The effect of confinement on dynamic creep results

In a previous study the deformation resistance of a number of asphalt mixes was determined using the Accelerated Loading Facility (ALF). ALF loading (simulating traffic loading) ranked mixes with different aggregate grading in a different order to the dynamic creep test. Further work suggested that the lack of correlation of the creep test with field performance might be due to lack of confinement of specimens during testing. A limited study was undertaken to examine the feasibility of using two methods of specimen confinement during dynamic creep testing. The two methods were: (i) testing 150 mm diameter specimens using a 75 mm upper loading platen, and (ii) triaxial cell testing. The first method involved the use of an annulus of asphalt as a passive restraint, and the second method a triaxial cell with pulsed confining pressure to provide active restraint. Samples tested using the annulus restraint procedure showed the same ranking as the normal creep test and samples failed by "bursting". This method was not recommended for further study. The data for the triaxial cell procedure suggested there might be a reversal in the ranking of C2 and C1, compared to the standard creep test (ie, the results now agreed with ALF) but there was a wide scatter in results. No firm conclusion could be drawn on the ranking of the two mixes from such a small and imprecise data set although the results did suggest that the triaxial cell concept should be pursued. Because of equipment complexity, and extra testing time involved when providing a pulsed confining pressure, it was recommended that the use of a constant confining pressure be investigated. This could be provided fairly simply by means of an air pressurised diaphragm around the sample.

Language

  • English

Media Info

  • Pagination: 5.1-11
  • Serial:
    • Issue Number: 12

Subject/Index Terms

Filing Info

  • Accession Number: 01435609
  • Record Type: Publication
  • Source Agency: ARRB
  • ISBN: 086910683X
  • Files: ATRI
  • Created Date: Aug 24 2012 7:07PM