TEMPLE OF NANOSCIENCE Rome’s Dio Padre Misericordioso Church, also known as the Jubilee Church, retains its bright white color because of nanostructured titanium dioxide.
Chemical and Engineering News – Nanotechnology makes inroads in the construction industry Completed in 2003, the Jubilee Church, is a flagship when it comes to the use of nanotechnology in construction . Nanostructured TiO2 particles theoretically will keep the concrete white forever, even in smoggy Rome. But there are more humble examples, too. Whether it’s in steel, concrete, or windows, nanotechnology is finding a growing number of applications in the construction industry, where it promises to make structures that last for centuries and look as clean as the day they were built.
When ultraviolet light strikes the anatase form of TiO2, it excites the material so that it becomes a catalyst for oxidizing organic grime.
And the concrete doesn’t just resist smog, it eats smog. The same photocatalytic chemistry that keeps the church clean also cleans the air around it, gobbling up NOx, SOx, carbon monoxide, aromatics, ammonia, and aldehydes. Italcementi estimates that if it covered 15% of the visible surfaces of a large urban area, such as Milan, with its current product containing the smog-eating nanostructured substance, TX Active, it could cut the city’s air pollution in half. It’s important that the material be nanostructured to have a high surface area in the cement application. The material used in Italcementi’s cement has more than 200 m2 of surface area per gram.
The level of investment in construction research is very low.
One area in which Shah’s group (Surendra P. Shah, a civil engineering professor at Northwestern University and the former director of the school’s Center for Advanced Cement-Based Materials) has been conducting research is using carbon nanotubes and nanofibers to reinforce cement and concrete. “When you see cement and concrete, you see cracks because it’s a brittle material,” he explains. “These cracks start at the nanoscale. We have shown that once you know how to disperse them, very small amounts of carbon nanotubes, such as 0.05%, can substantially increase the cracking resistance.”
BASF also makes a whole line of additives bearing the nano moniker, including Nanocrete, Nanoflott, Nanolight, and Nanosilent. These products don’t contain nanoparticles, Christensen explains; rather, they form nanostructures as they’re used
BASF’s use of nanotechnology in construction materials isn’t limited to cementitious products. They also make Col.9, a dispersion of organic plastic polymer particles and nanoscale particles of silica, which is used as a binder to produce façade paints. According to the company, this combination of elastic organic material and hard mineral resists cracking in cold temperatures but doesn’t become tacky when it’s hot outside.
The nanoparticles in Col.9 are also hydrophilic, spreading rainwater across the surface of the coated area. During heavy rain, this property helps the coated surface wash away dirt, and after the rain, it disperses any remaining water into a thin film that dries quickly, thereby preventing mold.
Another nanostructured building product that’s on the market is a type of steel, known as MMFX 2, developed by MMFX Technologies. Its inventor, University of California, Berkeley, materials science professor Gareth Thomas, first used electron microscopy to peer into steel’s nanostructure in the 1980s. Twenty years later, Thomas led MMFX in developing a series of key patents for making nanostructured steel.
MMFX 2 steel is made with conventional steel-making equipment. They make MMFX 2 steel at 100 tons an hour. The material has been used in buildings, highways, and bridges and has an expected service life of 200 years. And because it’s twice as strong as conventional steel, Pollack notes, structures require less steel to do the same job. So although the steel itself is more expensive than conventional material, labor costs are reduced.
Adding a nanoscale coating of TiO2 to glass, companies make low-maintenance windows that can clean themselves.
Nanoscale sensors are starting to be embedded within a structure’s foundation and could “give you early warnings if you need to do something about a bridge or a building,” Alvarez says.