Jan 7, 1998
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Christian Basi
Sr. Information Specialist
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MU SCIENTIST WORKS TO CEMENT FORMULA FOR STRONGER CONCRETE
COLUMBIA, Mo. -- For hundreds of years, the Coliseum in Rome has stood as a marker of an era gone by. Yet concrete driveways poured only a few years ago are already developing cracks. Ron Berliner, a scientist at the University of Missouri Research Reactor Center, is determined to find out why.
"People have been making cement for a very long time, but they know very little about it," Berliner said. "Cement is a very poorly characterized material. It's very difficult to understand both physically and chemically." Berliner's research, which focuses on strength and durability of concrete, could prove beneficial to the environment. For every ton of cement that is made, one-half ton of carbon dioxide is released into the air. Currently, the world produces about 350 million metric tons of cement every year, 80 million metric tons in the United States alone. It is estimated that 10 percent of man-made greenhouse gasses are the result of cement production. Berliner's research could improve the strength of cement, leading to a decreased need for the material.
"If we understand what contributes to the strength and durability of cement, we can arrange its formation to make a stronger and more durable concrete," Berliner said. "New technology would allow us to construct buildings at a much lower cost because they would not use as much steel for reinforcements. We are hoping to drop those costs and help out the environment with stronger conrete. Less cement used means less needs to be made and we, in turn, release less carbon dioxide into the atmosphere."
The first goal of Berliner's research is learning how to monitor the progress of the chemical reactions in cement. To study the chemical reaction, Berliner exposed a cement specimen to neutrons and observed the rate at which water combined with the dry cement. Currently, scientists don't have much control over the cement hardening reaction.
"The Romans mixed in ox blood when they wanted to speed up cement hardening," Berliner said. "The hemoglobin in the blood makes the concrete stronger. People have known for a long time that a minute amount of sugar keeps cement from hardening too quickly. We know of chemicals that work in speeding up or slowing down the reaction, but the real understanding of why and how the chemicals work is limited."
In order to make a "map" of the cement structure and study the rate of the chemical reactions, Berliner uses neutrons produced at the MU reactor. The way that neutrons scatter off a cement specimen provides information on the atomic structure of the cement. In addition, neutrons that gain or lose energy when they scatter are an indicator of the progress of the cement hardening reactions. This aids researchers in mapping the structure of cement and determining what has happened at different stages during the hardening reactions.
"When you mix cement with water, the hardening reaction starts immediately, but a kind of concrete crust is formed around each grain, and it takes a while for the remaining water to reach the cement on the inside," Berliner said. "After 24 hours, the concrete is at about 75 percent of its strength, but in reality, the chemical reaction never stops. It just gets slower and slower." How the water reacts to the cement and what happens at that time are questions that Berliner hopes to address with his research.
Berliner's recent findings were published in the journal of Cement and Concrete Research. His work is being funded by the Federal Highway Administration.
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