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Roads required constant maintenance. The typical fix was to seal the widening cracks, dig out and replace failed areas, and place thin asphalt overlays in an attempt to keep the road together.

Cumulatively, this had the effect of wrinkling the road surface, creating an inconsistent and rough ride, and requiring additional repairs often less than six (6) months later.

Repair strategies would temporarily fix the surface, but never solve the problem.

As roads continue to fail and budgets become increasingly tight, it is timely to get a best alternative to maintaining the roads.

The solution came in the form of Cold Foam In-Place Recycling. Unlike other rehabilitation options, the cold foam in-place recycling is building a new structural section.

Until the mid-1990s, almost all cold-in-place recycling involved the use of emulsions. In recent years, countries and states began to turn instead to foamed or expanded asphalt.

Many parts of the world have used cold foam in-place recycling for years in their road rehabilitation projects.

The cold foam in-place recycling typically consists of three materials – 2.5 percent liquid asphalt, 1 percent bulk cement and various amounts of water.

The cold foam process excavates the pavement to a depth below the bottom of the asphalt and into the existing base material.

While the pavement recycler pulverizes the material, hot paving oil (bitumen) is mixed with cold water and air creating a foaming action.

The pulverized material is carried up through the cutter housing headspace with the heavier material remaining closer to the drum and the lighter, finer material being suspended between the cutter head and housing.

The foamed asphalt coats the finer, flour-sized material which then acts as the “glue” that holds the new, thicker stabilized base together.

Unlike typical asphalt that is finished when it is cold, the cold foam in-place material isn’t finished until it is compacted.

Compaction is by 15-ton steel drum rollers in 3 to 4 passes often achieving 98 to 105 percent density.

Once compaction achieved, pneumatic rollers is used to bring the fines up and knead it together to get the finished surface.

Maintenance crews are able to complete recycling at 20 to 30 feet per minute.

Within a few hours, the surface was dried and a 10-12 hundredths of fog seal will be applied followed by sand.

The foam process leaves a crust on top, and that needs to be protected with a fog seal.

The result is a stronger, longer-lasting pavement at a fraction of the cost and in a fraction of the time when compared to conventional reconstruction.

The cold foam process rebuilds the road from the bottom up, eliminating symptomatic problems associated with the existing road bed such as reflective cracking and shallow base failure. Utilizing all of the existing road bed materials, the process eliminates the need for aggregates to be trucked-in and waste materials to be trucked-out.

Reduced truck traffic to and from the job site translates into reduced fuel consumption, emission levels, heavy-vehicle associated damage to the road, and delay to the public.

Rebuilding the roadway at a rate of 3 km or more per day, not only decreases the inconvenience to the public compared to conventional road replacement, but also decreases the exposure of workers during the reconstruction.

The increased service life reduces the need for future rehabilitation or replacement.

Cold foam in-place recycling is a viable and cost-effective alternative to conventional dig-out & overlay or gut-out & re-build construction.

Source : Tech TransferNewsletter (2003); For Construction Pros: Introducing Cold Foam Asphalt Technology: Marshall, Mike, (2001) Cold foam in place recycling Ellerslie Road, City of Edmonton, revisited and Use of Foamed Asphalt with Cold-in-Place Recycling and Full Depth Reclamation : Information on implementation, Local Road Research Board, Department of Transportation, Minnesota

(this article written for 1BINA.my)