Ultrathin layer Asphalt workshops

1
Ultra-thin layer Asphalt workshops

• May 2002

2
Scope of workshops

• To discuss concerns with UTLAs. Initially defined
  as lt25 mm (but consideration should be given to
  thicknesses of up to 30 mm)
• Provide solutions to address the concerns
• Two workshops
• Suppliers/contractors
• Clients/consultants

3
Conclusions

• Performance expectations and design parameters
  for UTLAs vary widely
• 4 different types were identified
• Conventional asphalt (lt30mm)
• Stone Mastic Asphalt
• Thin layer performance asphalt
• Residential asphalt
• Confusion about the different types of UTLAs

4
Main Concerns

• Compaction
• Inexperience with the use of UTLAs
• Inappropriate pavement designs
• Inappropriate mix designs
• Inappropriate specifications

5
New findings

• Widespread confusion about the different types of
  UTLAs
• The extent of engineering compromise which occurs
  in some applications
• The problems with rapid cooling in all seasons in
  SA
• The need to provide for inexperienced supervisors
  and designers in the future

6
Suggested actions

• To redefine UTLA as various asphalt gradings
  with a layer thickness of 30mm or less
• Develop new guidelines covering the identified
  needs of basic construction supervision and a
  generic functional layer (in residential areas)
• Thin layer performance asphalts were deemed to be
  proprietary products and outside the scope of
  such a guideline

7
Area for consideration