The Effect of WMA on RAP in Hot Mix Asphalt

The use of warm mix asphalt (WMA) is becoming more popular in the asphalt industry. The promise of reduced energy consumption, reduced emissions, and a more workable product is very appealing to an industry pressured by environmentalists with sustainability agendas and state agencies applying pay adjustments based on ride quality and pavement density. However, the use of WMA may require the modification of current hot mix asphalt (HMA) mixture design procedures to ensure the WMA technologies are not detrimental to volumetric and performance criteria. Poorly dried aggregates may create issues of moisture damage with some water based WMA technologies, while other WMA technologies advertised as an anti-strip may actually improve the resistance to moisture damage. Reduced production temperature may also limit the amount of recycled asphalt pavement (RAP) asphalt binder transfer into the asphalt mixture, but at the same time aid at reducing the degradation of styrenebutadiene-styrene (SBS) polymer in polymer modified asphalt binders. In conjunction with these potential issues, recent research conducted during NCHRP Project 9-43, A Mix Design Procedure for Warm Mix Asphalt (WMA), suggests that WMA mixtures should be designed separately from hot mix asphalt. In an effort to answer some of these questions, a research effort was undertaken to evaluate the impact of WMA production and technologies on asphalt mixture design and performance. Gel Permeation Chromatography (GPC) testing suggests that the reduced production temperatures associated with WMA will help to limit polymer degradation when using polymer-modified asphalt binders. Some of the WMA additives improve the resistance to moisture damage, while other technologies provide no additional benefit to moisture damage resistance. Both Sasobit and Rediset demonstrated anti-strip ability, similar to that advertised by Evotherm. The laboratory WMA design process was found to reduce the optimum asphalt of the mixture when compared to the identical mixture design under hot mix asphalt conditions. This is most likely due to the increase in compactability the WMA technologies provide. Performance testing showed that WMA mixtures designed with 25% RAP met all permanent deformation and stripping requirements. A database of WMA and companion HMA projects produced in New Jersey have demonstrated that WMA performs as well as HMA.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Edition: Final Report
  • Features: Appendices; Figures; Photos; References; Tables;
  • Pagination: 81p

Subject/Index Terms

Filing Info

  • Accession Number: 01678159
  • Record Type: Publication
  • Report/Paper Numbers: FHWA-NJ-2015-009
  • Files: TRIS, ATRI, USDOT, STATEDOT
  • Created Date: Aug 10 2018 7:37AM