Across the country, construction teams are turning to concrete innovations to get the job done. New trends are sweeping the industry form Texas, Alabama and Georgia, where the state's DOT recently used roller-compacted concrete for the first time on a highway reconstruction job, to Chicago, Seattle and Monterey Bay, where a school aims to be the first new educational campus to earn a LEED platinum designation using, among other things, ground-granulated blast furnace slag in lieu of Portland cement or flyash.

By Bruce Buckley, Washington D.C. correspondent, Engineering News-Record. The McGraw-Hill Construction publication can be read online by visiting www.enr.construction.com

A construction boom coupled with designers and contractors looking for faster and better ways to deliver projects for owners have created an ideal environment where concrete innovation has thrived in recent years. Although the acceptance of new technology in concrete has traditionally been a slow and methodical process in the United States, market forces have converged to drive the use of more emerging mixes and applications.
As with many building materials, increased construction activity nationwide has spurred greater use of concrete. In 2006, consumption of Portland cement, a main ingredient in concrete, is expected to reach a record 124 million metrics tons - reflecting 2.3 percent growth over 2005, according to the Portland Cement Association. Even as construction activity is predicted to cool this year, the market should record another 1.3 percent gain in 2007.

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Rising costs over the past five years of other building materials, such as steel, have helped contribute to the popularity of concrete. Additionally, durability and speed of delivery have been factors. With owners looking to have projects completed faster, use of precast concrete has risen dramatically. In 2005, use of precast increased by 17.5 percent compared to 2004.
Ty Gable, president of the National Precast Concrete Association, said precast has reached greater popularity as owners request more fast-tracked projects and contractors struggle with labor shortages.
"It's more and more of a challenge on the jobsite to get the skilled labor necessary, so architects and designers are turning to precast to get jobs done faster," he said.
In many cases, they also want them to last longer. Durability has become an increasingly important aspect of the developer's equation on infrastructure projects, especially as more private entities have begun to invest in roads and bridges, said Steve Kosmatka, vice president of research and development at the Portland Cement Association.
"Public-private partnerships create an opportunity for people to use innovations, as opposed to the standard designs that have been in the books for 30 years," he said. "PPPs are willing to take risks especially if they see it reduces maintenance. Banks that look at these projects want technology that will allow contractors to put down a bridge or highway that won't have to be touched for years."
The trend is promoting greater interest in use of ultra-high performance concrete, also known as reactive powder concrete, which is nearly five times stronger than conventional concrete. Although it has been used abroad, researchers are testing it in the U.S., including a new bridge built in Iowa that is the first in the country to use the material.
Michigan's Department of Transportation and University of Michigan scientists are testing the use of a new fiber-reinforced "bendable" concrete, also referred to as engineered cement composites concrete. Because it can bend, ECC reportedly is less likely to crack and fail. It's also nearly 40 percent lighter than conventional concretes.
"Traditionally, DOTs have been conservative - they don't want to take risks," Kosmatka said. "To see them take an interest in doing these things on their own is promising."
Despite early progress, the same barriers to acceptance remain - without broadly recognized specifications and testing methods, limited numbers of engineers will take risks on new materials.
"You can't go to the building codes and find out how to use these materials," Kosmatka said. "The average engineer at the average firm wouldn't know how to use them."
Despite this, the demands of developers often prevail. Pervious concrete has gained tremendous interest among developers as an option for storm water management. Water passes through pervious concrete where it is filtered by the concrete matrix. Using pervious concrete on parking lots could allow developers to avoid dedicating a portion of their site to retention ponds, thereby saving them money on land costs.
Dan Huffman, director of natural resources at the National Ready Mixed Concrete Association, said he hopes that pressure from owners will prompt the industry to embrace pervious concrete.
"Agencies and owners of sizeable companies, such as Wal-Mart, are slobbering over this technology," he said. "We just need to get our act together in terms of having concrete producers who can make the material and contractors that can put it down."
The potential of pervious concrete is one of many ways that concrete is riding the trend toward more environmentally friendly developments. Use of pervious concrete, for example, can be used to gain points toward LEED certification. In some cases, designers are using recycled materials as aggregate in concrete to gain LEED points.
Researchers in Italy are pushing the envelope even further. Italian producer, Italcementi, have produced a so-called "smog-eating concrete." The material contains titanium dioxide, which, when triggered by sunlight, absorbs pollution and releases it as non-toxic gas. As a result, the concrete also stays clean.
While cutting-edge advances could have an impact in the coming decades, many are looking for yesterday's innovations to become the norm. Lionel Lemay, vice president of technical resources at the National Ready Mixed Concrete Association, said he sees self-consolidating concrete, or SCC, as having the greatest room for expansion in the industry. The labor-saving qualities represent a main reason he expects it to gain greater acceptance in the coming years.
"Anything that reduces labor is a positive these days," he said. "If it saves having to put someone out in the field to vibrate the concrete, that's a plus."
The growth in SCC has trended along with increased use of precast concrete. The NRMCA estimates that 40 percent of precasters use SCC. Meanwhile, researchers continue to experiment with new applications for SCC. A project under way at Iowa State University is tackling one of the more challenging potential uses of SCC - paving.
"I believe eventually all concrete could meet the self-consolidating definition," Lemay said. "At some point there will never be a need to vibrate concrete anymore."

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