We here at Spectrum have been busy researching Photo Catalytic Concrete to help improve build our skateparks Eco-Smart. As concrete is used for many other things besides building skateparks, we thought we should share our research with everyone else out in BuildingGreen land. Enjoy!
Photo-Catalytic Concrete
1. “A Concrete Step toward Cleaner Air” by Bruno Giussani, article on InnoEurope website:
http://innoeurope2.cma.ee/index.php?lang=eng&main_id=16&id=121
- Italian Pavilion in Venice Biennale incorporated this product. Parts of the concrete walls and grounds have been built with cement containing an active agent that, in presence of light, breaks down air pollutants such as carbon monoxide, nitrogen oxide, benzene, and others through a natural chemical process called photo catalysis.
- The technology, called TX Active, has been under development for almost 10 years in the labs of Italcementi, and is starting to be applied commercially to buildings and streets in Italy, France, Belgium, and elsewhere.
- A street in the town of Segrate, near Milan, with an average traffic of 1,000 cars per hour, has been repaved with the compound, "and we have measured a reduction in nitric oxides of around 60%,"
- Active principle in TX Active is a blend of titanium dioxide that acts as a photo catalyser—can be incorporated in cement, mortar, paints, and plaster.
- In the presence of light, speeds up the natural oxidation processes that cause the decomposition of pollutants, transforming them into less harmful compounds such as water, nitrates, or carbon dioxide.
- In Italy, the product is also known as "cemento mangiasmog" or "smog-eating cement".
- It does costs more than typical cement, but active principle only need to be used on the surface.
- "To transform the facade of a five-story building into a photo catalytic surface would add only 100 or so euros ($120) to the cost of a traditional paint or plaster".
- Photo catalytic blocks cost about one-third more than usual paving.
- Used in Richard Meier’s Dives in Misericordia church in Rome (2003), also Air France headquarters inside Charles de Gaulle airport in Paris.
- Architects/ designers like it because it stays white, thus an aesthetic benefit.
2. Photo catalysis Background Info.
http://dev.nsta.org/evwebs/1952/photocatalysis.htm
- Photo catalysis is a reaction which uses light to activate a substance which modifies the rate of a chemical reaction without being involved itself.
- Semiconductors are what are usually used for this.
- Chemically speaking: “…semiconductors are usually selected as photo catalysts, because semiconductors have a narrow gap between the valence and conduction bands. In order for photo catalysis to proceed, the semiconductors need to absorb energy equal to or more than its energy gap. This movement of electrons forms e-/h+ or negatively charged electron/positively charged hole pairs. The hole can oxidize donor molecules…”
- Titanium Dioxide (TiO2) is used because:
-inert
-resists corrosion
-inexpensive
-can react in mild operating conditions
- However, needs UV light for photo catalysis to occur.
3. TX Active - Photo catalytic cement technology.
This is the specific product line, available in North America through Essroc Cement Corp (www.essroc.com)
http://www.essroc.com/default.aspx?pageid=216
TX Active line has 2 products:
1. TX Arca cement, concrete with self-cleaning benefit. Photo catalysis reduces maintenance by destroying most organic/inorganic pollutants that contact concrete and cause discoloration.
2. TX Aria cement, has added ability to mitigate environmental pollution. Effectively destroys airborne pollutants, which are responsible for urban organic pollution.
- How do they work? Products use hydraulic binder with photo catalytic properties.
- Developed over a decade’s R&D by Italcementi’s Technical Research Center in Bergamo, Italy.
- TX Active concrete can be used in vertical, horizontal, structural, architectural pre-cast, plaster and coatings, concrete blocks, jersey barriers, retaining walls, concrete paving and cementitious tiles.
- Photo catalysis also has antibacterial benefits.
4. Concrete That Cleans Air, blog entry on Shawn Hogan fan club blog.
http://www.shawnhogan.com/2006/11/concrete-that-cleans-air.html
- “The results so far are astonishing: A street in the town of Segrate, near Milan, with an average traffic of 1,000 cars per hour, has been repaved with the compound, "and we have measured a reduction in nitric oxides of around 60%," says Italcementi's spokesperson Alberto Ghisalberti. In a test over an 8,000 square meter (or approximately 2 acres) industrial area paved with active blocks near Bergamo, Italcementi's hometown, the reduction was measured at 45%. “
- “In large cities such as Milan, with persistent pollution problems caused by car emissions, smoke from heating systems, and industrial activities, both the company and outside experts estimate that covering 15% of all visible urban surfaces (painting the walls, repaving the roads) with products containing TX Active could abate pollution by up to 50%, depending on the specific atmospheric conditions. „
4. Air-Cleaning Concrete –
http://www.sciencenews.org/articles/20050101/bob9.asp
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