PITTSBURGH – Anyone who works in construction knows the difference between cement and concrete. Cement is an ingredient. It is the powdery substance that mixes with aggregates and water to form concrete, which is the final product.
In some circles, distinguishing between the two is a contentious matter. The internet even popularized a meme of a wiener dog wearing a tux growling, “Cement? Das conk creet, baybee!” And if you can’t trust a sausage-shaped pup in his wedding suit to know the difference between the two, at the very least, you can trust one of our engineers.
“Cement is to concrete as flour is to fruitcake,” said Brian Lucarelli, a concrete materials engineer for the U.S. Army Corps of Engineers Pittsburgh District. “It’s a phrase that someone at the Engineer Research & Development Center often says when they teach the concrete fundamentals class.”
Not everyone is a fan of fruitcake, however, so let’s use a bread analogy as a substitute.
Like many types of bread that exist in the world – baguette, focaccia, rye, rustic, sourdough, bagels, naan – not all concrete is made or used the same way. Some concrete mixtures are better suited for mass constructions, such as gravity dams, while others are specialized for underwater use, designed to avoid falling apart in the wet.
Engineers have developed and tested concrete mixtures to overcome all kinds of environmental demands, but one construction category has evaded engineers for centuries until now: cold weather.
“If concrete freezes too quickly after being poured, it significantly reduces its long-term strength and durability,” said Brian Lucarelli, a concrete materials engineer for the U.S. Army Corps of Engineers.
A team of concrete experts at the Pittsburgh District assisted the research and development of the Additive Regulated Concrete for Thermally Extreme Conditions, or ARCTEC. Even the acronym sounds like it’s dropping cold, hard facts.
“ARCTEC is a concept where concrete is self thermally regulating in extreme temperatures such as hot summers and frigid winters,” said David Noll, also a concrete materials engineer with the Pittsburgh District. “Ordinary concrete requires additional thermal protection, whether heating or cooling, which drives up cost and delays schedules.”
Pittsburgh engineers began collaborating with the U.S. Army Engineer Research and Development Center in late 2020 to develop ARCTEC, along with the Maine Army National Guard and other USACE offices.
“ERDC is the research and development arm of the corps,” said Noll. “They provide invaluable research and innovation.”
The technology allows contractors to pour concrete in temperatures between 20 and 40 degrees Fahrenheit without needing heated tents, insulated formwork, blankets or diesel heaters. Those methods add time and cost to cold-weather construction. ARCTEC technology will be very useful in Pittsburgh, which faces cold, unpredictable winters that often shorten or halt construction seasons.
Testing for ARCTEC took place at the Cold Regions Research and Engineering Laboratory in New Hampshire, one of the ERDC sites. It runs a facility the size of an airplane hangar, kept below-freezing temperatures throughout the year.
“ERDC has some incredible facilities,” Lucarelli said.
ARCTEC is accomplished with commercially-available concrete admixtures. However, the research is still ongoing to determine recommended dosages for optimal performances at various ambient temperatures.
Research has shown that when concrete freezes too quickly, it becomes 90 percent weaker than if cured at normal temperatures. The ARCTEC concept seeks to prevent rapid freezing, allowing the concrete to protect itself without additional measures.
The next mega project in the Pittsburgh District will construct a new navigation chamber at the Montgomery Locks and Dam on the Ohio River. The district will assemble a concrete batch plant on site to deliver a minimum of 150 yards of concrete per hour.
The plant will produce at least nine different types of concrete, each tested and validated in a lab on site. The ARCTEC process has no proprietary elements, meaning government and private agencies will benefit from this technology in the future. Project contractors can choose to use ARCTEC technology during winter months at Montgomery.
In the meantime, no research lab anywhere recommends adding cement to your bread recipes. It is not the healthiest alternative to gluten-free flour.