Simix listed in The Journal of Architectural Coatings’ 2009 Top Green Coatings Picks (JAC,
A number of effective “low-tech” antimicrobial strategies can
also be found in coatings applications. Simix Solutions uses a
combined approach to exterior surface treatment in its NP Self
Cleaning Technology products; one such product, Oxi Seal concrete
and paver sealer, was used to protect outdoor school
areas against mildew in a project highlighted in the Journal of
While the product does utilize nano TiO2, additional antimicrobial
action derives from the formulation’s highly alkaline
potassium silicate base, as microbes cannot live on surfaces
with a pH level above 9.5. Since a traditional polymer resin
base is not part of the product formula, the issue of photocatalytic
degradation of coating binder is avoided.
Smog-Eating Concrete Tested In MissouriSheryl S. Jackson
Smog-Eating Concrete Tested In Missouri Sheryl S. Jackson
Project explores sustainability of three emerging technologies.
Although “smog-eating concrete” sounds like a plot for a strange science fiction movie, it is not only reality, but is a technology used on a highway project in the United States.
As part of the Missouri Department of Transportation’s (MoDOT) efforts to construct pavements to meet sustainability goals, the agency has teamed up with the National Concrete Pavement Technology Center (CP Tech Center) and cement manufacturers, Essroc Italcementi Group, and Lehigh Hanson, Inc., to research new pollution and water quality control technology. Representatives of the Federal Highway Administration and the U.S. Environmental Protection Agency also serve on the project’s steering committee.
The highway test section on Route 141 near St. Louis was constructed with concrete containing an innovative cement product blended with photo-chemicallyactive titanium dioxide (TiO2). Known as TX Active™, the product produces a self-cleaning and pollution-reducing concrete.
Originally developed by Essroc Italcementi Group in 1996 to meet the specifications required by the architect of a church in Rome, Italy, the cement has been used in a variety of concrete applications, says Dan Schaffer, product manager of TX Active for Essroc. “The original request was for a self-cleaning concrete so the exterior of the church would remain white, even though it was in a very polluted area,”He explains.
Sunlight triggers the photocatalysts in the product that speed up the rate of the natural oxidation process that decomposes some organic and inorganic substances on the surface and in the atmosphere.Researchers discovered that not only does the product keep the surface clean by destroying pollutants on the surface before they could build up, but it also improves air quality by breaking up the pollutants into harmless substances.
“The PICADA Project [Photocatalytic Innovative Covering Applications for De-Pollution Assessment, www.picadaproject. com] studied the pollution reduction effect of the product in Italy and France between 2001 and 2005,” says Schaffer. Essroc began distributing the product in the United States in 2007. “The first U.S. uses have been in architectural precast panels and interlocking concrete pavers. The Missouri project is the first use in highway pavement,” he adds.
“The TX Active cement was brought to our attention by MoDOT and they asked if this was something we could incorporate in a project,” says Todd LaTorella, P.E., executive director of the Missouri/Kansas Chapter of the American Concrete Pavement Association. LaTorella contacted Essroc and arranged a meeting with MoDOT representatives to discuss the product and identify an appropriate project for a demonstration.
“After some discussion we determined that it would be best to use the product on a high-traffic roadway in a metropolitan area to demonstrate its effectiveness in reducing environmental pollution resulting from vehicle traffic,” he explains.“MoDOT’s Green Road Initiative Project on Route 141 and TX Active seemed to be a great fit.”
About the Route 141 Project
A 1,500-foot, three-lane TX Active test section of Route 141 near St. Louis is part of a highway improvement project that will expand the current two-lane highway to six lanes that are raised above flood level, says Jesse Jonas, P.E., Resident Engineer in the Chesterfield Project Office of MoDOT.
In addition to testing the pollution control properties of the photocatalytic cement, the project is being used to evaluate the use of two-lift construction as a way to control costs of the new technology. The project also is being used to evaluate the effect of pervious concrete on stormwater runoff, and more specifically, the technology is used in a roadway shoulder application.
