Thin Hot Mix Asphalt Overlays

Transcription

1 Plant Certification Program 2017 Thin Hot Mix Asphalt Overlays 1 Outline 1 THMAO As A Pavement Preservation Strategy 2 Mix Design and Evaluation Construction Quality Control Performance Evaluation 2

2 1 THIN OVERLAYS FOR PAVEMENT PRESERVATION 33 Roadway Improvement Activities Activity Reconstruction Major Rehabilitation Minor Rehabilitation Pavement Preservation Preventive Maintenance Routine Maintenance Increase Capacity Increase Structural Strength? Improve Pavement Condition Restore Serviceability Extend Service Life Depends 4

3 How Thick is Thin Asphalt? Placed up to 1.25 inches in thickness Ultrathin layers: between 0.5 and Practice in Other States State Term Type Sieve mm IN MI NC Ultrathin Bonded Wearing Course HMA Ultra- Thin Ultrathin Bonded Wearing Course 4.75mm mm %Pass Thickness, in 3/4-1 3/4 1/2 1 Mostly 5/8

4 Practice in Other States State Term Type Sieve mm NY OH TX 6.3 mm Polymer Modified HMA Smoothseal Crack Attenuating Mix (CAM) Type A Type B %Pass (Max) Thickness, in 3/4-1 5/8 3/4 3/4-1 Mat Thickness/NMAS Ratio NMAS: Nominal Max. Aggregate Size Aggregate NMAS Mat Thickness 0.5 to 1.25 in 3 Ratio of Thickness to NMAS 5 88

5 Importance of NMAS in Thickness Table shown with: Mat Thickness: from 1.5 inches to 0.50 inches, and NMAS: from 12.5 mm to 4.75 mm Good Ok Avoid 99 Mat Thickness In mm NMAS Ratio Significance of Aggregate Skid Resistance Level in Thin Asphalt Two of the Most Important Properties Affecting Friction (Skid Resistance) Are: 1. Aggregate Microtexture 2. Pavement Macrotexture 10

6 Significance of SRL in Thin Asphalt Micro (texture of stone) Macro (texture of road) As thickness gets smaller, harder to develop macro and more demand on micro MIX DESIGN AND EVALUATION 1212

7 6.3 mm NMAS Mix Placed at 1 inch thickness Aggregate: Skid Resistance Level (SRL): E Polymer Modified Binder: PG (for heavier traffic) Gyration Level: 75 Design Air Void: 4%, Min. Design VMA: 16.5% Design Binder Content: 6.7%; 7.0%; 6.9% NO RAP/RAS 13 Performance Evaluation - HWTD Specimens under water Test Temperature: 50ºC 20,000 Passes 50 Passes per minute 158-lb load 14

8 6 5 Performance Evaluation - HWTD Thin Asphalt Overlay Project Hamburg Wheel Tracking Tests - 8/23/ st Pilot Project Rut Depth, mm Right Track Left Track Temperature = 50ºC Number of Wheel Passes (X1000) 15 Performance Evaluation Texas Overlay Tester 16

9 Performance Evaluation Overlay Tester Test Temperature: 25ºC # of load cycles: 1000 Or until load reduced to 93% of original Repeated loading (triangular form) under constant deformation Deformation magnitude per load cycle: inches (0.6 mm) Duration of each load cycle: 10 seconds 17 Cycles to failure > 500 Good Performance Tack Coat Evaluation Direct Shear Applied at the Asphalt-Concrete Interface Horizontal Load Asphalt Counterbalancing Moment Tack Coat Horizontal Load Counterbalancing Moment 18 Concrete

10 Tack Coat Evaluation Trimmed Core Tested Specimen in Direct Shear 19 Tack Coat Evaluation Shear Strength = 44.5 psi (307 KPa) - Good Performance THMAO Project Tack Coat Evaluation - Core # 5 Interface Shear Stress, KPa Deformation Rate: 1 mm/min Test Temperature: 25.5 C Interface Shear Deformation, mm 20

11 Recommended Requirements for Design of Asphalt Mix for Thin Lifts Tack Coat, CSS-1h Surface Type Residual Application Rate (Gallons/Square Yard) New Asphalt Mixture 0.03 to 0.04 Oxidized Asphalt Mixture 0.04 to 0.06 Milled Asphalt Mixture 0.05 to 0.07 Milled PCC 0.05 to 0.07 Portland Cement 2121 Concrete 0.05 to CONSTRUCTION OF THIN OVERLAYS 222

12 Repair/Prepare the Base 2323 Repair/Prepare the Base 2424

13 Repair/Clean before Tacking 25 Emulsion Tack Coat Application 26

14 Rollers Follow Paver Closely Concern with Mat Temperature 2727 Finished Overlay 1 st Project 28

15 Finished Overlay 2 nd Project 29 Finished Overlay- 3 rd Project 30

16 4 QUALITY CONTROL OF THIN OVERLAYS 3131 Thermal Segregation T 25 ºF T 50 ºF T> 50 ºF Mild Moderate Severe Less Temp. Variation More Uniformity More Temp. Variation More Variability 3232

