s10_durability and performance of titanium dioxide in photocatalytic pavements_ltc2013 (1)
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DURABILITY AND PERFORMANCE
OF TITANIUM DIOXIDE INPHOTOCATALYTIC
PAVEMENTSMarwa HassanPerformance Contractors Distinguished Assistant Professor
Department of Construction Management
3128 Patrick Taylor Hall
Louisiana State University
Baton Rouge, LA 70803Tel: (225) 578-9189
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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 airpollutants in urban areas
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Introduction
35 million Americans live within 300ft from roads
Decomposition of pollutants by ultraviolet (UV)
radiation is extremely slow
2008 Non-Attainment Areas (EPA)
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Photocatalytic Uses of TiO2
Architectural Facades
Statues
Highway Sound Barriers
Tiles PAVEMENTS
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Photocatalytic Mechanism
Titanium dioxide forms highly oxidizing holes and
photo-generated electrons resulting in powerful
oxidizing and reductive agents hydroxyl radicals and
superoxides.
ConductionBand
ValenceBand
Light(hv) Eg =3.2 eV
H2O
TiO2
e-
h+ Hydroxyl radical(OH)
Superoxides
(O2-)
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Photocatalytic Mechanism
Surface
NOx, SO2,
VOC
TiO2 TiO2 NO3- NO3-UV
radiation Rain
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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
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Photodegradation Efficiency
TiO2 crystal (anatase, brookite, rutile)
Substrate
Application method
Concentration of TiO2Type and Concentration of Pollutants
Flow Rate
Relative Humidity
Interaction between multiple pollutantsUV light intensity
Photocatalytic degeneration and regeneration.
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Titania Research at LSU
Laboratory evaluation of concretepavement treated with TiO2:
Methods of applications
Impacts of environmental conditions (relative humidity,pollutants flow rate, solar radiation)
Effectiveness on NOx and SO2 degradation
Design variables (aggregate gradation, TiO2
concentration)
Durability of Photocatalytic layer
Photocatalytic Pervious Concrete Pavement
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Titania Research at LSU
Laboratory evaluation of asphaltpavement treated with TiO2:
Methods of applications
Impacts of environmental conditions (relative humidity,pollutants flow rate, solar radiation)
Durability & Effects on mix performance (fractureresistance, thermal cracking, and rutting performance)
Photocatalytic Warm-Mix Asphalt
Effect of TiO2 on HMA and WMA aging
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Titania Research at LSU
Field evaluation of asphalt and concretepavement treated with TiO2:
Hassan and co-workers laid the countrys first air-
purifying asphalt and concrete photocatalytic pavementson Dec. 20, 2010
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Phase I: Laboratory Evaluation
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Sample Preparation
Application of Water-Based
TiO2 Solution
Curing and sprinkling nano-sized
TiO2 particles 10mm thin
surface mixturewith TiO2
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Application Method HMA & WMA
Spray-Coating Application of TiO2:
A thin nano film is spray-coated on each sample
a mixture of TiO2 anatase nanoparticles with an average
size of 6nm suspended in an aqueous liquid at 2% byvolume.
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Laboratory Setup
Illustration of the
Environmental Setup
Photoreactor
NOx
Analyzer
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Photocatalytic Efficiency
NO Reduction Efficiency
-100
0
100
200
300
400
500
0 :0 0 0 :3 0 1 :0 0 1 :3 0 2 :00 2 :30 3: 00 3 :3 0 4 :0 0 4 :3 0 5 :0 0 5 :3 0 6 :00 6 :3 0 7: 00 7 :3 0 8 :0 0
Concentration(ppb)
duration (h:mm)
NOx NO2 NO
Average Reduction Trial 2 - 242 ppb
% Reduction Trial 2 - 56.4%
Light On Light Off
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Results and Analysis
Water vapor can have both negative and positiveimpacts on the environmental performance ofTiO2
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Results and Analysis
The longer the residence time the moreNO reduced.
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Experimental Setup
Hamburg Type Loaded Wheel
Tester
Concrete Asphalt
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Durability Results and Analysis
WMA &HMA
NOx Removal Efficiency decreased afterloading in the LWT.
