The Maryland State Highway Administration has taken the lead in developing gap-graded Superpave mixes, which are stone matrix asphalt (SMA) mixes designed with Superpave performance-graded asphalts, fiber filler, and Superpave testing equipment, including the gyratory compactor. The mix offers so much promise in providing extremely durable pavements that industry stakeholders are urging that these gap-graded Superpave mixes be considered elsewhere. Alaska has sent four groups of investigators to Maryland to view gap-graded Superpave. In Maryland's Blue Ridge Mountains, the gap-graded mixes are resisting freeze/thaw cycles as well as heavy truck traffic. SMA is a high-performance, premium mix design that resists rutting and provides a noise-attentuating surface with reduced spray. SMA is especially appropriate for high-volume, high-loading routes. SMA features stone-on-stone contact that provides a load-bearing structural matrix and use of either modifiers and/or fiber additives to prevent drainage of liquid asphalt from the gaps between the stone. SMA mixes cost 20-25% more than conventional dense-graded mixes, but they more than make up for it in terms of reduced rutting and increased durability. Sidebars discuss the Baltimore Beltway's use of gap-graded Superpave mixes and outline how Maryland's use of gap-graded Superpave continues the collaborative development and advancement of SMA mixes in the United States.

  • Authors:
    • Kuennen, T
  • Publication Date: 1999


  • English

Media Info

  • Features: Figures; Photos;
  • Pagination: p. 12-18
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00768819
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Sep 11 1999 12:00AM