17 Pave-IR TM for thermal profiling Continuous Temperature Measurement Using Infrared Sensor Bars Gives Paver Speed, Idle Time, Position 33 Pave-IR TM for thermal profiling 34

18 Coring for Density & Lab Testing 35 Ground Penetrating Radar AID Integrated Testing Vehicle Courtesy of Advanced Infrastructure Design, Inc. Can GPR provide a reliable estimate of mat density? 36

19 Air Coupled GPR 37 Dielectric Distribution Map Distance from Edge (ft) Distance from Start (ft) LOW dielectric area (estimated HIGH air voids) HIGH dielectric area (estimated LOW air voids) 38

20 5 PERFORMANCE OF THIN OVERLAYS 3939 Performance 1 st Project Before paving Nov., months afer paving 40

21 Performance 1 st Project 45 months after paving months after paving Performance 1 st Project 4242

22 Performance 1 st Project 45 months after paving 4343 Before THMAO 2 nd Project 44

23 Performance 2 nd Project 34 months after paving 4545 Performance 2 nd Project 34 months after paving 4646

24 Performance 3 rd Project 32 months after paving 4747 Performance 3 rd Project 32 months after paving 4848

25 Skid Resistance Results 49 1 st Proj. 70 Friction Improvement Average Skid Number vs. Month of Service Constructed in July Skid Number Months from Construction Data: Courtesy of PennDOT BOMO 5050

26 2 nd Proj. 70 Friction Improvement Average Skid Number vs. Month of Service Constructed in June Skid Number Months from Construction Data: Courtesy of PennDOT BOMO rd Proj 60 Friction Improvement Average Skid Number vs. Month of Service Constructed in September Skid Number Months from Construction Data: Courtesy of PennDOT BOMO 5252

27 Rutting st Proj. Rut Depth (in.) Rutting Average Rut Depth vs. Month of Service SR22 Constructed in July Average Travel 0.02 Average Passing Months from Construction Data: Courtesy of PennDOT BOMO 5454

28 2 nd Proj Rutting Average Rut Depth vs. Month of Service SR230 Constructed in June 2013 Travel Lane Passing Lane Rut Depth (in.) Months from Construction Data: Courtesy of PennDOT BOMO rd Proj. Rut Depth (in.) Rutting Average Rut Depth vs. Month of Service SR220 Constructed in September Average Travel 0.18 Avearage Passing Months from Construction Data: Courtesy of PennDOT BOMO 5656

29 Ride Quality & Smoothness 57 Ride Quality (Smoothness) Improvement Average IRI vs. Month of Service SR st Proj. Constructed in July IRI (in./mile) Average Travel Average Passing Months from Construction Data: Courtesy of PennDOT BOMO 58

30 Ride Quality (Smoothness) Improvement 2 nd Proj. IRI (in./mile) IRI vs. Month of Service SR230-Seg 290 East Travel Lane Constructed in June Months from Construction Data: Courtesy of PennDOT BOMO 59 Left WP Right WP Ride Quality (Smoothness) Improvement 3 rd Proj. IRI (in./mile) IRI vs. Month of Service SR220-Seg 10 North Passing Lane Constructed in September Months from Construction Data: Courtesy of PennDOT BOMO 60 Left WP Right WP

31 Implementation PennDOT Specs Specs approved by FHWA Provisional Spec since August 2017 (C-a00038-A) Standard Spec. Pub 408, Change 4, April Section PennDOT Spec Section 412 (April 2018) Binder o PG 76-22, or PG 64E-22 Aggregate (6.3 mm NMAS) o Fine Aggregate: Uncompacted Void, Sand Equivalent o Course Aggregate(Type A) Abrasion Resistance Flat and Elongated: 10%Max (1:5), and 20% Max (1:3) WMA could be used with Thin Asphalt 6262

32 Recommended Requirements for Design of Asphalt Mix for Thin Lifts AGGREGATE GRADATION REQUIREMENTS, PERCENT PASSING Sieve Size Min. Max. 9.5 mm (3/8 ) 100 Min. 6.3 mm (1/4 ) mm (No. 4) 0-85 Max 2.36 mm (No. 8) m (No. 50) m (No. 200) PennDOT Spec Section 412 (April 2018) Design o 75 Gyrations o VMA: 16.5 o Air Void: o Draindown: 0.3% (Max.) if AC>7.0% 6464

33 Summary Thin Asphalt A Good Tool for Surface Treatment Proper Base Repair is a MUST Improved Ride and Friction Improved Ride and Friction Maintained Minimal Rutting Observed 65 Summary Concerns: Rapid Mat Cooling Reflection of cracks is a challenge on jointed or cracked pavement Advanced Tech for Quality Control: GPR-Density results are promising Thermal Imaging Good Mix Lab Performance: Rutting and Moisture Resistance (HWTD) Crack Resistance (Texas Overly Test) 66

34 Thank You! 67 67