Feasibility Investigation of Superhydrophobic Engineered Asphalt

Concrete for Roadway Winter Maintenance

Ali Arabzadeh1, Therin Young2

Halil Ceylan1, Sriram Sundrarajan2

Sunghwan Kim1 and Kasthurirangan Gopalakrishnan1

1Dept. of Civil, Construction and Environmental Engineering (CCEE)2Dept. of Mechanical Engineering (ME)

Program for Sustainable Pavement Engineering and Research (PROSPER)Institute for Transportation (InTrans), Iowa State University (ISU)

2015 Mid-Continent Transportation Research Symposium Gateway Hotel and Conference Center, Ames, IA, August 19–20, 2015

ACKNOWLEDGEMENTS

• Iowa State University • FAA and PEGASAS

2

OUTLINE

• Background• Methodology• Results• Conclusions

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BACKGROUND

• Each year billions of dollars are spent for: Snow and ice removals Weather damage to roadways Revenue lost to closed businesses

• 76,300 flight cancellations in 2014 Leaving millions of travelers in lurch Costing airlines and airports millions

4

• Problems Associated with Ice Formation and Snow Accumulation on Roadways and Runways

BACKGROUND

5

www.beaumontenterprise.com

www.vosizneias.com Courtesy: CNN

www.warbird-central.com

• Ice and Snow Removal on other Outdoor Structures

BACKGROUND

6

Wind turbines Telecommunication antennasJet engines

Airplane wings Power lines lines

www.aeml.tech.purdue.edu www.ibtimes.co.uk

www.ucar.edu www.reddit.comwww.safesetbacks.com

• Hydrophobicity Concept Models explaining

the hydrophobicity

BACKGROUND

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Lotus leaf

Young Wenzel Cassie-Baxter

www.flickr.com

www.roadandtrack.com

(Gao et al., 2009)

• Contact Angle Hydrophobic

Superhydrophobic

Hydrophilic

𝜭𝜭≥150

BACKGROUND

8

𝜭𝜭 ˃ 90 𝜭𝜭 ˂ 90

• Main Concern in Nano-Coated Roadways/Runways High skid resistance

in dry condition• Components Affecting the Pavement

Friction Pavement surface-tire interaction Aggregate micro-asperities

BACKGROUND

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BACKGROUND

• Types of Asperities Micro-texture (0.005-0.3 mm) Macro-texture (0.3-4.0 mm) Mega-texture (˃ 4.0 mm)

• Micro-Texture Contribution to Skid Resistance Low speeds High speeds

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OUTLINE

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• Background• Methodology• Results• Conclusions

• Sample Preparation A statistical design

was developed Cylindrical asphalt

concrete specimens were prepared and cut to obtain disk-shaped substrates

Each substrate was divided into four quarters

METHODOLOGY

Aggregate Specific gravity (g/cm3)

Absorption (%)

Limestone 2.76 1.44Asphalt binder

Specific gravity (g/cm3)

Penetration value (0.1mm)

PG58-28 1.028 75

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0102030405060708090

100

0 0.5 1 1.5 2 2.5 3 3.5 4

Pass

ing

(%)

Sieve size ^ 0.45 (mm)

Restricted zone

Maximum densitylineControl points

Blend

METHODOLOGY

• Coating 1LBL method

was selected First epoxy

and xylene was sprayed

Then, 2PTFE mixed with acetone was applied

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Material Control Knob

Fan Control Knob

Asphalt Concrete Specimen

PTFE Nanoparticles

Epoxy Resin

Asphalt Concrete Substrate

Air Inlet

Paint Cup Pressur

e Gage

Atmospheric Air Compressor

15 cm

(Low amount of PTFE)

Note: 1LBL stands for layer by layer, and2PTFE stands for polytetrafluoroethylene

(High amount of PTFE)

METHODOLOGY

• Water Droplet Magnification

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4 µL Water DropletSony Camera

Spacer Block

Coated Asphalt Concrete Specimen

Probe

SpacerBlock

Sample Stage (Lateral Force)

Strain Gages (Normal) (Lateral)

Vertical Stage

Micrometer

Two-Sided Tape

Probe Arm

Asphalt Concrete Specimen

Friction Measurement

Paths

(Side View)

(Top View)

• Data Collection for Measuring the Coefficient of Friction Vertical Load

(20-40 mN) Constant speed

(5 mm/s) Constant distance

(10 mm)

METHODOLOGY

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OUTLINE

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• Background• Methodology• Results• Conclusions

• Nano-Coated Asphalt Concrete Hydrophobic Icephobic

RESULTS

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Coated Uncoated

• Water contact angle measurement Sessile-drop and tangent line method

RESULTS

SprayTime

(s)

PTFE (%)10 20 30 40

Ave.1 SE2 Ave. SE Ave. SE Ave. SE3 125 8.3 152 5.4 155 2.6 150 4.86 156 2.9 157 3.1 156 2.5 155 1.79 161 3.2 154 5.8 165 2.5 158 2.1

12 156 9.0 156 3.9 161 1.6 166 1.5

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α = 154° α = 161° α = 160°

Note: 1Ave stands for the average and 2SE stands for the standard error

2-way ANOVASources PPTFE (%) 0.016

Spray time 0.0002˂ 0.05˂ 0.05

Confidence interval of 95%

RESULTS

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• Measurement of Coefficient of Friction

y = 0.2532x - 4.0642R² = 0.9955

0

1

2

3

4

5

6

7

8

9

15 20 25 30 35 40 45 50

Fric

tion

forc

e (m

N)

Normal force (mN)

0.19 0.

20

0.16

0.16

0.19

0.26

0.19

0.23

0.15

0.23

0.23

0.27

0.17

0.26

0.24

0.24

0.21

0.21

0.21

0.21

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.35

3 6 9 12

Coe

ffici

ent o

f fric

tion

Spray time (seconds)

10% 20% 30% 40% Control

2-way ANOVASources PPTFE (%) 0.001

Spray time 0.0001

Confidence interval of 95%

˂ 0.05˂ 0.05

µ𝑘𝑘= 0.25

OUTLINE

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• Background• Methodology• Results• Conclusions

CONCLUSIONS

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• LBL method for PTFE deposition seems to be a promising method

• Micro-tribometer is an appropriate device for measuring the coefficient of friction

• Spray time significantly affects the superhydrophobicity and skid resistance of the coated asphalt concrete samples

CONCLUSIONS

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• In the context of micro-texture, PTFE results in obtaining comparable or higher skid resistance in the nano-coated asphalt concrete at a certain spray time

• In the context of macro-texture, shape, distribution and angularity of the coarse aggregate are the main contributors to improving the skid resistance

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Thank You!Questions & Comments?