The photocatalytic concrete is the common denominator in both the two-lift mainline pavement and the pervious concrete shoulder. This combination of technologies is said to represent one of the most technically advanced and environmentally- friendly concrete pavement systems ever employed.
Two-lift construction is important for the use of TX Active, says Bill Stone,P. E., MoDOT research administrator. The top, 2-inch lift contains the TX Active,
While the bottom 7-inch lift contains less expensive, conventional paving materials.“Not only does two-lift construction keep material costs lower, but when you have a product that works when exposed to sunlight, it makes sense to only place it at the top of the pavement,” he says.
“Representatives from MoDOT had seen a photocatalytic cement presentation in 2008, and in 2009, we were asked to find a project that could be used to test the product,” says Stone. “The Route 141 project is a relocation of an existing road which makes it ideal to collect baseline research information before the road opens.”
The test section is part of a 2.1-mile project that includes six traffic lanes, eight bridges and two major box culverts.Construction costs for the project are $44.5 million. Although the test section was a two-lift construction, the remainder of the project is a traditional, monolithic pour, says Justin Brooks, P.E., senior project manager at Fred Weber Inc., the contractor for the project. Work on the project is scheduled for completion in July 2012.
“With the road scheduled to open in July of 2012, we’ll have a few months to collect information before it opens to traffic,” says John T. Kevern, Ph.D., LEED AP, CP Tech Center Researcher and Assistant Professor of Civil Engineering, University of Missouri-Kansas City.
The data collected will measure the impact of TX Active on air and water quality by comparing samples collected from the test section that contains TX Active in both the three lanes of trafficbearing roadway and the roadway shoulder with a section that is similarly constructed but has no TX Active in the concrete. “We’ll be able to look at the performance of the photocatalytic product in a variety of temperatures and humidity levels,” Kevern says.
The two-lift construction of a portion of roadway using different mixes of concrete for the test sections required a good bit of planning, Brooks explains.“The two-lift process doesn’t require any special equipment but two pavers and extra manpower are needed, and you have to make sure the correct material goes to each paver,” he says. “We also used two batch plants to produce the material.”
“Two-lift construction is common in Europe but I believe it will become more common in the United States,” says Brooks. Because the lower lift is composed of more economical or recycled materials, Two-lift construction can control the cost of material and create a more environmentally conscious project.
“This was the first time we’ll construct shoulders using pervious concrete,” says Brooks. “It is not something we’d normally do on a heavy roadway.” Although no special equipment is needed, the method for placing the concrete is a little different, he adds. Construction of the traffic lanes for the test section is complete and the shoulders will be poured in spring 2012.
Pervious concrete is more commonly used in parking lots or in specific areas to manage storm water runoff, points out Kevern. By studying its performance and impact on the quality of water in the many streams and creeks along Route 141, pervious concrete’s environmental benefits for highway construction can be evaluated.
“Our goal is to find environmentally sustainable construction techniques that work well, use standard equipment and are cost effective,” Kevern explains. The concrete with the new titanium dioxide additive has an expected lifespan similar to normal concrete.
Although the test section of Route 141 is big enough to quantify the effect of “smog-eating” concrete in reality as opposed to the research lab, this test is not large enough to quantify the cost of using photocatalytic concrete, Kevern says.
“Photocatalytic cement is significantly more expensive than regular cement so I don’t see it in the budget for major pavement construction at this time,” Brooks notes. “The price will probably come down as it is used in more settings, so that along with lower material costs associated with two-lift construction, the cost may eventually become feasible for more highway projects.”
“We know from research in Italy, that we can anticipate a reduction of up to 40 percent in hazardous nitrogen dioxide when the trial period comes to an end,” says Jonas. The Italian research results were obtained in an area in which row houses lined the road and trapped the pollutants more than the open area around Route 141, he points out. “Our results may not be as dramatic because of the two different environments, but we do expect to see a reduction in the pollutants in the area.”
“We will collect data for 18 months,” Kevern says. “I anticipate the release of periodic results throughout 2013, with the formal report released in 2014
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