Summary of CTDOT Thin Friction Wearing Course
Scott Zinke
Summary of CTDOT Thin Friction Wearing Course
Connecticut Advanced Pavement Lab UConn
Why Thin Friction Wearing Course (TFWC)? • Add to portfolio of Pavement Preservation options for CTDOT • Develop high friction surface course that can be placed with standard paving equipment
• Enhance safety through increased tire-road surface friction
Focus of TFWC Development • Open surface texture to maximize tire-pavement friction with minimal permeability through the layer • Limit to maximum 3/8” stone to accommodate thin placement • Modified asphalt binder to enhance asphalt binder film thickness to enhance elasticity, adhesion and durability with the limited fine aggregate in the mix
TFWC Development as Pavement Preservation Treatment • Quality surface conditions • No structural defects
• Seal cracks
Mixture Gradation • Emphasis is on the reduction of fine aggregate
• Similar sized densegraded mixes may commonly have as much as 70% passing the #4 screen
Asphalt Binder Requirements
• PG 76-22 or • PG 64E-22
• Must contain SBS polymer
Mixture Requirements • 50 Gyrations • Air Voids = 5.0 ± 1.0 % • Minimum AC ≥ 6.0 % • VMA ≥ 18.0% • No RAP • No RAS • No Glass
Mixture Performance Requirements AASHTO T 283 Moisture Induced Damage
AASHTO T 305 Draindown
Delivery and Placement Special Requirements • MTV should be required • Tack is required • Final compacted thickness = 1.0 inches ± 0.25 inches
Compaction Requirements
• Minimum of two 10-ton rollers • One roller must operate in vibratory mode • First 3 passes must be in vibratory mode ≥ 12 impacts per foot • Final 2 passes in static mode ≤ 6.0 mph • Completed before pavement temperature < 200.0 ⁰F
Trial Location Rt. 12 Preston/Ledyard, CT August – September 2012
• 1.63 miles of TFWC
• ADT ~11,500
Texture Observation 1 Day Following Placement
Texture Observation 5 years 7 Months Following Placement
General Condition 1 Day Following Placement
General Condition 5 Years 7 Months Following Placement
Current General Condition Notes • Asphalt has worn off the surface aggregate as expected • No cracking • No other obvious forms of distress
21 Month Smooth Tire Friction Performance Comparison 21 Month Smooth Tire Friction Performance 65
60
Smooth Tire Friction #
55
50 TFWC 45
Dense
40
35
30 0
2
4
6
8
10
12
Months Since Placement
14
16
18
20
22
21 Month Ribbed Tire Friction Performance Comparison 21 Month Ribbed Tire Friction Performance 65
60
Ribbed Tire Friction #
55
50 TFWC 45
Dense
40
35
30 0
2
4
6
8
10
12
Months Since Placement
14
16
18
20
22
Skid Performance (Smooth Tire) 5 Year Smooth Tire Friction Performance TFWC 65
60
Smooth Tire Friction #
55
50
45
40
35
30 0
10
20
30
40
Months Since Placement
50
60
70
Skid Performance (Ribbed Tire) 5 Year Ribbed Tire Friction Performance TFWC 65
60
Ribbed Tire Friction #
55
50
45
40
35
30 0
10
20
30
40
Months Since Placement
50
60
70
Conclusions To Date: • Contractor found TFWC easier to produce and place as compared to Ultra-Thin Bonded Wearing surface • The mix is not cracking or otherwise degrading • Friction performance has remained steady and satisfactory
Thank You!
Scott Zinke Connecticut Advanced Pavement Lab Connecticut Transportation Institute
UCONN
Summary of CTDOT Thin Friction Wearing Course
Connecticut Advanced Pavement Lab UConn
Why Thin Friction Wearing Course (TFWC)? • Add to portfolio of Pavement Preservation options for CTDOT • Develop high friction surface course that can be placed with standard paving equipment
• Enhance safety through increased tire-road surface friction
Focus of TFWC Development • Open surface texture to maximize tire-pavement friction with minimal permeability through the layer • Limit to maximum 3/8” stone to accommodate thin placement • Modified asphalt binder to enhance asphalt binder film thickness to enhance elasticity, adhesion and durability with the limited fine aggregate in the mix
TFWC Development as Pavement Preservation Treatment • Quality surface conditions • No structural defects
• Seal cracks
Mixture Gradation • Emphasis is on the reduction of fine aggregate
• Similar sized densegraded mixes may commonly have as much as 70% passing the #4 screen
Asphalt Binder Requirements
• PG 76-22 or • PG 64E-22
• Must contain SBS polymer
Mixture Requirements • 50 Gyrations • Air Voids = 5.0 ± 1.0 % • Minimum AC ≥ 6.0 % • VMA ≥ 18.0% • No RAP • No RAS • No Glass
Mixture Performance Requirements AASHTO T 283 Moisture Induced Damage
AASHTO T 305 Draindown
Delivery and Placement Special Requirements • MTV should be required • Tack is required • Final compacted thickness = 1.0 inches ± 0.25 inches
Compaction Requirements
• Minimum of two 10-ton rollers • One roller must operate in vibratory mode • First 3 passes must be in vibratory mode ≥ 12 impacts per foot • Final 2 passes in static mode ≤ 6.0 mph • Completed before pavement temperature < 200.0 ⁰F
Trial Location Rt. 12 Preston/Ledyard, CT August – September 2012
• 1.63 miles of TFWC
• ADT ~11,500
Texture Observation 1 Day Following Placement
Texture Observation 5 years 7 Months Following Placement
General Condition 1 Day Following Placement
General Condition 5 Years 7 Months Following Placement
Current General Condition Notes • Asphalt has worn off the surface aggregate as expected • No cracking • No other obvious forms of distress
21 Month Smooth Tire Friction Performance Comparison 21 Month Smooth Tire Friction Performance 65
60
Smooth Tire Friction #
55
50 TFWC 45
Dense
40
35
30 0
2
4
6
8
10
12
Months Since Placement
14
16
18
20
22
21 Month Ribbed Tire Friction Performance Comparison 21 Month Ribbed Tire Friction Performance 65
60
Ribbed Tire Friction #
55
50 TFWC 45
Dense
40
35
30 0
2
4
6
8
10
12
Months Since Placement
14
16
18
20
22
Skid Performance (Smooth Tire) 5 Year Smooth Tire Friction Performance TFWC 65
60
Smooth Tire Friction #
55
50
45
40
35
30 0
10
20
30
40
Months Since Placement
50
60
70
Skid Performance (Ribbed Tire) 5 Year Ribbed Tire Friction Performance TFWC 65
60
Ribbed Tire Friction #
55
50
45
40
35
30 0
10
20
30
40
Months Since Placement
50
60
70
Conclusions To Date: • Contractor found TFWC easier to produce and place as compared to Ultra-Thin Bonded Wearing surface • The mix is not cracking or otherwise degrading • Friction performance has remained steady and satisfactory
Thank You!
Scott Zinke Connecticut Advanced Pavement Lab Connecticut Transportation Institute
UCONN
