In recent years, due to increased construction costs, the use of recycled asphalt has become more widespread since it is becoming more cost-effective in many situations. In addition to having certain technical advantages, i.e., a pavement prone to low-temperature cracking or stripping will have less tendency to be so when it is recycled. 1977 saw increased use of drum-mixer plants to recycle hot-mix asphalt. This article focuses on three approaches to the problem of hot recycling of asphalt pavements within the requirements of the Federal Clean Air Act. In Kassuth County, Iowa, "a drum within a drum" process was used. Mineral aggregate was placed in the inner drum where the burner flame and heat were introduced while the asphalt pavement material was placed in the outer drum, thus preventing the burner flame from coming into contact with the salvaged asphalt pavement material-the main cause of blue smoke generation. At the discharge end of the inner drum, the asphalt and the aggregate are combined. In Fergus Falls, Minnesota, the asphalt was fed into the mixer by a conveyor belt through the mix discharge and of the drum while aggregate was fed into the burner end. Heat transfer from the latter to the former causes the asphalt to be heated without direct exposure to the burner, once again eliminating exhaust smoke. In Marion County, Oregon, a cylindrical combustion chamber with a conical heat shield at one end was installed between the burner and the drum entrance to prevent overheating the asphalt by controlling the heat transfer rate in the burner end of the drum. The flame volume is contained within the chamber where excess air and combustion gases are mixed to produce a lower temperature, air-rich mixture. The excess air flows into the combustion through slots in the chamber wall which provides wall cooling.

  • Corporate Authors:

    National Asphalt Pavement Association (NAPA)

    5100 Forbes Boulevard
    Lanham, Maryland  United States  20706
  • Authors:
    • Smith, R W
  • Publication Date: 1978

Media Info

  • Features: Figures; Photos;
  • Pagination: p. 5-9
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00179733
  • Record Type: Publication
  • Files: TRIS
  • Created Date: Oct 12 1978 12:00AM