Control over Strain in the Dynamic Modulus Test

Bituminous mixtures exhibit complex visco-plasto-elastic behavior. However, implementation of purely linear viscoelastic properties at this early stage in the implementation of mechanistic-based models used in the analysis of flexible pavements is a reasonable starting point. This simplifying assumption requires that testing of asphalt concrete be performed at low strain amplitudes where the material response remains linear visco-elastic. The material testing system included in the NCHRP 1- 37A project adopted the dynamic modulus as the input to the M-E model that accounts for HMA stiffness, a property necessary for performing structural analysis to determine the state of stresses and strains in the asphalt concrete layer. The model uses the established state of stresses and strains to predict rutting and fatigue using performance models incorporated in the software. The current dynamic modulus testing approach is based on AASHTO standard test specifications designated TP62-03. This paper examined the response of a variety of HMA mixes using an alternative dynamic modulus testing technique based on controlling the strain in order to make sure that the linear viscoelastic assumption is truly being respected under the proposed stress-controlled testing technique. Results obtained using the strain-controlled testing technique suggest that the levels of stress proposed under TP62-03 are relatively high and may load the material beyond the viscoelastic response leading to the accumulation of permanent deformations. The strain-controlled testing approach seems to offer a more practical and reliable technique for determining the dynamic modulus of asphalt concrete mixes needed as input to the new M-E design model.

Language

  • English

Media Info

  • Media Type: CD-ROM
  • Features: Figures; References; Tables;
  • Pagination: 24p
  • Monograph Title: TRB 86th Annual Meeting Compendium of Papers CD-ROM

Subject/Index Terms

Filing Info

  • Accession Number: 01044216
  • Record Type: Publication
  • Report/Paper Numbers: 07-2307
  • Files: TRIS, TRB
  • Created Date: Feb 8 2007 7:00PM