Civil Engineering Reference
In-Depth Information
New material
Aged material
Carbonation
products
Pollutants
Porosity
UV light
UV light
Pollutants
TiO
2
TiO
2
Cement paste
Cement paste
13.8
Scheme of possible progressive shielding of photocatalyst due to
material ageing.
tantly if the whole structure is built with photocatalytic concrete, since its
degradation cannot be easily overcome by substitution or re-application. A
guideline dedicated to solving design issues with photocatalytic materials
would therefore be a desirable target of further research.
13.5 Effi ciency of TiO
2
in the built environment
Experimental works concerning the use of TiO
2
nanopowders in the con-
struction fi eld are variegated in terms of substrate material (bare cement
pastes, mortars, concrete), composition (mix proportions with different
binder, water/binder ratio, photocatalyst concentration, type and quantity
of sand/aggregates, additives) and fi nal application (precast panels, paving
blocks, concrete pavements, cement-based tiles, indoor and outdoor walls,
masonry blocks).
Characterization tests performed are also numerous, all involving a more
or less intense and prolonged irradiation with UV light or simulated sun-
light. Different experimental setups are applied in laboratory testing,
depending on the property to be tested:
• photocatalytic activity: measurement of the extent of gas phase degrada-
tion of inorganic pollutants (NO
x
) or volatile organic compounds
(VOCs) at the material surface
• self-cleaning: introduction of the material in a closed chamber with
soiling atmosphere, or impregnation with an organic dye, and monitor-
ing of colour loss (colour recovery); analysis of chromatic changes
during extended exposure of materials to the external environment
• superhydrophilicity: measurement of contact angle of water on the
material surface
•
antibacterial and anti-vegetative effect: inhibition of biofi lm formation,
algae adhesion and proliferation, and sterilization effects.
Search WWH ::
Custom Search