DURABILITY AND PERFORMANCE OF TITANIUM DIOXIDE IN PHOTOCATALYTIC PAVEMENTS Marwa Hassan Performance Contractors Distinguished Assistant Professor Department of Construction Management 3128 Patrick Taylor Hall Louisiana State University Baton Rouge, LA 70803 Tel: (225) 578-9189
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DURABILITY AND PERFORMANCE
OF TITANIUM DIOXIDE IN
PHOTOCATALYTIC
PAVEMENTS Marwa Hassan Performance Contractors Distinguished Assistant Professor
Department of Construction Management
3128 Patrick Taylor Hall
Louisiana State University
Baton Rouge, LA 70803
Tel: (225) 578-9189
Introduction
The US faces a significant challenge in controlling
air pollution from transportation activities
Road microenvironments contribute:
29% of the volatile organic compounds
35% of the nitrogen oxides (NOx)
58% of the carbon monoxide
Tall buildings prevent the dispersion of air
pollutants in urban areas
Introduction
35 million Americans live within 300ft from roads
Decomposition of pollutants by ultraviolet (UV)
radiation is extremely slow
2008 Non-Attainment Areas (EPA)
Photocatalytic Uses of TiO2
Architectural Facades
Statues
Highway Sound Barriers
Tiles
PAVEMENTS
Photocatalytic Mechanism
Titanium dioxide forms highly oxidizing holes and
photo-generated electrons resulting in powerful
oxidizing and reductive agents hydroxyl radicals and
superoxides.
Conduction
Band
Valence Band
Light (hv) Eg =3.2 eV
H2O
TiO2
e-
h+ Hydroxyl radical
(·OH)
Superoxides
(O2-)
Photocatalytic Mechanism
Surface
NOx, SO2, VOC
TiO2 TiO2 NO3-
NO3-
UV radiation
Rain
NOx Photodegradation
NOx Degradation:
Sulfur dioxide is decomposed to sulfate
Hydrophobic or hydrophilic properties of the
surface allow them to self-clean in the presence of
rain
Photodegradation Efficiency
TiO2 crystal (anatase, brookite, rutile)
Substrate
Application method
Concentration of TiO2
Type and Concentration of Pollutants
Flow Rate
Relative Humidity
Interaction between multiple pollutants
UV light intensity
Photocatalytic degeneration and regeneration.
Titania Research at LSU
Laboratory evaluation of concrete pavement treated with TiO2:
Methods of applications
Impacts of environmental conditions (relative humidity, pollutants flow rate, solar radiation)