Controlling performance of crumb rubber-modified binders through addition of polymer modifiers

The use of tire rubber as a modifier to enhance the properties of asphalt mixes through the wet process has proved to be a successful procedure, but full control of the properties of crumb rubber-modified binders has been a challenge. The literature indicates a wide variation on adding rubber to asphalt and that the degree of success-of rubber modification in AC mixes depends on several factors, the majority of which relate to the method of mixing, storing, and transporting and to construction technologies. Understanding the nature of the interaction process between asphalt cement and crumb rubber-modifier (CRM) helps explain the development of binder properties. This paper covers the wet process, a relatively different technology in the application of CRM in asphalt with virgin polymers used to control and enhance the performance properties of CRM binders. The paper provides some clear insights into the mechanisms by which the interaction, with and without the existence of polymer modifiers, takes place. Effects of the interaction process variables, time and temperature, are explained. Results of this research are based on monitoring the changes in the rheological parameters of the developed binder.