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CONSTRUCTION AND TESTING OF CRUMB RUBBER MODIFIED HOT MIX ASPHALT PAVEMENT

This research project was structured toward addressing that portion of the Intermodal Surface Transportation Efficiency Act (ISTEA) which directs the individual states to conduct studies on the recyclability of crumb rubber modified (CRM) hot mix asphalt (HMA) and the technical performance of CRMHMA pavement. These objectives were addressed by monitoring the construction of highway test sections in which CRMHMA was incorporated into the pavement structure, evaluating the performance of these sections and then cold milling and recycling this pavement material into new HMA through a HMA plant. This project was constructed in two phases in which the CRMHMA pavement was built in the first phase and approximately two years later milled and used as reclaimed asphalt pavement (RAP) in the surface course during the second phase. This report covers both phases of the construction. Three test sections were constructed in the westbound lanes of Federal Aid Project No. NH-007-1(53) on US 72 in Alcorn County. This project involved the paving of two new lanes that carried the westbound traffic of this route. The new lanes were paved and then placed under two-way traffic while old bridges were replaced on the old lanes. When the bridge construction was completed and the new lanes were carrying only westbound traffic, the surface course containing CRMHMA was milled and RAP was placed on the test sections. Primary conclusions and recommendations resulting from this study include the following: (1) During laboratory testing for the CRMHMA mix design, it was determined that the mixing temperature should be within the range of 351 to 390 deg F. (2) The CRMHMA was successfully produced in a normal HMA production facility with the addition of a blending unit being the only modification to the HMA production process. (3) Some additional air pollution was visually observed when the CRM was mixed with the asphalt cement (AC) in the portable blending unit and during plant operation for the production of the CRMHMA. (4) Review existing procedures and/or develop new procedures to mix the CRM with the AC at the terminal, deliver the blend to the HMA plant and maintain the blend at the HMA plant. (5) Placement of the CRMHMA on the roadway appeared to be in a normal fashion as it would be for regular HMA, except for increased smoke due to the higher temperatures required for compaction of the stiffer mix. (6) Laboratory tests conducted during the phase one construction displayed a difficulty in achieving the design air voids at the design AC content for the CRMHMA. (7) Some gumming of the various components of the plant including the coating unit through to the surge bins was observed due to the use of the rubber modifier in the mix. This did not pose a significant problem regarding plant operations for the production of the HMA for this study. (8) Initial performance tests were conducted on the CRMHMA pavement soon after completion of phase one construction. The pavement had low roughness readings and high skid values indicating that it was in an excellent initial condition.

Language

  • English

Media Info

  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 127 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00929216
  • Record Type: Publication
  • Report/Paper Numbers: FHWA/MS-DOT-RD-99-115,, Final Report
  • Files: NTL, TRIS, USDOT, STATEDOT
  • Created Date: Aug 16 2002 12:00AM