Evaluation of 4.75-mm Superpave Mixture

Superpave asphalt mixture with 4.75-mm nominal maximum aggregate size (NMAS) is a promising, low-cost hot-mix asphalt mixture. This mix, when applied as a thin layer, has the potential to provide a very smooth riding surface and correct surface defects for low- to medium-volume facilities. The main objective of this research study was to examine the volumetric properties and to evaluate performance of 4.75-mm NMAS mixes in the laboratory considering three factors: aggregate source, natural sand content and binder grade. Two rehabilitation projects were done in Kansas in 2007 using 4.75-mm NMAS superpave mixture overlay. Twelve different 4.75-mm NMAS mix designs were developed in the laboratory using materials from these projects along with two binder grades and three different percentages of natural (river) sand. Test results show that design binder content is relatively high for these fine mixes. The effective asphalt content in the design mix is highly influenced by the natural sand content. Mixture density at the initial number of gyrations and dust-to-binder ratio are also influenced by natural sand content. Rutting performance of such mixes during Hamburg Wheel Tracking Device tests is aggregate source specific. Higher binder grade may or may not improve rutting performance of 4.75-mm NMAS mixes. Anti-stripping agent affects the moisture sensitivity test results irrespective of aggregate source, natural sand content and binder grade. Dust-to-binder ratio is the most significant mixture parameter that affects mix performance. An optimized 4.75-mm NMAS mixture may have a much narrower range of the dust-to-binder ratio than that is allowed in the current specifications. Further study is recommended in this matter.


  • English

Media Info

  • Media Type: DVD
  • Features: Figures; Maps; Photos; References; Tables;
  • Pagination: 18p
  • Monograph Title: TRB 89th Annual Meeting Compendium of Papers DVD

Subject/Index Terms

Filing Info

  • Accession Number: 01158062
  • Record Type: Publication
  • Report/Paper Numbers: 10-2608
  • Files: TRIS, TRB
  • Created Date: May 30 2010 7:44AM