MS DOT Friction Study
and
DFT Workshop
Dr. Michael Heitzman, PE
Assistant Director
National Center for Asphalt Technology
NCAUPG – Kansas City – February 19-20, 2014
1
MS DOT Study Objective
To use the laboratory TWPD conditioning and
DFT/CTM testing protocol developed at NCAT to
better understand the influence of friction
aggregate in a typical gravel-limestone 9.5 mm
surface mixture and in an ultra-thin surface
mixture (4.75 mm)
2
Work Plan
1. Identify 9.5 mm and ultra-thin mixtures for the study
2. Determine the friction aggregate substitutions
• Slag
• Granite
• Crushed gravel
3. Prepare three replicate test slabs
4. Test two replicate slabs
5. Analyze the data
6. Report
3
9.5 mm Mixture
and Aggregate Substitutions
1. Identify 9.5 mm mixture
• 65% crushed gravel (50% +No.8)
• 24% limestone (8% +No.8)
• 10% sand
2. Determine the coarse aggregate substitutions (+No.8)
• 33% & 60% slag
• 33 % & 60% granite
3. Screen the source gradations for blending (split on No.8)
4. Prepare three replicate test slabs of each mix with PG 67 -22
binder compacted to 7% air voids
4
9.5 mm Mixture with Slag
5
9.5 mm Mixture with Granite
6
% of Mix (by total aggregate volume)
Mix Designation
1.0
1.1
1.2
1.3
1.4
Control
33% Slag
60% Slag
33% Granite
60% Granite
Cr GVL +#8s
51.6
25.8
Cr GVL -#8s
15.1
15.1
15.1
13.7
12.6
LMS 820 +8s
7.6
7.6
7.6
6.9
6.4
LMS 820 -8s
14.7
14.7
14.7
13.4
12.3
Coarse Sand +8s
0.5
0.5
0.5
0.5
0.4
Coarse Sand -8s
9.4
9.4
9.4
8.5
7.8
Hyd. Lime
1.1
1.1
1.1
1.0
0.9
25.8
51.6
32.5
59.6
Material
Slag +#8s
23.5
GRN +#8s
7
Ultra-thin Mixture
and Aggregate Substitution
1. Identify ultra-thin mixture
• 70% limestone
• 10% natural sand
• 19% manufactured sand
2. Determine the total aggregate substitutions
• 25% & 50% crushed gravel
3. Screen the source gradations for blending (split on No.16)
4. Prepare three replicate test slabs with PG67 -22 binder
compacted to 7% air voids
8
% of Mix (by total weight of aggregate)
Mix Designation
2.0
2.1
25% Cr. Gravel
2.2
Material
Control
810 LMS
56.0
45.0
20.0
89 LMS
14.0
0.0
0.0
Coarse Sand
10.0
10.0
10.0
Manuf. Sand
19.0
19.0
19.0
Hydrated Lime
1.0
1.0
1.0
25.0
50.0
-1/2 Cr. Gravel
9
50% Cr. Gravel
Ultra-thin Mixture with Cr. Gravel
10
Preparing Mix Slabs
11
Test Protocol
Test two replicate slabs (grouped by TWPD unit)
0-0.5-1-2-5-10-20-40-60-100K cumulative polishing cycles
12
Dynamic Friction Tester (DFT)
• Tests conducted at specific
intervals during polishing
(0,0.5, 1, 2, 5, 10….100k cycles).
• Three replicate measurements.
• Friction values are measured at
0, 20, 40, 60 and 80 km/h.
• Test Procedure ASTM E 1911
13
DFT Output
14
Circular Texture Meter (CTM)
• Tests conducted at specific
intervals during polishing
(0,0.5, 1, 2, 5, 10….100k cycles).
• Five replicate measurements.
• Mean Profile Depth (MPD)
and Root Mean Square (RMS).
• Test Procedure ASTM E2157.
