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Wednesday, 17 July 2019
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Raw materials & technologies, Technologies

“Internally cured” concrete to improve bridges

Monday, 11 February 2013

According to Purdue University researchers, new high-performance concrete could reduce maintenance costs and allow bridge decks to last longer.

The new concrete could help bridge decks to last longer

Source: Zhenya Kovalyov/ Fotolia

The new concrete could help bridge decks to last longer

Source: Zhenya Kovalyov/ Fotolia

Researchers of Purdue University (Indiana, USA) have developed a new "internally cured" high-performance concrete that could reduce maintenance costs and allow bridge decks to last longer, according to Jason Weiss, a professor of civil engineering and director of Purdue's Pankow Materials Laboratory.

"Our testing indicates that internally cured high-performance concrete experiences substantially less cracking and concrete damage caused by deicing salt and, when properly designed, the service life of bridge decks can be greatly extended." The Joint Transportation Research Program, a partnership between the Indiana Department of Transportation (INDOT) and Purdue, worked with Weiss and INDOT to create specifications for implementing the internally cured high-performance concrete. It will be used on four bridges this year.

Additional water pockets inside the concrete

Concrete is normally made by mixing portland cement with water, sand and stone. In the curing or hardening process, water helps the concrete mixture gain strength by reacting with the cement. Traditionally, curing is promoted by adding water on top of the bridge deck surface. The new technology for internal curing provides additional water pockets inside the concrete, enhancing the reaction between the cement and water, which adds to strength and durability. The water pockets are formed by using small porous stones - or lightweight fine aggregate, as it is known in the industry - to replace some of the sand in the mixture.

"A key step in the process is to pre-wet the lightweight aggregate with water before mixing the concrete," Weiss said. "Nearly five years of research has been performed to fully understand how to proportion these mixtures and the level of performance that can be expected."

The internal curing process also allows engineers to reduce the amount of portland cement used in the concrete by replacing a portion of it with supplementary materials, such as silica fume, fly ash and limestone. These supplements will reduce the waste stream, the need for raw materials and the carbon footprint of making concrete while improving its durability, Weiss said.

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