Binder hardening in ALF asphalt deformation trial samples

In the ALF asphalt deformation "core" trial, differences in properties were observed between specimens cored from the pavement and specimens of plant mix of the same composition compacted using a Gyropac. In an effort to understand the reasons for this, asphalt was sampled during various stages of manufacture of the phase two ALF deformation trial sections, and at various stages of the laboratory conditioning and compaction process. Binder was recovered from the samples by a solvent extraction procedure and its viscosity measured. This allowed the hardening which occurred at each stage of the field and laboratory processes to be calculated. It was found that laboratory mixing produced a similar degree of binder hardening to plant (pugmill) mixing. The overall laboratory mixing and conditioning process hardened the binder more than the comparable field situation. This was because minimal binder hardening occurred during transportation to the ALF site. The RTFO procedure produced similar hardening to plant mixing, and also (because of the minimal hardening of the field mix during transportation) to the total binder hardening during the mixing and laying process. The agreement between duplicate specimens was generally good with the exception of the conditioned, Gyropac specimens compacted at the mixing plant. These recorded values of 1.48 and 1.78 MPa.s, indicating that further investigation may be necessary. The viscosity of binder recovered from specimens cored from the pavement was 0.41 MPa.s less than the viscosity of binder recovered from laboratory compacted specimens. This result is in agreement with testing carried out earlier on phase one specimens and suggests that the observed difference in modulus and creep between the ALF pavement and Gyropac compacted specimens may be attributable, at least in part, to differences in the binder viscosity of the specimens. A more extensive sampling and testing exercise would be required to determine the precision of the reported results. Comparison of bitumen hardening during mix manufacture and placement (short-term hardening) with hardening during field service (long-term hardening) indicated the greatest proportion of bitumen hardening occurs as a result of the long-term process. The AUSTROADS conditioning procedure appears to produce binder hardening equivalent to about one year of service in the field. The study was funded by the Australian Asphalt Pavement Association (AAPA) as part of its continuing program of research undertaken to improve asphalt performance.

Language

  • English

Media Info

  • Pagination: 8.1-8
  • Serial:
    • Issue Number: 12

Subject/Index Terms

Filing Info

  • Accession Number: 01435612
  • Record Type: Publication
  • Source Agency: ARRB
  • ISBN: 086910683X
  • Files: ATRI
  • Created Date: Aug 24 2012 7:07PM