Sunday 21 September, 2014

Insulating high-speed tracks against freezing, thawing

Published On: Tue, Oct 30th, 2012 | Transportation Science | By BioNews

Researchers are helping high-speed rail systems handle the stress of freezing and thawing in extreme or unpredictable weather conditions.

As high-speed rail systems become common worldwide, it becomes essential to keep passengers safe and insulate the rail system against freezing and thawing conditions, said Kyle Riding, assistant professor of civil engineering at Kansas State University (KSU) in the US.

Riding is leading a three-year study that looks at the freeze-thaw durability of concrete railroad ties (concrete sleepers), on which the tracks are embedded, vital to developing safe and durable high-speed rail systems.

Riding is working with Mohammed Albahttiti from the United Arab Emirates; KSU Institute of Environmental Research, colleague at the University of Illinois at Urbana-Champaign, and Canadian National Railroad and CXT Concrete Ties Inc, according to a KSU statement.

“Freeze-thaw is a stressor that happens in pretty much all concrete when it is exposed to water and then freezing and thawing temperatures,” Riding said.

When water freezes, it grows in size by roughly nine percent, Riding said.

These increases, coupled with the decreases when the ice melts, cause stress on the container the ice forms in. When too much stress occurs, the container can break — similar to what happens when a full soda bottle is left in the freezer.

In concrete rail sleepers, water collects and freezes in the pores of the concrete. As the liquid freezes, it creates stress in the sleeper, which can crack them.

High-speed rail systems are more sensitive to these problems because of the high speed at which the trains travel on the tracks.

To study the freeze-thaw conditions in concrete rail ties, researchers will add surfactants to the concrete as it is being mixed in the lab. These compounds produce millions of microscopic bubbles in the concrete that act as pressure release valves to help protect the concrete against damage.

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