Repsol YPF

With the passing of time, building façades tend to become increasingly dirty, which results in a significantly deteriorated appearance and a laborious and costly cleaning process when the building's appearance becomes unacceptable. 

Meanwhile, the cloud of pollution that hangs threateningly above big cities, noticeable at a glance in places such as Madrid and Barcelona, represents a serious public health issue since it spreads respiratory diseases such as asthma and lung cancer. 

European research

Incorporating the solution to both issues in a building material, or at least the best way of mitigating them, has been the subject of research by several laboratories in a project sponsored by the EU. This is the PICADA project (Photo-catalytic Innovative Coverings Applications for D-pollution Assessment).

This project brings together a European consortium made up of private research companies and institutions, and the European Commission’s Joint Research Centre (JRC) which has been developing products  to achieve these objectives for several years. 

What does it involve?

To a certain extent, the self-cleaning and decontaminating function of the materials  researched will be similar to the plant photosynthesis process. When exposed to sunlight, certain building materials and special coatings containing titanium dioxide can decompose, through oxidation, various atmospheric pollutants. Subsequently, the rainwater takes care of removing the product of this chemical process, known as photocatalysis, from the façade. 

The materials researched include some which are as common as plaster, but the most promising result is that of Tx Active. This is a kind of cement that has recently been marketed by one of the companies participating in the PICADA project. One of the experiments carried out during the investigation was to cover seven kilometres of a road in Milan with this material. The result could not have been more promising: a reduction of up to 60% in the nitrous oxide concentration at street level was recorded. 

In line with other similar experiments, it is considered that its capacity to reduce pollutants is between 20% and 80% of the total, varying depending on the atmospheric conditions and the solar radiation. That way, if a city were to cover 15% of the visible surface with products containing Tx Active, it is estimated that this could halve the pollution. 

Present and future 

In fact, this type of cement has already been used on emblematic buildings such as the “Dives in Misericordia” basilica in Rome, the “Hotel de Police” in Bordeaux and the new Air France head office at the Roissy-Charles de Gaulle airport in Paris. Naturally, as is to be expected, this material also has some disadvantages, mainly its high cost. Its cost is at least six times higher than that of conventional cement.

Although it must be taken into account that it must only be applied to the outermost layer of the façade, such that the total increase in construction costs will be barely 1%. As such, it is reasonable to expect that its use will gradually become more widespread and that all buildings will use it in the near future.  

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