Facing the Future
A light-rail transit station in Calgary, Alberta, (above) and face sculptures adorning a condominium complex in Vancouver, British Columbia, (below) are made from new high-tech concrete materials.
For instance, consider some of the new materials developed by concrete giant Lafarge, headquartered in Paris. “Governments are finding they’re having to spend more and more on maintaining their infrastructure,” says Vic Perry of Lafarge North America. “That means you need to build things that last longer and are cheaper to maintain.” He’s talking about big things: bridges, highways, and buildings.
Perry leads the company’s North American operation producing Ductal, one of Lafarge’s newest concrete products. Unlike regular concrete, which is brittle and can rupture suddenly under a heavy load, Ductal can bend. “It will deflect and show signs of cracking before it fails,” says Perry. “You can see in advance that you’ve got a problem.”
What’s more, Ductal is five times as strong as regular concrete. That extra oomph comes from the addition of small fibers dispersed throughout the matrix. These fibers, made of either steel or polymer, reinforce the concrete and eliminate the need for reinforcing steel bars, or rebar. A bridge made out of Ductal can be lighter and thinner than a traditional bridge, Perry says.
Eliminating the need for steel bars has other advantages, including lengthening the lifetime of structures. Consider the deck of a bridge. In the winter, when ice-clearing salt dissolves and seeps into the concrete, it corrodes the steel. The corrosion causes the concrete to detach itself from the reinforcing metal and to crack. A conventional concrete deck needs major repairs or reconstruction after about 25 years, says Perry. “A Ductal deck should last at least twice as long,” he adds.
The material has already found its way into several pedestrian bridges around the world, as well as a light rail transit station in Calgary, Alberta. The canopies that form the roof over the station’s platform and the roof’s support columns are made entirely of Ductal. The canopies provide protection from the elements, can withstand high winds, and support heavy snow loads.
The labor market is another driving force behind concrete innovations. Many people in the industry are anticipating or already witnessing a shortage of laborers who mix, pour, and otherwise work with concrete. The average age of these workers is increasing as few young people enter the field. “So, you have to look at new methods and materials to reduce the amount of labor needed to build things,” says Perry.
In response to this concern, Lafarge has developed Agilia. According to the company, laying a 60-cubic-meter slab of regular concrete—enough for a floor in an office building—requires eight people and takes about 8 hours. Placing the same-size slab of Agilia could require as few as two people and take a couple of hours.
Normally, after concrete is poured, the mason passes a vibrating machine over the surface to squeeze out all the air bubbles. It’s a loud and time-consuming process. However, Agilia contains a mix of additives: superplasticizers that keep the concrete fluid and other chemicals that cut down on the water needed. These enable the concrete to consolidate under its own weight without mechanical vibration.
Because the self-consolidating concrete flows when poured, it can fill intricate molds and wrap around complex structures all the while leaving a smooth finish. The increased fluidity also makes the material ideal for construction in areas of high seismic activity, where structures usually are heavily reinforced with rebar, says Jack Holley, vice president for new product development at Lafarge North America. Trying to use vibration to consolidate standard concrete riddled with a mesh of rebar can be awkward, if not impossible, he says.
To Be Continued…