15
CTM Output
16
NCAT Three Wheel Polishing Device
Motor
Load
Counter
Pneumatic Tires
Water Tank
HMA Slab
17
17
Mix Data Analysis – DFT Data QC
9.5 mm
Ultra-thin
18
9.5 mm Mixture Results - DFT
19
Ultra-thin Mixture Results - DFT
20
9.5 mm Mixture Results - CTM
21
Ultra-thin Mixture Results
22
Conclusions
 Slag improved the 9.5 mm mix friction more than
the granite
 Crushed gravel improved the ultra-thin mix
friction
23
Dynamic Friction Tester
Workshop
July 22-23, 2013
sponsored by FHWA
24
Workshop Participants
 FHWA
 Penn State
 NCAT
 U of Kentucky
 Maryland SHA
 Transtec Group
 Texas DOT / Texas A&M
 Shima America
 Indiana DOT / NCSC
 Nippo Sangyo
 Virginia DOT / Virginia Tech  American Civil Constructors
 Florida DOT
DFT Workshop July 2013
25
Workshop Agenda
 Features and Calibration
 Results of Round-Robin Testing
 Pavement Slope and Rutting
 Single Test Replicate Drops
 Use of Rubber Slider Pads
 Correlation with Skid Trailer
 Improvements to ASTM E1911
DFT Workshop July 2013
26
Round-Robin Test Results
 Factors
 10 pavement sections
 10 devices
 5 replicate drops
 25 total drops
 3 measurement speeds
DFT Workshop July 2013
27
General Linear Model: DFT versus Device, Speed, Section
Factor
Device
Speed
Section
Type
fixed
fixed
fixed
Levels
10
3
10
Values
1, 2, 3, 4, 5, 6, 7, 8, 9, 10
20, 40, 60
1, 2, 3, 4, 5, 6, 7, 8, 9, 10
Analysis of Variance for DFT, using Adjusted SS for Tests
Source
Device
Speed
Section
Device*Speed
Device*Section
Speed*Section
Device*Speed*Section
Error
Total
S = 0.0104923
DF
9
2
9
18
81
18
162
1200
1499
Seq SS
3.715244
0.013457
2.823384
0.034455
0.572555
0.106572
0.044464
0.132105
7.442236
R-Sq = 98.22%
Adj SS
3.715244
0.013457
2.823384
0.034455
0.572555
0.106572
0.044464
0.132105
Adj MS
0.412805
0.006729
0.313709
0.001914
0.007069
0.005921
0.000274
0.000110
R-Sq(adj) = 97.78%
28
F
3749.80
61.12
2849.64
17.39
64.21
53.78
2.49
P
0.000
0.000
0.000
0.000
0.000
0.000
0.000
General Linear Model: DFT versus Device, Speed, Section
Grouping Information Using Tukey Method and 95.0%
Confidence
Device
1
6
10
5
9
4
7
3
2
8
N
150
150
150
150
150
150
150
150
150
150
Mean
0.4126
0.4083
0.3996
0.3898
0.3749
0.3651
0.3538
0.3464
0.3400
0.2320
Grouping
A
B
C
D
E
F
G
H
I
J
Means that do not share a letter are significantly
different.
29
General Linear Model: DFT versus Device, Speed, Section
Drop Device #8
Factor
Device
Speed
Section
Type
fixed
fixed
fixed
Levels
9
3
10
Values
1, 2, 3, 4, 5, 6, 7, 9, 10
20, 40, 60
1, 2, 3, 4, 5, 6, 7, 8, 9, 10
Analysis of Variance for DFT, using Adjusted SS for Tests
Source
Device
Speed
Section
Device*Speed
Device*Section
Speed*Section
Device*Speed*Section
Error
Total
DF
8
2
9
16
72
18
144
1080
1349
Seq SS
0.887213
0.016058
2.712635
0.030906
0.521717
0.107742
0.036949
0.124785
4.438005
Adj SS
0.887213
0.016058
2.712635
0.030906
0.521717
0.107742
0.036949
0.124785
S = 0.0107490
R-Sq = 97.19%
30
Adj MS
0.110902
0.008029
0.301404
0.001932
0.007246
0.005986
0.000257
0.000116
F
959.84
69.49
2608.62
16.72
62.71
51.81
2.22
P
0.000
0.000
0.000
0.000
0.000
0.000
0.000
R-Sq(adj) = 96.49%
Correlation with Skid Trailer
 Compare SN40R to DFT(20)
 Compare SN40R to DFT(40)
 Compare SN40R to DFT(60)
Round Robin Results
DFT Workshop July 2013
31
ASTM E1911-09a
 Sec 6.3 – 12 drops
 Sec 6.6 – DFT(40) within 0.03
 Sec 7.1/8.1 – horizontal, flat surface
 Sec 9.1.2 – report 80 km/h
 Sec 10.1 – based on 8 replicates
 Annex (‘02) - calibration
DFT Workshop July 2013
33
Michael Heitzman, PE PhD
34
[email protected]