Crumb Rubber Modifiers (CRM) in Asphalt Pavements: Summary of Practices in Arizona, California, and Florida

1995Bonaquist, RamonPDFTech ReportFHWA-SA-95-056DTFH61-94-C-00035Crumb rubberAsphalt pavementsPavement performanceThicknessMix designUnited StatesUnited States. Federal Highway Administration. Office of Technology ApplicationsHicks, R. G.Lundy, James R.Leahy, R. B.Hanson, D.Epps, Jon A.United States. Federal Highway Administration. Office of Technology ApplicationsOregon State University. Transportation Research InstituteBonaquist, RamonFederal Highway AdministrationHighway agencies have been evaluating crumb rubber modifier (CRM) in hot mix asphalt (HMA) since the 1970's. Three agencies, Arizona, California, and Florida, currently use CRM in HMA at levels that would approach or exceed the mandate in Section 1038 of the Intermodal Surface Transportation Efficiency Act of 1991. This report documents the use of CRM in HMA in these three States. In particular, it addresses issues including thickness design, materials and mix design, construction procedure, including quality control, and pavement performance. The report also addresses the following questions: (1) What processes are used? (2) Why are they used? (3) How are the products performing? Significant findings include the following: CRM-HMA is used primarily as a functional overlay. Functional overlays are used to improve ride quality and skid resistance or pavement deterioration. The wet process is used exclusively in the three States in dense-, gap-, and/or open-graded mixes. The agencies use modified versions of the Marshall or Hveem mix design procedures. Cost for CRM-HMA ranges from 15 to 70k percent higher than conventional HMA. All agencies feel they are obtaining added value with CRM-HMA. However, there are inadequate data to quantify the benefits. Form DOT F 1700.7 (8-72) Reproduction of completed page authorized This report is one of several to be developed as a part of this EXWA study titled "Crumb Rubber Modifiers in Asphalt Pavements."83