Hot-in-place® recycling (HIP®AR) has been evolving for more than 50 years. Green Roads Recycling® uses a “two-step process” that recycles 100% of the existing asphalt to a depth of 50 millimetres (≈2 inches).
This is Accomplished by:
- Heating the existing road to soften it, which makes it possible to remove two layers of asphalt
- Mechanically combining those two layers and mixing in a rejuventating agent and/or additional new asphalt
- Laying the newly-mixed asphalt down to create the new road surface
In other words, HIPAR® recycles all the existing oil and aggregate in the road and lays it down in one fluid motion to a like-new condition.
Operating Parameters
- Deteriorated asphalt pavement.
- Pavement section heated by infra-red heaters prior to milling.
- Floating milling heads remove outermost third of highway lane to a depth of 25mm.
- Hot milled material is windrowed into centre lane.
- A milling head, at the front of the B unit, mills to another 25mm.
- If specified, virgin mix or asphalt rejuvenates, may be applied at this point.
- Newly exposed surface is heated across full lane width.
- Full width mandrel, mills heated surface to a depth of 25 to 35mm. All material is augered into centre lane.
- The material is thoroughly mixed and elevated into a twin shaft pugmill and then into the paver hopper.
- A new mat 50mm deep is laid by conventional screed. The original elevation will be achieved after rolling.
Specification
- Mixed material immediately behind screed is maintained at approximately 110 degrees
- Production capability — 7000-11,000 sq. m/day, which is equivalent to a finished, reconstituted highway of 3-lane kilometers or 1.85 miles
HIP PROJECTS CRITERION
- Wheel path rutting — less than 50 mm
- Patching- low to medium frequency
- Wheel path fatigue cracking — low severity
- Transverse cracking — we do projects with lots of transvers cracking and like mill and fill projects they come back over time.
- Bleeding — bleeding pavements are considered
- Existing pavement thickness — minimum 50 mm to 100 mm. Although we have done roads with an asphalt depth of only 50mm and recycled the top 40mm, the projects were still considered to be very successful.
- Roughness — smooth to moderate. We have done rough roads and it was made way better
- Structural condition — minimum structural capacity based on strength testing
- Projects with extensive rubberized crack sealant or high percentages of rubber tires may not be considered. However we do major crack sealing very often.
- Bottom lifts then overlaid for structural strength with hot mix
- Chip sealed or seal coated is okay
- Four inch rehabilation – two inch hot-in-place plus two inch overlay
