The most recycled material in the United States is not paper, aluminum, glass or plastic. It’s asphalt – 90 million tons of which are reclaimed from our roadways each year, and more than 80 percent of that is reused in some form.

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Asphalt is the black glue that holds roadway stone together. With an eye toward greening up the industry, paving companies are recycling and reusing old roadway materials, and asphalt manufacturers are working to make more eco-friendly products. PHOTO: Cold Mix Manufacturing

Cold Mix Manufacturing, an asphalt company in College Point, New York, developed GreenPatch, one of the first eco-friendly pothole fillers. The company has a distribution facility in Indiana to serve the Midwest. The goal is to make GreenPatch available to consumers. PHOTO: Cold Mix Manufacturing

GreenPatch is a permanent repair that remains stable as long as the surrounding pavement is sound. Application is the same as traditional cold-mix asphalt. Sweep the area and apply GreenPatch directly out of the bag. Compact the mix and the job is done. PHOTO: Cold Mix Manufacturing

GreenPatch most often is used for edges, curbs, potholes, manhole seals and virtually any surface that needs a permanent repair. It also may be used with hot-mix asphalt. PHOTO: Cold Mix Manufacturing

GreenPatch is endorsed by the National Green Energy Council. The ready-to-use cold asphalt mix contains none of the petroleum-based solvents found in traditional mixes, which emit volatile organic compounds. VOCs contribute to respiratory ailments, create smog, contaminate soil and poison groundwater. GreenPatch contains no VOCs. PHOTO: Cold Mix Manufacturing

GreenPatch uses 40 percent recycled asphalt and can be ripped up and recycled. The softener in GreenPatch is biodegradable and safe for the environment. It is manufactured at a lower temperature than conventional mix, reducing fuel consumption by 70 percent. PHOTO: Cold Mix Manufacturing

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Paving the way to a greener world

Asphalt is a sticky, viscous substance that binds together the crushed stone and gravel (aggregate) in roadways and waterproofs the surface. It’s produced by distilling the residues from petroleum refining. Long associated with smoky chimneys, in the past decade the asphalt industry has introduced several environmental initiatives to clean up its image in every sense.

Several Indiana companies have invested significant resources to purchase equipment and train employees to produce and install more eco-friendly asphalt. Here’s a look at some of their initiatives.

Asphalt recycling
Asphalt is reclaimed from the roadways by machines that grind off the surface. This asphalt/aggregate mixture is taken to a plant where it is pulverized. It is then mixed with more liquid asphalt, laid back on the roadway and coated with asphalt again to waterproof and seal the surface.

According to Buck Ritz of Milestone Contractors, recycled asphalt has been proven to be as resilient as conventional asphalt and saves more than 25 percent of the cost of a complete reconstruction. It also reduces consumption of natural resources.

Ron Terrell of Milestone Contractors estimated that about 75 percent of the company’s product contains some recycled material. He expects that to increase as more government agencies learn about it.

Porous pavement
A relatively recent initiative, porous pavement is a coarse asphalt laid over a stone leaching bed. It allows rainwater to filter through the porous surface into the retention bed below instead of immediately running off the surface, flooding streams and storm sewers. The leaching bed functions as a natural filter for the petroleum and oil drippings in the water, gradually releasing clean water into the soil.

Porous pavement is used for parking lots and other large, flat areas. Because it does away with the need for separate retention ponds, porous pavement is a more effective use of land, especially in commercial developments.

Warm-mix asphalt
Asphalt requires very high temperatures to remain pliable. As it cools, it starts to harden. Anyone who has been in a construction zone has seen the heat literally ripple in the air as the roadway is laid. A new process allows asphalt to be laid at a significantly lower temperature.

“Conventional asphalt must get to 320 degrees Fahrenheit,” explained Charlie Holland, technical director of the Asphalt Paving Association of Indiana. “Warm mix can be used at 280 degrees, and performs in the same way as conventional asphalt.”

The lower temperature reduces the fuel required to mix the asphalt and reduces fuel emissions in the construction zone. The Indiana Department of Transportation has approved the use of warm-mix asphalt on roads with low-volume traffic.

The way of the future
Cold-mix asphalt is another alternative to traditional asphalt. It can be stockpiled and used at cooler temperatures for minor repairs such as filling potholes. The down side is, to make it spreadable at cooler temperatures requires adding petroleum-based softeners such as diesel and kerosene. Those additives give off harmful emissions known as volatile organic compounds.

In its push to be green, the asphalt industry is experimenting with synthetic and organic compounds that might reduce emissions from roadways themselves. While most of these aren’t yet widely available for consumer use, demand will increase supply.

—By Vasanthi Vasudevan, for Custom Publications

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