EXTENT OF TOP-DOWN CRACKING IN COLORADO

In 2000, a forensic evaluation was conducted on a project that was exhibiting early longitudinal cracking near the wheel paths. A team of national asphalt experts conducted this forensic evaluation. The forensic team concluded that the cracking on the project was surface initiated cracking and was caused by a number of contributing factors. One of the contributing factors to the early distress that was identified by the experts were the pockets of segregation that were observed at the bottom of the surface lift but were not apparent on the surface. The object of this study was to determine the extent of "top-down cracking" in Colorado, what causes it, how can it be prevented, if it occurs how is the distress treated, and how quickly does the distress need to be treated. Out of the twenty-five sites that were cored 72% contained top-down related cracking. Of these 18 sites 67 had visual evidence of segregation. In 2003, a new mix design change was incorporated. The mix design change allows for an increase in the asphalt cement content, which will ultimately reduce the potential for segregation to occur. The Colorado Department of Transportation, in cooperation with industry, has established a segregation task force to develop a specification for segregation. This task force will be developing the specification to identify sub-surface segregation. Paving equipment manufacturers have also identified areas within the paver that promote segregation. The manufacturers have taken the initiative to develop an anti-segregation kit.

Language

  • English

Media Info

  • Features: Appendices; Figures; References; Tables;
  • Pagination: 53 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00961945
  • Record Type: Publication
  • Report/Paper Numbers: CDOT-DTD-R-2003-7
  • Files: TRIS, USDOT, STATEDOT
  • Created Date: Aug 18 2003 12:00AM