Civil Engineering Reference
In-Depth Information
effectiveness of photocatalytic properties on a 1 : 5 scale model reproducing
the environmental conditions of a street located between two buildings, in
a generic urban context. Two 18 m long lanes were built, and walls were
covered with normal plaster in one case and photocatalytic plaster in the
other; the atmosphere within the canyons was modifi ed by fl owing engine
exhaust gases. Both air composition and environmental parameters were
monitored, and the effi ciency of photocatalytic plaster in keeping air cleaner
was proved, with an up to fourfold decrease of contaminants compared to
normal plaster in favourable weather conditions (wind, mainly).
Nowadays, examples of TiO
2
-containing building materials can be found
almost anywhere: some of them are just pilot projects, like the 'street
canyon', others are the fi nal product of this technology. One early example
of the use of photocatalytic TiO
2
in the European built environment, and
probably the most renowned, is the already cited church Dives in Miseri-
cordia, designed by Richard Meier and built with precast blocks of photo-
catalytic concrete produced by the Italcementi group (Fig. 13.7b). This
building is often used as reference for the introduction and development
of the use of photocatalytic concrete in Europe. It was fi nished in 2003, and
for 7 years a constant monitoring of its colour was performed on the three
'sails' that form its architecture, showing no change in brightness in the
areas analysed and only slight changes in the colour coordinates a* and b*
on the panels facing south, which was ascribed to the deposition of African
sand carried by the sirocco wind.
A demonstration project was carried out in Bergamo, Italy, where pho-
tocatalytic slabs were installed on a road and related pavement. Two periods
of constant monitoring of NO
x
in the surrounding air, lasting 10 days each,
showed that in the presence of photocatalytic paving slabs, the pollutant
concentration decreased by almost 45%, being the average concentration
in that area in the order of ppbv (Guerrini and Peccati, 2007). Other works
on photocatalytic roads were performed in laboratory and fi eld conditions
by Ballari
et al.
(2010) and in large-scale application by Beeldens (2006) in
Antwerp, Belgium, where a road was paved with photocatalytic building
blocks, revealing again a decrease in NO
x
concentration.
Several other projects have been realized and are still monitored, such
as tunnels, airports and schools, whose exterior walls were either built with
photocatalytic materials or coated with TiO
2
-containing products, such as
mortars, plasters, or just paints.
13.7
Existing patents and standards relating to
photocatalytic cementitious materials
Although the attention of a large part of the scientifi c community has been
devoted to titanium dioxide for decades, practical applications are more
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