warm temperature rutting hypothesis, a laboratory research program using both static and repeated load permanent deformation tests, carried out at two temperatures (77 degrees F and 104 degrees F), was designed to assess the potential benefits of rubberized asphalt concrete mixtures. Conclusions from this research indicated that the addition of ground tire rubber to asphalt concrete mixtures results in mixtures that exhibit less permanent deformation at high temperatures compared with unmodified mixtures. The research also indicated that permanent deformation testing should be carried out at high temperatures under repeated loading. The relative ranking of strain changes from 77 degrees F to 104 degrees F for both methods of testing and static testing indicates the presence of rubber; however, it does not indicate anything about the base asphalt. The repeated load testing indicates, in a reliable way, the differences that exist between binders.
Abstract