It's a typical New England winter morning, a clear blue sky and bright sunshine have a dozen New Hampshire Department of Transportation workers squinting and shuffling around to stay warm, surrounded by steam from their own breath. The thermometer reads 5°F as a concrete truck rumbles down the hill, stops, and the men begin to set up the chute. A few minutes later, the high-slump mix is being poured into the curbing forms on a secondary road bridge. Researchers from the Engineer Research and Development Center's (ERDC) Cold Regions Research and Engineering Laboratory (CRREL) watch over the work and occasionally dip sample cups into the mixture. Thus, the experiment proceeds, and as the concrete starts to set-up, everything looks good.

Normally, concrete is not poured when the temperature is below 40°F, but a CRREL-designed concrete admixture stands to rewrite that long-held rule. After two years of laboratory and in-field testing, CRREL researchers say the admixture produces concrete as strong and durable as that poured in normal temperatures; furthermore, the cold-weather mix is one-third cheaper than a conventional alternative designed for cold-temperature placement. Ten states, including Vermont and New Hampshire, are underwriting extensive testing of the cold-weather concrete mix, which could extend the transportation construction season by up to 60 days in the northern United States, and 120 days in moderate climates.

Two readily available ingredients account for the differences between conventional concrete and the cold weather prototype, according to CRREL principal investigator Charles Korhonen. “The admixture accomplishes two things. We're lowering the freezing point of the concrete, similar to anti-freeze in a car's radiator, and we're forcing the concrete to gain strength faster than normal.”

Korhonen says motorists, in particular, should welcome the new technology. “Work normally done in the summer creates construction zones and slow moving traffic, leading to frustration and lost time. But if some projects can be moved to low-traffic winter months, there would be far fewer problems and roadway hazards for both drivers and workers.” Additionally, the process could improve transportation infrastructure in cold weather regions by extending the construction season, while allowing longer seasonal employment and greater use of construction equipment.

“We're rewriting how cold weather transportation concreting can be applied,” observes CRREL researcher Lynette Barna, who hopes to see the admixture process accepted by the concrete industy and commercial users. Previous to the development of the cold-weather admixture, concrete could be poured and cured in temperatures below 40° F only by using heated tents or thermal blankets to enclose the construction area.

“We're very pleased with the project right now. We've saved a lot of money and man hours by not having to use a heated enclosure,” affirms Leland Atwood, an engineer for the New Hampshire Department of Transportation.

The biggest hurdle in widespread use and availability of the cold-weather admixture is the lack of an industry standard. Though the American Society for Testing and Materials currently does not recognize the process, that may change soon. Korhonen believes “we've proven this works, so ASTM will hopefully develop standards, and then commercial producers will start to manufacture it, and my hope is that it's going to change many rules about concrete construction.” The admixture has been field tested so far in North Woodstock, Littleton and West Lebanon, N.H., and Rhinelander, Wis.

CRREL is one of seven laboratories that comprise ERDC, the premier research and development facility for the U.S. Army Corps of Engineers. With more than 2,000 employees and $1.2 billion dollars in facilities, ERDC oversees an annual research program exceeding $550 million. It conducts research in both the military and civil works arena. CRREL's mission is to gain knowledge of cold-weather dynamics through scientific and engineering research, and apply that knowledge for the benefit of the Department of Defense and the nation. Based in Hanover, N.H., with field offices in Fairbanks and Anchorage, Alaska, CRREL is the only Department of Defense laboratory addressing problems and opportunities unique to the world's cold regions.