# Cold In-Place Recycling Cold in-place recycling (CIR) is the processing and treatment with bituminous and/or chemical additives of existing HMA pavements without heating to produce a restored pavement layer (AASHTO, 1998). - Canonical URL: https://pavementinteractive.org/reference-desk/maintenance-and-rehabilitation/rehabilitation/cold-in-place-recycling/ - Last updated: 2026-11-01 - Review: reviewed by licensed professional engineers on the previous Pavement Interactive site, where reviewers were not recorded by name Cold in-place recycling (CIR) is the processing and treatment with bituminous and/or chemical additives of existing HMA pavements without heating to produce a restored pavement layer (AASHTO, 1998[^1]). It involves the same process of [cold plant mix recycling](https://pavementinteractive.org/reference-desk/pavement-types-and-history/pavement-types/cold-plant-mix-recycling/) except that it is done in-place by a train of equipment. ## Procedure The typical CIR process involves seven basic steps (AASHTO, 1998[^1]): 1. **Milling**. A [milling machine](https://pavementinteractive.org/reference-desk/construction/site-preparation/existing-surface-preparation-for-overlays/) pulverizes a thin surface layer of pavement, usually from 50 to 100 mm (2 to 4 inches) deep. 2. **Gradation control**. The pulverized material is further crushed and graded to produce the desired gradation and maximum particle size. On some jobs this step is omitted, however on others a trailer mounted screening and crushing plant is used to further crush and grade the pulverized pavement. If needed, virgin aggregate can be added to the recycled material. 3. **Additive incorporation**. The graded pulverized material is mixed with a binding additive (usually [emulsified asphalt](https://pavementinteractive.org/reference-desk/materials/asphalt/emulsified-asphalt/), lime, [portland cement](https://pavementinteractive.org/glossary/portland-cement/) or fly ash). On some jobs, this is done by the milling machine, however on others a trailer mounted pugmill mixer is used. 4. **Mixture placement**. The pulverized, graded pavement and additive combination is placed back over the previously milled pavement and graded to the final elevation. Mixture placement is most often done with a traditional [asphalt paver](https://pavementinteractive.org/reference-desk/construction/placement/asphalt-paver/) (either through [windrow pickup](https://pavementinteractive.org/reference-desk/construction/placement/material-transfer-vehicles/) or by depositing the mixture directly into the paver hopper), however on some very low traffic applications the mixture can be placed by a motor grader. Because of the larger [maximum aggregate sizes](https://pavementinteractive.org/reference-desk/materials/aggregate/gradation-and-size/) of the graded mixture, the minimum lift thickness for placement is usually around 50 mm (2 inches). 5. **Compaction**. The placed mixture is compacted to the desired density. Typical compaction efforts involve a large [pneumatic tire roller](https://pavementinteractive.org/reference-desk/construction/compaction/compaction-equipment/) and a large [vibratory steel wheel roller](https://pavementinteractive.org/reference-desk/construction/compaction/compaction-equipment/). If an emulsion additive is used rolling is typically delayed until the emulsion begins to break. If a portland cement or fly ash additive is used, rolling should begin immediately after placement. 6. **Fog seal**. If the newly placed material is to operate as a high quality gravel road then a fog seal is usually applied over the top to delay [surface raveling](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/raveling/) of the cold recycled mix. A fog seal is necessary over CIR using a portland cement or fly ash additive not only to delay surface raveling but also to provide a curing membrane for the additive to properly set. 7. **Surface course construction**. On higher volume roads, the cold recycled mix is overlaid with either a BST or a [thin HMA overlay](https://pavementinteractive.org/glossary/thin-hma-overlay/). In either case, a [tack coat](https://pavementinteractive.org/reference-desk/construction/site-preparation/tack-coats/) should be used to provide a good bond between the cold recycled mix and the [surface course](https://pavementinteractive.org/glossary/surface-course/). ## Purpose Stabilized base course or a low volume road granular surface course. ## Materials Recycled material and a binding additive (usually [asphalt emulsion](https://pavementinteractive.org/reference-desk/materials/asphalt/emulsified-asphalt/), lime, portland cement or fly ash). ## Mix Design No generally accepted mix design method, but the Asphalt Institute recommends and most agencies use a variation of the [Marshall mix design method](https://pavementinteractive.org/reference-desk/design/mix-design/marshall-mix-design/) (FHWA, 2001b[^2]). ## Other Information CIR is best suited for cracked pavements with structurally sound, well drained bases and subgrades. CIR is generally not appropriate for repairing pavement failures caused by: - [Rutting](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/rutting/) from excessive asphalt content or mix instability - Wet, unstable base, subbase or subgrade materials - [Frost action](https://pavementinteractive.org/reference-desk/design/design-parameters/frost-action/) - [Stripping](https://pavementinteractive.org/reference-desk/pavement-management/pavement-distresses/stripping/) CIR is generally suitable for lower volume roads that may only require a simple surface treatment over the resulting stabilized base course, or at most a thin HMA [wearing course](https://pavementinteractive.org/glossary/wearing-course/) (Better Roads, 2001[^3]). For projects using an [asphalt emulsion](https://pavementinteractive.org/glossary/asphalt-emulsion/) additive, typical specified minimum atmospheric temperatures range from 10 to 16°C (50 to 60°F). For projects using portland cement or fly ash as the additive, the minimum required temperature is 4°C (39°F) with no freezing temperatures expected in the next 24 hours (AASHTO, 1998[^1]). CIR requires sunny, dry conditions in order for the additive to properly set. If an asphalt emulsion additive is used, it is usually added at a rate of between 0.5 to 2 percent by weight of RAP. ## Sources [^1]: American Association of State Highway and Transportation Officials (AASHTO) (1998). Report on Cold Recycling of Asphalt Pavements. AASHTO-AGC-ARTBA Joint Committee Task Force 38 Report. American Association of State Highway and Transportation Officials. Washington, D.C. [^2]: Federal Highway Administration (2001b). Reclaimed Asphalt Pavement User Guideline: Asphalt Concrete (Cold Recycling). Web page on the Turner-Fairbanks Highway Research Center web site. Accessed 16 October 2001. https://web.archive.org/web/20150405042130/http://www.tfhrc.gov/hnr20/recycle/waste/rap131.htm [^3]: Better Roads (2001). Full-Depth Reclamation. Better Roads. Special insert section on full-depth reclamation in cooperation with the Asphalt Recycling and Reclaiming Association.