Cold In-Place Recycling: How CIR Rebuilds Old Asphalt

Cold in-place recycling, usually shortened to CIR, rebuilds a tired asphalt road by grinding up its top few inches, blending the grindings with a new binder and laying the mix right back down, all without heating it. The road keeps most of its own material, fewer trucks haul old asphalt away and new stone in, and the recycled layer becomes a sturdy base for a fresh surface. This guide walks through how the process works, where it fits and where it does not.

Asphalt tonnage calculator →

The short version

What it treats: the asphalt layer only. Guidelines from the Asphalt Recycling and Reclaiming Association (ARRA) describe treatment depths of about 2 to 5 inches, most often 3 to 4.
What gets added: a recycling agent, either emulsified asphalt or foamed asphalt, plus water and sometimes cement, lime or extra aggregate if the mix design calls for it.
What goes on top: a new wearing course, usually hot mix asphalt.
What it cannot fix: a failed base or soft subgrade. That calls for deeper work such as full depth reclamation.

How the CIR process works

Most crews run a line of machines nicknamed a recycling train. Some contractors use a single large recycler that does several steps in one unit, but the sequence is the same.

Milling. A large cold planer cuts the old pavement to the planned depth. If you have never seen one, our page on the road milling machine shows how the cutting drum works.
Sizing. The grindings pass over screens, and oversized chunks go through a crusher so the material has a controlled maximum size.
Mixing. A pugmill blends the sized grindings with the measured recycling agent and water. Rates come from a lab mix design, not guesswork.
Placing. The mix drops into a windrow, gets picked up and is laid by a paver much like regular asphalt.
Compacting. Rubber-tired and steel-drum rollers press the mat down. ARRA notes the recycled layer does not compact back to the exact depth that was milled, because the processed material takes up more room, so specs state whether the depth means milled depth or finished depth.
Curing and surfacing. The mat is left to lose moisture, then a new surface goes on.

Emulsion vs foamed asphalt

Both recycling agents do the same job: they coat and bind the old stone and aged binder into a flexible, cohesive layer. The difference is how the fresh asphalt is delivered.

Emulsified asphalt is asphalt broken into tiny droplets suspended in water. It mixes at road temperature and "breaks" as the water leaves. Our asphalt emulsion guide covers how that works.
Foamed asphalt is hot asphalt injected with a small amount of water and air so it expands into a foam for a few moments, long enough to spread through the cold grindings.

Federal Highway Administration (FHWA) guidance says older CIR specs often demanded two weeks or more of curing because they relied on solvent-based emulsions. Modern engineered emulsions cure much faster, and foamed mixes are often ready sooner still. ARRA recommends a minimum of three days and a moisture content of 3 percent or less before the surface course is placed.

When cold in-place recycling makes sense

CIR is a good match for roads whose trouble is mostly in the asphalt itself, while the layers underneath are still holding up. Typical candidates include:

Widespread cracking from age and temperature swings, especially cracks that keep coming back through thin overlays. See reflective cracking through an overlay for why patching over them rarely lasts.
Raveling, weathered surfaces and rutting confined to the upper layers.
Roads with enough asphalt thickness that the cut leaves sound material below to carry the equipment.

It is a poor fit when the base is pumping, the subgrade is soft or wet, or the asphalt is so thin that the mill would punch through into stone. Drainage problems also need to be fixed first, because no surface treatment survives a saturated base.

CIR compared with other recycling methods

Hot in-place recycling heats and remixes roughly the top inch or two. It handles surface distress but not deeper cracking. See hot in-place recycling.
Cold in-place recycling works deeper in the asphalt, cold, and builds a new base layer from the old pavement.
Full depth reclamation grinds through all of the asphalt and into the base, then stabilizes the blend. It is the deepest fix of the three.
Cold central plant recycling uses the same kind of cold mix, but the grindings are processed at a stationary plant and trucked back, which helps when a project has stockpiled millings or needs tighter control.
Mill and overlay removes old asphalt and replaces it with new hot mix. The millings leave the site. Compare it on our mill and overlay page.

Planning the overlay tons

The recycling itself is usually bid by the square yard, but the hot mix surface on top is bought by the ton. To rough out the overlay, multiply length by width for the area, multiply by the thickness in feet, and multiply by a density near 145 pounds per cubic foot for compacted hot mix. Divide by 2,000 for tons.

Example: one mile of road 24 feet wide is 126,720 square feet. A 2-inch overlay is about 21,120 cubic feet, or roughly 1,530 tons at 145 pounds per cubic foot. Our asphalt tonnage calculator runs the same math for any size, and the minimum asphalt overlay thickness guide covers how thin a surface lift can safely go.

Things that go wrong

Rain before the surface goes on. Wet weather slows curing and can soften the mat. Crews watch the forecast closely.
Surfacing too soon. Trapped moisture under a fresh overlay can weaken the bond and the recycled layer.
Skipping the investigation. Cores and testing should confirm the asphalt is thick enough and the base is sound before anyone picks CIR.
Ignoring the edges. Narrow shoulders and soft edges may need extra work so the recycled mat has support.

Questions people ask

What is cold in-place recycling?

It is a road rehabilitation method that mills the upper part of an old asphalt pavement, sizes the grindings, blends them with a recycling agent such as emulsified or foamed asphalt and lays the mix back down on the same road without heating it. A new wearing surface goes on afterward.

How deep does cold in-place recycling go?

Industry guidelines from the Asphalt Recycling and Reclaiming Association describe treatment depths of about 2 to 5 inches, with 3 to 4 inches the most common. The right depth depends on how thick the existing asphalt is and how much strength the road needs.

Does CIR need an overlay?

Yes. The recycled layer acts as a base and needs a wearing surface, usually a hot mix overlay. Some low-volume roads get a chip seal instead. ARRA guidance calls for at least three days of curing and low moisture in the mat before the surface goes on.

Can traffic drive on cold recycled asphalt right away?

Usually yes, at reduced speed. Federal guidance notes traffic is typically let back on at the end of the work day, slowed down so the fresh surface does not ravel before it cures.

What is the difference between cold in-place recycling and full depth reclamation?

CIR stays in the asphalt layer and leaves some old asphalt in place underneath. Full depth reclamation grinds through all of the asphalt and into the base, then stabilizes the blend as a new base. FDR is the choice when the base itself has failed.

Is cold in-place recycling used on driveways?

Rarely. The equipment train is built for roads and long runs. A worn driveway is normally fixed with an overlay or a remove-and-replace job instead.

As an Amazon Associate, AsphaltTons.com earns from qualifying purchases. Product links below are sponsored.