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EU smart construction materials absorb and wash away pollution

March 04, 2004

A European consortium of private enterprises, research institutions and the European Commission's Joint Research Centre (JRC) is running a test programme for innovative construction materials set to help in the fight against air pollution. The "smart" construction materials (plaster, mortar, architectural concrete) and coatings are being developed as part of the PICADA (Photo-catalytic Innovative Coverings Applications for De-pollution Assessment) project. Special construction materials and coatings containing titanium dioxide (TiO2) can "capture" and "munch" organic and inorganic air pollutants after they have been exposed to ultra-violet and/or sun rays. The "degraded" polluting substances can then be washed away by rainwater. The new construction materials should help to reduce levels of nitrogen oxides (NOx gases) which cause respiratory problems and trigger smog production, and of other toxic substances such as benzene. The whole project will cost EUR3.4 million and the European Commission is funding up to EUR1.9 million.

"Smart coatings can cause a revolution, not only in the management of air pollution but also in how architects and town planners tackle the persistent problem of urban smog," says European Research Commissioner, Philippe Busquin. "The PICADA project itself is closely linked to the remit of our programme for competitive and sustainable growth, and fosters strong collaborative ties with various different European businesses."

The European Commission contribution

Various types of "smart" construction materials were tested under experimental conditions of humidity, temperature and ultra-violet (UV) radiation at the INDOORTRON facility at the Commission's Joint Research Centre (JRC) in Ispra (Italy), simulating a real world setting. NOx gases and organic compounds diffuse through the porous surface and stick to the titanium dioxide nano-particles of the construction materials and coatings. Absorption of UV light by the incorporated TiO2 leads to its "photo-activation" and the subsequent degradation of the pollutants absorbed onto the particles. The acidic products created by this process are washed away by rain and/or neutralized by alkaline calcium carbonate contained in the materials.

Cementing future potential

The innovative materials developed by the consortium have yet to be applied outside of laboratory testing conditions. Preliminary tests, however, with similar photo-catalytic materials under field conditions show that air quality can be significantly improved. In 2002, after 7000 square metres of road surface in Milan, Italy, were covered with a photo-catalytic cement-like material, there was up to 60% reduction in the concentration of nitrogen oxides at street level.

Similarly, measures taken in Japan using photo-catalytic cements and paving slabs show a marked decline in air pollution. Coating materials designed on the basis of titanium oxide are better because they can cover a much greater surface than cement, since buildings and street furniture can be covered or painted with them.

Succeeding where other coatings failed

The de-pollution properties of these materials are based on the semi-conducting photo-catalytic titanium dioxide (TiO2). The coatings containing TiO2 are effective because air turbulence constantly carries NOx and other volatile and semi-volatile compounds over the surface of the buildings; the molecules stick to the surface long enough for the oxidation process to break them down.

The PICADA project at work

The PICADA Project, (Photocatalytic Innovative Coverings Applications for Depollution Assessment), began on January 1, 2002 and will finish in 2005.

The main project objectives are:

- A better understanding of the processes and chemical mechanisms
- Assessment of the cost and durability performances of the coverings
- Product development and marketing

Currently, several photo-catalytic processes using the new materials and coatings are being studied at the INDOORTRON facility. Here EU scientists will measure the efficiency of the coatings in breaking down mixtures of pollutants (NOx and aromatic compounds), which greatly contribute to the formation of smog.

Targeting NOx gases and indoor air pollutants

These new construction materials and coatings will be instrumental in helping meet the EU target of reducing NOx levels to under 21 parts per billion per year by 2010. Up until now EU researchers have focused on the development of innovative materials for outdoor applications. In future, particular attention will be paid to investigating whether these products can be used as de-polluting building materials and coatings in indoor environments, too.

European Commission, Joint Research Centre (JRC)