Driving surface is placed immediately behind HIR heater-scarifying process.

Instead, HIR and CIR recycling methods are devised by specialty contractors, who use their own equipment designs – and creations – to execute in-place recycling in Canada, Mexico and the United States on a regional basis. They also will sell such machines to other contractors.

One such HIR contractor that began as a contractor and now sells equipment is Ecopave Systems, a wholly-owned subsidiary of Pyrotech Holdings. Ecopave says it’s a pioneer of the two-stage, hot-in-place asphalt recycling business, and now manufactures the Ecopaver 400 two–stage, hot-in-place asphalt recycling system.

The patented system or train consists of a preheater, two self-propelled heater/miller units and a pugmill. Following the train are a conventional paver and rollers. The Ecopaver 400 not only performs the recycling of existing roads to exacting standards, the maker says, but it also incorporates a full emission control system that makes the system virtually smoke free. The Ecopaver 400 is manufactured in British Columbia.

Re-Recycling Pavements

Roads can be recycled again and again using HIR recycling technology, says Patrick O’Connor, president, Pavement Savers, Cocoa, Fla.

In Mason County, Ill., Highway 15 is CIP-recycled to a depth of 3 to 4 in., depending on depth of existing asphalt.

“There is no reason a pavement manager could not continue to ‘re-recycle’ a road for as long as the road exists,” O’Connor tells Better Roads. “After all, what is asphalt made of? It’s 95 percent sand and stone, both a 50 million-year-old-plus material that does not change, and the other 5 percent is asphalt, another 50 million-year-old-plus material. The only change that takes place during the time it is on the road is the light ends of the 5 percent asphalt content that is lost, mostly to weathering.”

Pavement Savers employs a single-pass HIR recycling method in which the asphalt surface is heated by a preheater using radiant heating with no flames. This heating panel produces almost 2,000 degrees F of radiant heat in one minute, O’Connor said, distributing more than 80,000 BTUs per square foot evenly throughout the entire heating panel. “It’s the cleanest, safest, most economical and virtually smoke-free heating system in the world,” he says.

The preheater is followed by Pavement Saver’s hot-in-place recycler, which also uses radiant heater technology. After the surface has been heated, Pavement Savers applies an exclusive recycling oil just ahead of the scarifiers, using a spinner-droplet application. Then, the heated asphalt is scarified and the rejuvenating oil is mixed with the scarified asphalt not once, but twice, before it is re-leveled by a screed. A fresh asphalt overlay then can be placed with an asphalt paver.

A Train in Illinois

Recently, a self-propelled, single-pass recycling machine was put to work by contractor Dunn Company to cold-in-place recycle Mason County Highway 15 in central Illinois. Dunn reported an average cost on the job for the base course of about $26 per ton, compared to fresh hot-mix asphalt selling around $75 per ton at that time.

Following CIR recycling, a structural (intermediate) course layer was to be placed, followed by a friction course. The project length on the two-lane blacktop road was 17.4 lane miles, a total of approximately 112,000 square yards.

The road was in bad shape. Some pavement sections were more than four decades old, and the pavement was highly oxidized, alligator-cracked, with many irregular cold patches. Extensive transverse block cracking had occurred. Coring and as-built data showed the existing asphalt pavement thickness ranging from 5 to 6 inches in thickness. The project was to be divided into two recycling depths — two miles at a depth of 3 inches and the remainder at 4 inches. The emulsion content was calculated on a medium-to-coarse gradation percentage as 2.25 to 3.75 percent.

Bid documents for the CIR required a self-propelled, cold-milling machine capable of pulverizing the existing bituminous material in a single pass, with a minimum width of not less than 10 feet. The machine had to have automatic depth controls to maintain the cutting depth to within plus or minus 1/4 inch of specification, and had to have a positive means for controlling cross slope elevations. No heating device to soften the pavement was allowed.

The machine used was a Wirtgen 3800 CR recycler. In this compact recycling train, the 3800 CR pushed an emulsion tanker while simultaneously milling (downcutting) the existing pavement. The 3800 CR added the design percentage of emulsion, proportional to working speed, and a metered amount of compaction moisture to suit varying in-situ conditions, with water taken from an onboard tank.