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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
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
7
Lotus leaf
Young Wenzel Cassie-Baxter
www.flickr.com
www.roadandtrack.com
(Gao et al., 2009)
• 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
9
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
10
• 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
12
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
13
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
14
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
15
• 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
18
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
19
• 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
CONCLUSIONS
21
• 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
22
• 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