CONSTRUCTION CORNER: Cement that "feels" in the works

A novel "smart" cement being developed for cementing oil or gas wells, could provide the construction industry with an improved way to monitor the health of most of the things it builds.

Right now, though, the new cement will be of value to the energy sector in the Unites States.

After drilling a borehole, oil and gas drillers insert a metal casing, which is held in place with standard cement, which adheres to the metal and bonds with the geological formation through which the hold was drilled. Typically, the cement casing is about five cm thick, and has an expected life of 30 years.

But the problem with the system is that there is no way to inspect the cement occasionally, no way to know how it is holding up or deteriorating. Cumaraswamy Vipulanandan, of the University of Houston, is addressing the problem by trying to make the cement more like human skin. The skin is thin, he notes, and is tactile. When someone touches your skin, you can feel it.

So to give cement the ability to "feel" the things it’s in contact with, he added stuff called piezo-resistive material to the cement. That makes the cement far more "sensitive" than any other cement which enables it to detect stresses, contamination levels, cracks, temperatures and fluid loss.

Scientists have known of piezoelectricity and piezoresistive effects since the middle of the 18th century. Piezoelectricity is simply electricity resulting from pressure. Piezoresistive effects are the changes in electrical resistivity of many substances when mechanical strain is applied. Many materials—metals, silicon and other semiconductors—when deformed even slightly—will produce an electric current.

For a long time, piezoresistive effects remained more a laboratory novelty than anything else. But they have gradually worked their way into the mainstream, although the word piezoelectricity is rarely used. But think of the ceramic ignition system that replaced the pilot light in the furnace in your basement. And the water heater that stands nearby.

Vipulanandan simply wired his new cement containing piezoresistive materials to a datalogger so that operating personnel are immediately alerted to any changes. And that’s how the concept of piezoelectricity could be utilized by the construction industry.

The industry already uses sensors, of course. But this new cement could make them cheaper and easier to use in the many millions of dollars’ worth of infrastructure that needs regular inspection, maintenance and repair. Pipelines come to mind as an example. As more oil pipelines are being proposed, and as the public becomes more suspicious of them, piezoresistive sensors could be invaluable. They would be able alert operating personnel of impending problems early enough to prevent a rupture that might pour contaminating oil into the environment.

On the subject of environmental concerns, there is word out of Germany, where Fraunhofer Institute for Wood Research, has had promising early results in the development of new insulating foam materials derived from wood. Most foam insulation is made from plastics derived from oil or gas. But the wood-based foams are natural products made from sustainable raw materials.

Scientists produce the foam by first grinding wood very finely until the tiny wood particles become a viscous mass. Then they add a gas to expand it into a frothy foam. Then they let it harden. The resulting wood foam can be formed into rigid boards or flexible sheets. Like other wood-based products, it can be easily sawed or cut to the desired dimensions.

Fraunhofer believes the material will find a market in home insulation because their product won’t tend to collapse gradually under its own weight, as some existing wood-based insulation materials can do. Researchers are now trying out various species of trees to determine which are best. And they are also trying the best production processes.

They say commercialization is still a few years away.

Korky Koroluk is an Ottawa-based freelance writer. Send comments to editor@dailycommercialnews.com.