The Elk County Research Project in Pennsylvania consists of six test pavements constructed in September 1976 by using AC-20 asphalt cements from different sources. Two test pavements developed extensive low-temperature non-load-associated cracking during the first severe winter. After 2.5 years in service and two more severe winters, the remaining four test pavements do not exhibit any significant cracking. Periodic performance evaluation of these pavements has been conducted. Cracking of the two test pavements was attributed to high stiffness moduli of asphalt cement and asphaltic concrete, determined by indirect nomograph methods. It was felt that the stiffness moduli should also be determined by direct measurements on actual pavement cores. Split tensile tests were conducted at four below-freezing temperatures at a deformation rate of 1.27 mm/s (0.05 in/min) to determine such basic mix properties as stiffness modulus, tensile strength, and tensile strain at failure. Stiffness moduli of the aged pavements were also determined by the indirect Heukelom and McLeod methods. The data from the tensile test indicate that tensile strength or tensile strain at failure, considered independently, does not explain the low-temperature cracking phenomenon on this project. Both direct measurements and indirect methods show that the stiffness modulus of the asphaltic concrete is a better indicator of potential low-temperature cracking. Stiffness moduli determined from the tensile test were generally found to be lower than those obtained by the two indirect methods. A maximum permissible stiffness modulus of 26.9 MPa (3900 lbf/sq in) for original asphalt cement (at minimum pavement design temperature and 20,000s loading time) has been selected to develop AC-20 asphalt cement specifications for the cold regions of Pennsylvania. (Author)

Media Info

  • Media Type: Print
  • Features: Figures; References; Tables;
  • Pagination: pp 39-50
  • Monograph Title: Asphalt: materials, mixes and construction
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00334210
  • Record Type: Publication
  • Files: TRIS, TRB
  • Created Date: Sep 16 1981 12:00AM