Continuous and Quick. Hot In-Place Recycling
Hot in-place recycling is a continuous process performed with a self-contained train of equipment. Approximately 1 to 1½ inch of the existing pavement surface is heated, scarified, treated with rejuvenating emulsion, milled, mixed, replaced on the road with a vibratory screed and compacted. A surface course or treatment may be applied immediately after the recycling. Or, if it is a better fit for construction scheduling, the surface may be applied later. During hot in-place recycling, only the lane being recycled is closed, and it can be reopened quickly after the compaction is completed.
Pavement Preparation. Hot in-place recycling should only be done on structurally sound pavements with good base structures. Prior to recycling, any structural problems in the base should be repaired, and the existing pavement should be swept of deleterious materials.
Heating. Heaters are used to elevate the temperature of the pavement to approximately 300°F. The heating softens the surface.
Scarifying. The softened pavement is scarified to break apart the surface and prepare it for the application of the rejuvenator emulsion.
Applying the Encore™ Emulsion. The EncoreTM rejuvenating emulsion is metered and applied at a predetermined rate using a system calibrated for the correct shot rate. Testing done in a SemMaterials laboratory determines the optimal amount of emulsion for each hot in-place recycling project. The safe, water-based emulsion is formulated specifically for the hot in-place recycling process. The rejuvenating oils in the emulsion replace the chemical constituents of the asphalt that have oxidized and aged over time. The Encore emulsion also contains SemMaterials Stylink® polymer modified asphalt, which further improves the elasticity, coating, moisture resistance, rutting resistance and cracking resistance of the recycled pavement. The result is a durable mix for a longer lasting pavement.
Milling and Mixing. The rejuvenator treated surface is milled with a milling head and mixed with an on-ground pugmill to coat the milled material. The result is a black, completely coated mix.
Paving. The rejuvenated mixture is placed with a paver using a vibratory screed, resulting in a smooth surface with a corrected profile.
Compacting. The newly recycled pavement is immediately compacted with conventional rollers and is ready for traffic return or for a surface treatment.
A Cost-effective, Environmentally-friendly Solution
Aged, distressed pavements are replaced with smooth, durable surfaces.
- Deformations such as potholes, ruts, bumps and shoved pavement are leveled.
- Cracked pavement is removed.
- Crowns are re-established.
- Clearances under bridges and curb height are retained.
Recycling reuses existing aggregate & asphalt, reducing new raw material & hauling costs.
- There is excellent public acceptance of recycled materials.
- RAP (reclaimed asphalt pavement) is a valuable raw material instead of being relegated to unsightly waste piles.
- The recycled pavement can, itself, be recycled when its time has come.
The recycled pavement can be higher quality than the original.
- The rejuvenator oils restore the chemical composition of the oxidized, aged asphalt.
- The process completely coats the aggregate.
- The Stylink® polymer modified asphalt improves durability, flexibility, adhesion, strength and resistance to temperature extremes, rutting and cracking.
- EncoreTM mixes have shown 35% higher strengths than recycled mixes made with conventional, off the shelf emulsions.
In-Place recycling minimizes the time a lane is closed for reconstruction and lowers user delay costs.
Project Selection and Design
There have been successful recycling projects on rural roads, busy city intersections and Interstate highways. In selecting hot in-place recycling for a particular project, it is important to understand the pavement structure and causes for distress. We don’t want to make the same mistakes which caused premature distresses—such as using stripping sensitive materials or sub-base problems. Since hot in-place recycling removes and rejuvenates the top portion of the pavement, the pavement structure and base should be sound, and there should be adequate drainage.
The existing asphalt concrete should be tested. The EncoreTM additive design depends upon the asphalt content, the physical properties of the extracted asphalt, and the quality and gradation of the aggregate. With the correct mix design, the new pavement will be cost-effective, smooth and durable.