For Pavement Condition
Hot In-place Recycling (HIR) is an on-site, in-place pavement preservation and corrective maintenance technique that when combined with an asphalt overlay can be classified as structural rehabilitation. There are three sub-disciplines of HIR; Surface Recycling, Remixing and Repaving. All HIR sub-disciplines consist of heating, softening, scarifying/hot milling, mixing, placing and compacting the existing pavement. Rejuvenating agents and additives can be integrated into HIR mixtures to improve the characteristics of the recycled pavement. HIR should be considered whenever mill and fill or a leveling course is required prior to an asphalt overlay.
- 20-40% more cost effective than conventional maintenance/rehabilitation techniques
- Reduces greenhouse gases by up to 30%
- Reuses 100% of existing materials
- Same day return to traffic
- Extends pavement life by 7-15 years (dependent on the ability to restore asphalt viscosity and mitigate any existing asphalt mixture deficiencies)
- Structural Layer (a) Coefficients between 0.42 and 0.44 (equivalent to agency values for HMA)
Issues Addressed
- Oxidation
- Uneven surface profile
- Top down cracking
- Minor rutting
- Raveling
- For a complete list, see Table 6-1 of the BARM
Attributes
- Rejuvenates oxidized asphalt binder restoring pavement flexibility
- Conserves non-renewable resources and reduces trucking
- Eliminates defects within the recycling depth
- Maintains curb reveal and overhead clearances
- Retards crack mitigation from underlying aged asphalt layers
Common Combinations
Surface Recycling and Remixing
- HIR + single or double chip seal
- HIR + Micro or Slurry Surfacing
- HIR + hot mix overlay
- HIR + ultra-thin bonded wearing course
- Occasionally used as a wearing surface for low volume roads
Repaving
- Places an integral asphalt overlay on top of the recycled layer in a single pass
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