100-year study mirrors U.S. history of concrete (w/ Video)

Almost since the beginning of recorded history, people have used concrete substances in everything from infrastructure to artwork.

In the second century B.C., for example, the Romans combined powdery , lime, stone aggregate and water to form hydraulic , an extremely hard, strong material that revolutionized their architectural designs and literally became the foundation of the massive Roman maritime infrastructure.

While pieces of some of these early Roman harbors, breakwaters, bridges and other structures still exist, as recently as the early 1900s, there had been little scientific research of concrete and only a few standards existed to guide its modern-day mixing and implementation. In fact, what now is the American Concrete Institute formed when editors of the publication Municipal Engineering noted in September 1904 the need for an association to deal with unsatisfactory concrete conditions. More than 600 people attended its first convention and exposition.

Shortly thereafter, Owen Withey, a professor of mechanics at the University of Wisconsin-Madison, had the vision and ambition to begin what likely is the longest-running university concrete research project in the country. "The project uses materials that were available at the time," says Steven Cramer, a UW-Madison professor of civil and environmental engineering. "It's just sand, stone, cement and water."

Withey's 1910 concrete study began at UW-Madison back in the day when universities conducted self-funded research simply for the pursuit of practical knowledge. And practical it was: Homes, high-rises, sidewalks, roads and bridges — some of which are still in service today — became ever-increasing parts of the U.S. landscape. Debuted in 1908, Henry Ford's mass-produced Model T opened the door of travel to middle-class Americans. The vehicle's slim, puncture-prone tires fared better on paved streets and roads — and, as people looked to the government to provide better roads, President Woodrow Wilson in 1916 signed the first Federal Aid Road Act to help states finance road building.

At the time of his project's inception, Withey had been a faculty member at UW-Madison for just five years. Planning tests at regular intervals, he and his students cast 100 years' worth of concrete samples, which, says Cramer, have been in both wet and dry storage under the university's tender-loving care ever since. "They decided that knowing the long-term properties of concrete would be a very valuable contribution," he says. "They did it with no idea their experiment would ever be sustained. Step by step, the institution was there."

A slim, stern-looking man with a direct gaze, Withey was active on several American Concrete Institute committees and served as institute president. When he published 20-year results of his research in 1931, the institute had grown to some-2,500 members, including architects, engineers and concrete manufacturers. "You can see the project tracking along with the growth of the industry — and the country — step by step," says Cramer.

In total, Withey and his students cast more than 2,500 concrete cylinders in 1910, 1923 and 1937 for the research program, and he continued the study even after becoming College of Engineering dean in 1946. He retired in 1953 and published the project's 50-year research results in 1961.

In the interim, Withey began to pass the research off to Kurt F. Wendt, a mechanical engineering faculty member who later succeeded Withey as engineering dean. With George Washa, who in 1938 earned the very first Ph.D. granted by the UW-Madison Department of Engineering Mechanics and later joined the university as a professor in that department, Wendt reported 50-year results based on the 1923 castings. They noted that, under outdoor storage, the concrete made with coarsely ground cements with high carbon disulfide content had increased compressive strength, while concrete made with finer cements and relatively low carbon disulfide content had reached its maximum strength 25 years or more prior.

Former students called Washa an inspiration and a model to emulate, praising his professional integrity, willingness to help them, and dedicated service to the college and university. Cramer was an undergraduate in one of Washa's last classes and, with Washa and engineering mechanics professor Jesse Saemann, tested the 1937 specimens at the 50-year mark. They found compressive strength at 50 years showed little change from the strength at 10 years.

Throughout the past 100 years, each of the researchers conducted additional tests at various intervals. Today, however, Cramer is the only one left — and this fall, Withey's 1910 longitudinal research project concluded under him. (Specimens from Withey's 1923 series still exist, ready for testing in 2023.)

Because his predecessors kept good records, Cramer knows exactly what went into the concrete mix and how it has performed in past tests. He and his students crushed the last of the 100-year-old samples in a slightly dusty, first-floor laboratory in Engineering Hall on the UW-Madison campus. They used a mammoth device called the million-pound test machine, which, using hydraulic pressure, exerts 50,000 pounds of pressure per minute on the concrete cylinders. Based on past results, the researchers tracked how much force it took to break each specimen.

Unlike Withey, Wendt and other early researchers, Cramer and his students also used modern-day tools, including microscopy, to study structural and chemical changes in the concrete. "What our contribution will be is the entire history of the life of these concrete specimens — what they were made out of, what the cement chemistry was at the time, the environmental conditions that they were exposed to, and then the properties at various points in time, from one week to two months, to 10 years to 30 years, to 50 years to 100 years," says Cramer. "There's a wide variety of facilities that have already exceeded their design life, and we'd like to be able to extend the design life. That often means the period between a 50-year-old structure and a 100-year-old structure. We'll now have properties to fill in that 50- to 100-year period."

Like their predecessors, he and his students will publish the results. And that will close this century-old project — though the 1923 castings remain to mark yet another 100-year anniversary. "What's unique is there's not a laboratory study that has had the longevity of 100 years that one institution has been able to maintain," says Cramer.

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Citation: 100-year study mirrors U.S. history of concrete (w/ Video) (2010, December 17) retrieved 27 January 2020 from https://phys.org/news/2010-12-year-mirrors-history-concrete-video.html
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