Hot In-Place Recycling

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Application Sequence

1. Preheaters dry, heat and soften existing pavement

2. Heater Scarification unit applies final heating and scarifies/loosens softened pavement to the required depth

3. Heater Scarification unit applies rejuvenating agent to loosened material (Surface Recycling and Repaving only)

4. For Remixing, loosened material, rejuvenating agent and any new aggregate or HMA is mixed in a mixing unit or pugmill

5. For Surface Recycling & Remixing, the recycled material is deposited in a paver and placed to the required grade, depth and cross-slope

6. For Repaving, the recycled mix and new HMA are placed simultaneously to the required grade, depth and cross-slope

7. The recycled mix is compacted to the required density using rubber-tired and/or steel wheel rollers

8. Allow traffic on the recycled mix after final rolling and as soon as the layer can support the traffic without damage

9. A new wearing surface is placed (Surface Recycle and Remix only)


Application Guidelines

Control Strip

• If required, a control strip should be placed at the beginning of the project to evaluate the equipment, construction methodology, workmanship and to verify that the construction process meets specification requirements  

Pavement and Mixture Heating

• Check pavement and mixture temperatures between preheater and heater/scarification units and at the back of the screed

• Maximum preheating temperatures should generally not exceed 375 °F (190 °C)

• The average temperature of the loosened recycled asphalt mixture should be 230 to 300 °F (110 to 150 °C)

• The average temperature of the underlying layer should typically be 120 to 180 °F (50 to 80 °C) to allow a thermal bond with the recycled mix

• For adequate compaction, the temperature of the recycled layer should typically be between 190 to 265 °F (88 to 130 °C)

Temperature monitoring should take place between all preheaters to ensure proper heating prior to recycling.

Scarification/Milling Depth

• Check scarification or milling depth behind each heater/scarification/milling unit

Recycled Mixture

• The recycled mixture should look uniform with no major segregation, streaks or fat/oily spots

• The recycled mixture should be placed to a consistent depth, width and cross-slope

• Check for cross-slope and width directly behind the paver


• Establish a rolling pattern to achieve the required percent compaction

• Compaction requirements are typically the same as local agency HMA specifications

• Compaction procedures are the same as for HMA

• Check compaction with a gauge or by cutting cores after the mat has cooled

• Check cross-slope after final rolling 

Return to Traffic

  • Traffic can be returned to the recycled mat as soon after final rolling as long as it can support the traffic without damaging the recycled layer.