Although they might not realize it, people drive over and walk across David Darwin's work every day.
His specialty, concrete, reaches into more aspects of daily life than meets the eye. And soon, Darwin, Deane E. Ackers Distinguished Professor of Civil, Environmental and Architectural Engineering, will hold one of the most influential positions in the concrete industry: president of the American Concrete Institute.
"Anything you can think of involving concrete is likely covered by the American Concrete Institute," Darwin said. "It's the main concrete technical institute in the United States."
The institute studies, oversees and seeks to improve the work of structural engineers, contractors, material synthesists and bridge builders. It also studies specific topics such as nuclear safety, design for seismic activity, protection against corrosion and problems associated with the construction of massive concrete structures, such as dams.
Darwin, who assumes the presidency next month, will take the institute's work beyond U.S. borders. As the organization's spokesperson, he already has engagements to speak in Poland in May, the Netherlands in September and Greece in October. The institute has chapters worldwide, and he will meet with representatives from chapters in Europe, Africa, the Middle East and Asia.
Darwin has a long history with the institute, having joined as a student in the late '60s. He has been the Kansas chapter librarian since the early '80s. The chapter's library is located in Learned Hall.
"I think I have the longest tenure as a chapter librarian in the United States," he said with a laugh.
Elected by the institute's entire membership, he is finishing a two-year term as vice president. His term as president will last one year, and he will then serve as past president for three years. In addition to his speaking duties as president, he will chair the executive committee and the board of directors.
Darwin said his goals as president include continuing to support the organization's work in certification for those who work with concrete, getting students more involved in the organization and working more closely with the government and organizations such as the U.S. Army Corps of Engineers.
One of the institute's top priorities is sustainable development, a major focus of Darwin's research. He researches three major areas: methods to protect concrete, reduction in cracking and the bond between reinforcing steel and concrete, especially in relation to bridge decks. All three can lead to bridges that last longer, deteriorate more slowly and ultimately save money for taxpayers and travelers.
In the first level of Learned Hall, Darwin simulates the havoc Mother Nature can wreak on bridge decks. In what's been called a "time machine for concrete," he can replicate weather conditions at an accelerated pace. The device duplicates the salt that is placed on roads and bridges to help thaw ice during winter months. However, the salt can leak through cracks in the bridge's deck and corrode the reinforcing steel. The machine also replicates summer heat, generating temperatures as high as 100 degrees.
"We put on lots of salt," Darwin said of the device. "In one year we can simulate 25 years of exposure, and in two years we can simulate 50."
He tests different mixes of concrete and types of reinforcing steel to find out which hold up to the exposure best. The mixes are also put to the test in a humidity-controlled tent to check which is most resistant to cracking. In the tent, the temperature and humidity are held constant, while dozens of different mixes are studied to see which will make the best bridge deck.
The methods Darwin has studied are finding their way out of the lab and onto roads. Darwin and his colleague at the Transportation Research Institute, JoAnn Browning, associate professor of civil, environmental and architectural engineering, are well into a pooled fund study with 15 state departments of transportation and the Federal Highway Administration to build 20 bridges throughout the region using the techniques developed at KU. The deterioration rate of the bridges will be compared to other bridges built without the same methods. The two professors, along with graduate students, also regularly survey bridge decks throughout the state to study causes of deterioration.
Other techniques advocated at KU, such as using less cement and water to mix concrete, reducing concrete temperature and slow drying of concrete are being adopted by the industry, he said. The techniques lead to bridges that will last at least 75 years. They may cost more to construct, but the reduced maintenance and repair costs justify the initial cost many times over.
"Our procedures are just good concrete construction practices. It's taking what we know and putting it to work in the field," Darwin said. "Everybody alive today should be dead before these bridges need to be replaced."
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