1. Friction Surface Treatment Selection: Aggregate Properties, Surface Characteristics, Alternative Treatments, and Safety Effects
S. Li
Indiana Department of Transportation, and 2Purdue University

2. 1. objectives
To evaluate the long-term performance of the selected friction treatments
HFST with calcined bauxite and steel slag, and
Preservation treatments such as chip seal, micro-surfacing, UBWC, and diamond grinding
To determine the crash-friction correlation to establish crash modification factors (CMFs)
To provide original data on HFST aggregates that can be readily implemented by State DOTs
Standard specifications, and
Evaluation of alternative aggregates

3. Micro-Deval Abrasion Loss, % Apparent Specific Gravity
2. Aggregate Properties
Laboratory tests
Mechanical properties: Los Angeles abrasion (LAA), Micro-Deval abrasion, & polished stone value (PSV).
Chemical/physical properties: Al2O3 content, fine aggregate angularity (FAA), and others
Recommendations for aggregate properties
Property
Test Method
Aggregate Size
Calcined Bauxite
Steel Slag
LAA Loss, %
ASTM C131
Grading D
12.5 max
14.0 max
Micro-Deval Abrasion Loss, %
ASTM D6928
6.39.5 mm
5.5 max
6.5 max
PV-10
ASTM D3319
35.0 min
26.0 min
13 mm
55.0 min
49.0 min
Al2O3, % by Mass, %
ASTM C 311
N.A.
86.5 min
5.0 min
Apparent Specific Gravity
ASTM C 127
3.30 min
3.50 min
Water Absorption
ASTM C 127
3.0 max
2.0 max
FAA
AASHTO 304 48 46

4. 3. surface friction Characteristics
Evaluation methods
Laboratory accelerating polishing, and
Actual traffic polishing on test strips
Major factors
Cost: single or double layer application
Appearance/tire wear: aggregate size and gradation
Recommended surface friction characteristics
Property
Test Method
No. 6
Calcined Bauxite
No. 8
Steel Slag
DFT Friction km/h, 90 days
ASTM E 1911
0.90 min
0.65 min
MPD (mm), 90 days
ASTM E 2157
or E 965
1.45 max
1.35 min

5. 4. Pavement preservation Treatments
Evaluation methods
Long-term field friction testing on chip seal, micro-surfacing, UBWC, and diamond grinding
Evaluation results
Chip seal can provide satisfactory friction for five years or more.
Microsurfacing can provide durable friction for six years or more.
UBWC can maintain durable and sound friction under high traffic conditions.
Diamond grinding can provide durable friction for both concrete and asphalt pavements.

6. 5. Crash-friction models
Major distinguishing features
Based on well documented historical crash records and friction test results
Ability to allow for a dynamic evaluation of the CMF due to friction surfacing for life-cycle cost analysis (LCCA).
Prediction models
Road Category
Linear Regression
Fitted Regression
𝐿𝑛 𝛽 0
𝛽 1
R Square
Interstate
0.5779
0.8057
𝑦 𝑖 =1.782 𝑒 −0.046 𝑥 𝑖
State Road
0.4378
0.7669
𝑦 𝑖 =1.550 𝑒 −0.081 𝑥 𝑖
US Route
1.3781
0.9133
𝑦 𝑖 =3.967 𝑒 −0.151 𝑥 𝑖

7. 6. benefits
Provide more realistic estimates on HFST crash reduction. High friction surface treatments are capable of providing crash modification factors of for state roads, for U.S. highways, and for Interstate highways
Provide quantitative friction performance on pavement preservation treatments, including chip seal, microsurfacing, UBWC, and diamond grinding that can be used to address friction concerns at locations with less extreme friction demands.
Provide first-hand data on the mechanistic properties of aggregates for HFST that can be readily implemented by State DOTs.
Provide realistic models that makes it possible to perform life cycle cost analysis (LCCA) for surface treatments