California Department of Transportation
 

Hot In-Place Recycling (HIPR)

Hot In-Place Recycling (HIPR) is an on-grade method of pavement surface preservation that consists of softening the existing asphalt pavement with heat, milling or scarifying to a maximum depth of 2 inches, and thoroughly remixing, leveling, and compacting the milled or scarified material. HIPR can include the addition of recycling agents and virgin hot mix asphalt (admix) as needed.


Smoothing Machine

Hot In Place Recycling Train

Application

HIPR is best suited for roadways with light truck traffic. HIPR can treat pavement distresses and surface irregularities including:
  • Raveling
  • Bleeding
  • Corrugations
  • Shoving
  • Slippage
  • Poor ride quality
  • Shallow rutting
  • Shallow potholes
  • Non-fatigue cracking (longitudinal, transverse, or reflection)

 

Limitations

HIPR should not be used on pavements with:

  • Multiple chip seals
  • Rubberized Hot Mix Asphalt (RHMA)
  • Geosynthetic Pavement Interlayer (GPI)
  • Structural inadequacy
  • Greater than 5% alligator cracking
  • Moderate to excessive filled cracks
  • Base or subgrade failure
  • Moisture related problems:
    • Poor drainage
    • Pumping
    • Saturated subgrade material

 

Please forward any questions/comments/suggestions to Waheed Maroof (waheed_maroof@dot.ca.gov). Last updated 09/16/2011.