0
10
20
30
40
50
60
SC-64L1 SC-64L2 SC-64L3 SC-70L1 SC-70L2 SC-70L3
NOxReduction
Efficiency
Sample ID
Before LWT
After LWT
0.0
5.0
10.0
15.0
20.0
25.0
H64CO H64-7 H70CO H70-7 W64CO W64-7 W70CO W70-7
RutDepth(mm)
Mixture ID
HMA WMA
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Durability Results and Analysis -
Concrete
Durability: Loaded-Wheel Tester The measured rut depth for all specimens
was minimal (less than 1mm).
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Experimental Testing
Abrasion testing: according to ASTM C 944
Test method uses a cutter rotating at 200 rpm under a
constant load of 98 N for 2 minutes to wear the
coating surface.
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Durability Results and Analysis -
concrete
A thin coating would be more susceptible toabrasion than the photocatalytic compoundapplied using the sprinkling method or usingthe PT product.
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Effect of Weathering
LWT slightly improved the NO removalefficiency of the different samples
The weathering action exposed part of the embeddedtitanium dioxide particles at the surface
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Pervious Concrete
Samples are prepared in two layers:
Bottom lift: standard pervious concrete
Upper lift: prepared with photocatalytic specialty cement
Depth of the photocatalytic layer was varied between fourlevels: 0.5, 1, 2, and 3 in.
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Effect of TiO2 depth
The increase in depth resulted in an increase in NOxremoval efficiency
9%
30%
35%
39%
50%
9%
34%40%
45%
53%
0%
10%
20%
30%
40%
50%
60%
70%
Control 0.5 1 2 3
Rem
ovalEfficiency
Depth (inch)
NOx NO
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Phase II: Field Installation and Evaluation
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Field Installation
First field installation of TiO2 on pavement in the US(12/2010)
The test area is a pavement site located on LSU
campus Many states (e.g., Virginia, Texas, Vermont, New
York, and Missouri) will or are evaluating thetechnology
The spray coating used was a mixture of TiO2anatase nanoparticles with an average size of 6nmsuspended in an aqueous liquid at 2% by volume
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Field Installation
A customized distributor truck was used in theapplication of TiO2 water-based solution
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Field Monitoring : Direct Method
NO concentration is measured at the pavement
level by placing a perforated pipe at the surface in
the middle of the lane
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Field Effectiveness
Indirect Method: Nitrate Analysis
Field measurements were conducted to quantify theamount nitrate deposited on the pavement surface
+
2 + .
2 +
2
3+
.
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Field Effectiveness
There is definite evidence that photocatalytic
degradation of nitrogen oxide is taking place
in the field in the treated section
0
0.1
0.2
0.3
0.4
0.5
1 2 3 4 5 6 7
AverageNitrate(mg/l)
Day
Treated Section Untreated Section
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Cost Analysis
Cost Increase is 4.4%
Costs will decrease significantly once TiO2 ismass produced in the US reducing in bothmaterial and delivery costs.
Cost Estimate Cost ($/yd2)2009 RS Means 10 inch concrete paving surface 42.93
Photocatalytic Coating 1.88
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Conclusions
Applying TiO2 as close as possible tothe source of pollution can remove asignificant portion of NOx pollutants
from the atmosphere when placed. Field measurements show that
photocatalytic degradation of
nitrogen oxide is taking place in thefield in the treated section.
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Conclusions
The NO removal efficiency decreasedwith the increase in humidity levelWater inhibits absorption of NO by the photocatalytic
compoundAs the flow rate increased, the percent
NO removal efficiency decreased
As the residence time decreased, it allows less time forthe pollutants to be absorbed by the photocatalyticcompound
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Additional work is needed..
Evaluate influence of other pollutants (VOCs) and
mixed air pollutants.
Full-scale controlled evaluation in accelerated
facility is needed
Long-term environmental performance and
durability
Assess the potential impacts of photocatalytic TiO2pavement surface coating on the aquatic
environment
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Acknowledgments
This research was sponsored through LTRC, NSF, and
the Gulf Coast Research Center for Evacuation and
Transportation Resiliency
The assistance of the concrete and asphalt
laboratory staff at LTRC is greatly appreciated
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Thank You!