Fashion eco - that is not all gold that glitters

In recent years, it is gaining popularity, somewhat rightly, ecology. Ecology is a cure for all evils of this world, an essential addition wherever necessary (but also where unnecessary), or where the chance of meeting certain assumptions is really small. This trend has also been touched and construction, and with it, and binding materials, namely - cement

The slogan "eco" is normally one of the three main roads of advertising:

• both products are old (the base and the added), but has been found for one or both of these new applications
  
• a product is new and one old - therefore to achieve a completely new possibilities for action
  
• both are new, and both of them come to a completely new areas undeveloped by the existing products on the market
  

In the case discussed here this is that first option. Both products, namely cement and additive - compound dioxide titanium (TiO₂), have long been known. The latter was known until now as a pigment and such was its use. The occurrence, method of production, possible errors in production and know how to avoid them - it was all familiar. Also it, the possibilities of a pigment, how stains, what is its chemical stability, shelf life and so on.

They tested him again and discovered that among the various interesting property has at least two, if not that will revolutionize the construction industry, at least allow him a big leap forward. These are:

• ability to decompose nitrogen oxides and others into less harmful compounds under the influence of solar radiation, wherein the compound (TiO₂) itself does not fall apart, but rather a catalyst almost indestructible
  
• the ability to reduce the surface tension of this dirt and impurities deposited on it, that even a small rain rinse them with no problem
  

This meant that, among others, building can play an important ecological role by reducing the emission of dangerous gases, and helping to keep clean facades or concrete structures reduces the consumption of detergents used to clean them (which takes place depending on the position every few years time).

Unfortunately, the reality turned out to be much more complicated, and this "eco" much exaggerated. Let's start ...at the end

The surface to call it "self-cleaning" filter is necessary (that is just a thin coating) of TiO₂ applied to the material. During laboratory tests it turned out that not enough that the filter must be applied at a relatively high temperature, it must be fairly accurately determined - in this case approx. 400C - that this filter is best fulfilled its role. The imposition of such a filter on the glass (which melting temperature is above 1000C) or brick (here burning well at a temperature of more than 800C) is not a problem – bigger troubles could made surface of the material that may affect the behavior of such a filter during application, or chemical compounds contained in such product.

The question on the cement or concrete or mortar precisely-made on its basis is one thing - how to apply the filter at a temperature of several hundred degrees to its shell was a whole and fulfill your role? Individual concrete elements - already sooner, but it is still tedious and expensive process, which in principle are excluded mortar, because I like to make ...

Another problem is that the "clear" the distribution of titanium dioxide and other nitrogen compounds takes place under the influence of UV radiation. It is very important that due to the Earth's atmosphere and the geographical location of the amount of radiation that reaches the surface is approx. 4%. Adding to this the fact that another approx. 4-5% is called. close to visible light UV can be easily said that these capabilities are very, very limited. As part of the work on this subject can be read that the yield is approx. 10-15% of that reached by the TiO₂ under UV light. It is not much, even very little.

Bring slowly effects of ongoing laboratory research aimed to change these proportions. The problem is only these modifications and additions, which sometimes reach even 20% pure substance. Among them they are Precious metals (gold, silver) or sulfur-based compounds

Cement because of the function and the role it plays should have as little additives in their composition, which are converted for clinker. It is one thing to add quartz dust or sand quartz already during the manufacturing process of the concrete or concrete mortar, and then adding the other ingredients in the production of cement alone.This means that the concrete to fulfill its role, it will need to develop research as much, when and how the compounds added to the titanium dioxide in order to change its properties desired for us direction (ie activity in visible light) will affect everything from such a cement is formed.

In addition, it appears that the compounds of the TiO₂ under the influence of the modification over time lose its properties, and studies indicate that after six months of falling into 1/5 of the initial value - a lot, especially the white cements generally have a relatively long shelf-life of typically exactly half a year, sometimes more – a year…..

Another problem arising with the same material, for which it is to be added or titanium dioxide is its quantity. It is generally accepted that the maximum amount of pigment (or the compounds do not participate in the bonding process) added to the cement in the concrete or mortar kneading usually not exceed 5%. Due to the fact that the white cements are a class of (usually) 52.5 - the amount may be increased by an additional 1-2%. This means that the amount of TiO₂ in cement can not or otherwise - should not, not exceed 2% relative to the quantity of cement to be able to add other additives (eg. pigments) having to affect, in one way or another to the mixture.

Operation of the titanium dioxide is surface - which means that the TiO₂ will be located deeper - does not take any part, that either we accept the fact that this small amount of really major part shall not in any way participate or be used another much more complicated technological process, which will allow the use of cement with substance only as a thin face ... and it is not only difficult, but also compliance with the construction, in many cases impossible. Artificial stone or terrazzo must have a minimum thickness of 25 mm, and the minimum thickness of the top layer of restoration render is 10 mm ...

Mindful also of the fact that these trace percentages in the visible light works only 10-15% of cement and TiO₂ that the best method of imposing the filter is to apply it at a temperature of about 400C - a symbol of eco and environmental impact of buildings with cement or plaster or mortar, where it was used, in principle, if not none, it is at the moment negligible.

In the present conditions, the addition of TiO₂ does not make it will be eco-cement or eco-technology, or even the proverbial gold. This is the only information that somewhere far away, at the end of a very long road might be something that could be useful in the construction industry, and it will be applied to the cement without any concerns about the quality of the products produced from it. This also means that it will be known to any possible constraints that TiO₂ brings.