S10_Durability and Performance of Titanium Dioxide in Photocatalytic Pavements_LTC2013 (1)

7/29/2019 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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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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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!

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S10_Durability and Performance of Titanium Dioxide in Photocatalytic Pavements_LTC2013 (1)

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