November 7, 2012

GEORGE SWAN/WIKIMEDIA COMMONS

A cement mixer and cement pumper work in tandem on King Street in Toronto, Ont.

Concrete sustainability requires coordinated research into hydration, believes expert

PETER KENTER

correspondent

While the metallurgical and semiconductor industries have benefited from a deeper understanding of chemical processes that underlie productivity improvements, the concrete industry is falling behind.

In large part, that can be attributed to a lack of thorough understanding of the chemical processes involved in the hydration of portland cement, says Maria Juenger, associate professor, University of Texas at Austin.

Juenger says that miracle metals, polymers, pharmaceuticals and semi-conductors were developed through an understanding of chemical kinetics — the study of rates and mechanisms of chemical reactions and of the factors on which they depend. By mastering kinetics, concrete producers can also maximize sustainability.

“Using kinetics, we can look at the life cycle performance of our concrete,” she says.

“With that understanding we can optimize the durability, optimize the cost and minimize the environmental impact.”

She notes that, while some research has promoted advances in concrete technology, the industry lacks any sort of coordinated research effort that would lead to a thorough understanding of the underlying chemistry behind hydration.

“Ultimately, a more coordinated effort needs to be assembled that enables research teams to focus on specific tasks identified within a roadmap for developing a comprehensive description of cement hydration rather than individual efforts being spent on isolated tasks,” says Juenger.

A roadmap for coordinated research was developed at the International Summit on Cement Hydration Kinetics and Modeling held at Laval University in 2009 and championed by Joseph Biernacki, professor of Chemical Engineering at Tennessee Technological University, among others.

“As engineers the means we have at our disposal are primarily composition and processing,” she says.

“The vision Joe has is to optimize the materials going in on the composition end — the admixtures, the cement, the aggregate and water — and the processing of those materials to achieve the desired end and not look at the process in between as a black box. Let’s try to engineer these hydration processes in the middle that are affecting our setting time and durability in a way that isn’t simply trial and error but engineered.”

Juenger notes that concrete mixtures employing fibres, admixtures that control shrinkage and super plasticizers are no longer cutting edge technology.

“Those are not emerging technologies,” she says.

“Those are proven technologies. Right now we’re up against a wall. If scientists don’t understand the chemical process, we can’t manipulate them. Our key to make dramatic changes in the way concrete performs is to make dramatic changes in the way that we understand concrete.”

The industry is also failing to take advantage of the most sophisticated tools available for materials research, she says. That, however, is changing as concrete researchers begin to employ such tools as nano-x-ray tomography and vertical scanning interferometry, which examine chemical processes at a minute scale.

Juenger says that effective molecular modeling is also essential to achieve the type of understanding necessary to make breakthroughs.

“We don’t yet have universal software tools or a universally accepted platform for modeling,” she says.

“We have a lot of separate platforms that can’t easily be combined in a cohesive manner. We’re getting closer, but we’re not there yet.”

Juenger spoke at the Fall 2012 convention of the American Concrete Institute held in Toronto.

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