TEMPERATURE CORRECTION OF ASPHALT-MODULI FOR FWD-MEASUREMENTS

An important factor in the evaluation of exiting pavements is to determine the bearing capacity characterized by the Elasticity Modulus (E-modulus) of each layer in the structure. Often this is done routinely, through backcalculation of deflection basins measured by a Falling Weight Deflectometer (FWD). During the FWD measurement, the temperature of the asphalt layer has to be recorded, as the asphalt stiffness is strongly influenced by temeprature. On the basis of the temperature, the calculated asphalt modulus can be corrected to a modulus at a reference temperature. The asphalt temperature is currently found in Denmark by measuring at a depth of 40mm below the surface. Of the procedures known today, we still believe that the best way to determine temperature is to drill a hole in the AC-layer and measure with a thermometer. But the optimum depth at which to measure is relative, depending on the thickness of the asphalt layer. To find the optimum depth and the relationship between temperature and E-modulus at that depth, field tests have been carried out, measuring deflections and temperature gradients simultaneously. These tests were conducted over a 24-hour period in order to take both heating and cooling of the asphalt layer into account, leaving out the interference from change in moisture content of the subgrade and subbase. This paper presents the results of these tests, giving an evaluation of an optimum depth at which the asphalt temperature should be measured, along with a programmable formula for correcting the calculated asphalt-moduli. Also, the AASHTO temperature correction procedure is tested on the field data and discussed.

Language

  • English

Media Info

  • Features: Figures; Tables;
  • Pagination: p. 753-768
  • Serial:
    • Volume: 1

Subject/Index Terms

Filing Info

  • Accession Number: 00730087
  • Record Type: Publication
  • Files: TRIS, STATEDOT
  • Created Date: Nov 27 1997 12:00AM