Hot concrete trends

Some may think a conversation about concrete would be as gray as the cured product. On the contrary. Industry watchers predict coming advances – and challenges – that could change how we use concrete in the not-so-distant future.

Contractor Tools and Supplies editors asked leading industry watchers to comment on several trends in the concrete industry. Here’s what we found out:

Greenhouse gas concerns
As the world gets more concerned about climate change and man’s role in it, investigators are hot on the trail of carbon dioxide emission sources. Cement production is a significant source of carbon dioxide, says Ed Sullivan, chief economist at the Portland Cement Association.

“For every ton of cement produced, there is a ton of carbon dioxide created. Producers may be reluctant to build $.5 billion plants in countries with restrictive taxes or regulations. In the United States, concrete could become yet another imported product, which makes its availability subject to international and political whims and increased costs of shipping. This will be a very interesting topic in the future,” he says.
Self-consolidating concrete

Self-consolidating concrete can flow and consolidate under its own weight, yet is cohesive enough to fill spaces of any size and shape without segregation or bleeding.

“It’s an attractive mix for heavily reinforced concrete or complicated formwork. It has become a constant in the pre-cast concrete market, but has much lower use in ready-mixed concrete,” says Steve Kosmatka, Portland Cement Association (PCA) vice president of research and technical services.

Although less labor is required during placement, it requires more training and experience. “Temperature, humidity, aggregate moisture and mix must be closely monitored. It needs attention and experience all the way to the site,” he says.

Pervious concrete
“Pervious concrete is taking the country by storm,” says Kosmatka. This mix allows water to penetrate it so site designers can better manage surface runoff. Once thought only suitable for areas with above-freezing temperatures, its use is creeping far north of the frost line. Made up of cement, narrowly graded coarse aggregate and little or no fine aggregate, this mix has a low water-cement ratio. Most common applications include use in hydraulic structures as a drainage media, parking lots, pavements and airport runways. It can also be used as a no-fines mix in building walls. The air voids create thermal insulation, cutting heating and cooling costs. Mix designs are still under development and ASTM is developing test methods for pervious concrete, Kosmatka says.

See-through concrete
You don’t have to have X-ray vision to see through concrete any more. Luccon, a brand of translucent concrete, is a fine-grained concrete and translucent fabric cast layer-by-layer in prefabricated molds.
“Luccon uses a special textile made from light-conducting fibers,” says Jürgen Halm, exotic concrete applications and processes specialist at Heidelberg Cement. The translucent concrete is comparable to that of high-strength concrete.

Reactive powder concrete
Stronger and lighter concrete means longer bridge spans, taller buildings and shapes that one wouldn’t think could be made out of concrete, but that’s what’s possible with reactive powder concrete, says Kosmatka. “It’s a patented process that LaFarge has developed and goes by the brand name Ductal. It’s a real paradigm shift for concrete. It can even be made into tubes like a metal.

“It’s a very futuristic product and not a part of any code, so its potential is yet to be seen,” says Kosmatka. “It’s made up of very fine sand and an admixture – there are no other aggregates in it.” The compressive strength of these mixes are as much as 30,000 psi, which means they offer promise in longer bridge spans and in thin-shell, yet strong, concrete components.

Decorative concrete
Stained, stamped or colored, decorative concrete has become a highly designed – and highly profitable – process that turns simple gray concrete into an eye-catching architectural finish.

First used on flat work, concrete stamping and coloring was used to create faux finishes that made the concrete more attractive, says Jamie Farny, PCA program manager for masonry and special products. “Pavement printing has really grown into an art form,” Farny says. It’s also gaining popularity on interior floors.

Stamping requires placing a rubber mat on or taking a rubber roller over curing concrete to imprint a pattern. Colored concrete, on the other hand, can be accomplished with a dry-shake material that’s worked into the concrete surface with a trowel, or by staining it with a chemically reactive stain that penetrates the concrete. Due to concrete pH variation, stain may not take uniformly.

Dyes and tints do not chemically react with concrete but can be applied and then sealed with a clear sealer. Colored waxes can also be used to enhance the look of dyes and tints, but need to be reapplied.

Stencils can be laid on concrete, followed by pass of a sand or grit blaster for a decorative effect.

Farny suggests contractors, designers and owners involved with any decorative concrete decision look closely at samples. “There can be variations in the finish and everyone involved must be aware of it,” Farny says.

AAC/ACC masonry
Autoclaved aerated concrete (AAC) or autoclaved cellular concrete (ACC) is a new form of masonry that is fire-resistant and can be worked with hand tools like a saw and hammer. It is available in block units, large blocks and panels with or without reinforcement, says Farny. Foundation loads are reduced so smaller, less expensive foundations may be used. “It’s recognized by codes and is becoming more viable as a building material,” Farny says.

LEED in concrete
David Shepherd, PCA’s director of sustainable development says Leadership in Energy and Environmental Design (LEED), is gaining interest to help today’s construction be more “green.”

“Recycling is a natural fit for concrete construction. Contractors can use manufactured concrete products that are made with byproducts such as foundry sands.

“We don’t use much recycled concrete as an aggregate source in the U.S.,” he says. “Overseas, this is done quite a bit, especially in resource-limited countries like Japan and England. It’s not done here because we are not resource-limited, but it can certainly help drive sustainability.”

Information technology
Technology for concrete construction has advanced greatly, but Building Information Modeling (BIM) is one that will change commercial construction dramatically. The industrial sector has employed BIM for more than 20 years to build industrial plants and it is now taking off in commercial construction.

BIM software eliminates wasted labor from the construction process by modeling the building before construction and uncovers potential conflicts between mechanical, electrical, plumbing and framing work.

“The contractor can employ BIM to save money by speeding construction, sequencing the work and expediting the procurement schedule,” says Iyad Alsamsam, general manager of StructurePoint, a provider of software and technical resources for civil and structural engineers. “That represents dollars direct to the bottom line.”

Published in the January/February 2008 issue of Contractor Tools and Supplies magazine.

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