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Materials

Concrete creep mechanism explained

Discovery could assist development of deformation-resistant structures

by Elizabeth K. Wilson
August 8, 2016 | APPEARED IN VOLUME 94, ISSUE 32

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Credit: Shutterstock
Concrete creep leads to crumbling, as seen in this bridge in Ottawa, Ontario.
Credit: Shutterstock
Concrete creep leads to crumbling, as seen in this bridge in Ottawa, Ontario.

Concrete is ubiquitous as a building material, but it suffers from “creep,” long-term deformations caused by its own weight, that damage its integrity and make it susceptible to cracking and crumbling. Now, scientists have evidence this creeping phenomenon stems from nanoscale dissolving of concrete’s primary phase, calcium silicate hydrate (CSH) grains, under high stress (J. Chem. Phys. 2016, DOI: 10.1063/1.4955429). The discovery, by a team led by Gaurav Sant, Mathieu Bauchy, and Isabella Pignatelli at UCLA, could allow further study to devise concrete compositions that are more resistant to creep. Concrete—various mixtures of sand or gravel with a binder and water—has been used as a building material for thousands of years, and today, next to water, it’s the most widely used material in the world. Scientists have proposed models for concrete creep mechanisms, but none have been able to explain all of the physical manifestations of creep. In the new work, the researchers combined experimental data, such as vertical scanning interferometry, which measures nanoscale mineral dissolution, with molecular dynamics simulations of the behavior of various CSH compositions. They showed that CSH grains dissolve under high stress, and re-precipitate at low stress. They also identified CSH variants that are less likely to creep.

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