Self-cleaning cement
To a greater or lesser extent, we all strive to preserve our appearance, and sometimes we even try to disguise the traces that the passage of time creates in us. It is clear that the value of aesthetics is given
importance. Buildings also suffer from the passage of time. When they are newly built, they remain clean, bright and slender, but as the years go by, they age, darken and often don’t look good. To address this problem, Cementos Rezola has created a new product: self-cleaning cement.
Cement, in keeping with fashion, is also in search of constant youth and
beauty. We’ve often noticed that buildings, when they’re freshly made, have a beautiful blindness, but in a few years, most of them have lost their brightness and are no longer as eye-catching. The materials age and, above all, become soiled. The main
source of this dirt or contamination is human activity. Combustion engine vehicles, industry, thermal power plants, household heating and various agricultural farms are the main sources of pollution. As a result, sulfur dioxide, nitrogen oxides, and carbon monoxide, for example, are present in the atmosphere more than desired. And by reacting them together, ozone, benzene, nitrogen dioxide, acidic substances, etc. are formed. Many of them accumulate on the surface of buildings together with moss, lichens and dust particles of all kinds. Ten years ago, the
Italcementi group set out on the road to self-cleaning concrete, together with a number of public and private organisations from all over Europe.
Jabier Barrenetxea; Cementos Rezola. These mentioned pollutants accumulate in buildings, but actually degrade in a
natural way. Sunlight and ultraviolet light initiate oxidation-reduction reactions; as a result, many organic substances are dissolved. A well-known example is that of plastics: if you spend a lot of time in the sun, a lot of plastic ages, stiffens and becomes brittle. This oxidation process, however, is very slow and, in most cases, the accumulation of contaminants is faster than degradation. But if
a catalyst is used, the reactions can be accelerated, and this is what the Italcementians have done: to get rid of the pollution that accumulates on the concrete, they have used a photocatalyst. That is, the concrete has been mixed with the substance that accelerates oxidation by the action of light.
Jabier Barrenetxea; Cementos Rezola. Italcementi GroupFrom the
beginning they focused on titanium oxide. In fact, titanium oxide is already used in the form of white pigments in paints, plastics, cosmetics, etc. And self-cleaning is also used in glass in the past. However, titanium
oxide cannot be used as such and they have had to look for the right variant and then ensure that it has the right results when incorporated into concrete. To this end, the effect of
the photocatalyst has been measured in the laboratory. For example, ordinary concrete and photocatalyst have been stained with rhodamine dyes. having been exposed to light for about 30 hours, the color of the concrete with photocatalyst is almost the same as
that of unstained concrete. But it has been found that concrete with photocatalysts is capable of self-cleaning as well as cleaning the surrounding air.
Jabier Barrenetxea; Cementos Rezola. At the Italcementi Group
Laboratory, such experiments have been carried out with closed chambers. The degree to which the concentration of nitrogen oxide decreases in one has been measured.
A nitrogen reduction of up to 91% has been measured with concrete with photocatalysts in the best conditions, just 6 hours after the start of the experiment. In yet another chamber, atmospheric air has been passed over the pieces of concrete containing the photocatalyst and the exhaled air contains only 30% of the introduced contaminants. With decent results in the laboratory, the
following tests have been carried out outdoors. Containerized trucks have been used to simulate street conditions, alongside CGT laboratories in France. Two streets have been used, one of which has covered the walls with conventional concrete; the other with concrete with photocatalyst. In both of them, a tube has been installed that emits the smoke of an engine, as well as instruments for measuring nitrogen, organic components and climatological data. The results have been very variable, depending on wind, humidity, number of particles in the air and other variables. However, it has been measured that up to 200 cubic meters of air can be cleaned per square meter of concrete with
photocatalysts. Finally, pavement pieces have been installed on the streets of Segrate and Caluso in Italy and the results have been repeated.
Jabier Barrenetxea; Cementos Rezola. Italcementi GroupIt is a
new product that was launched last year in France and Italy and this year in Spain. However, there are half a dozen buildings made with Tx Active concrete since 2000 and, for the moment, they maintain their original color thanks to the photocatalyst incorporated in the concrete plates on the outside of the building. The truth is that, given its characteristics, the new product can serve to combat environmental pollution in addition to cleaning the buildings themselves, but the truth is that the use that has been given to it so far has
been mainly aesthetic.
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