National Superpave Status Present & Future

Transcription

1 National Superpave Status Present & Future John R. Bukowski Federal Highway Administration Northeast Asphalt User/Producer Group October 23, 2003 US Department of Transportation Federal Highway Administration

2 Superpave 2003 Asphalt Binder Implementation Status Implemented In Progress Undetermined

3 Superpave 2003 Mix Design Implementation Status Implemented In Progress Undetermined

4 Common Mix Issues VMA Difficult to Achieve VMA Too High Compaction Level Asphalt Content Moisture Susceptibility Test Permeability Rut Test Strength Test No. of States

5 Volumetrics Superpave N design Requirements Just Right 52% No Experience 4% Too Low 11% Too High 33%

6 Volumetrics Asphalt Content: Superpave vs Conventional Mix 40 Number of States Lower Than Conventional Similar Not Sure

7 Need for a Accelerated Rut Test 50 Number of States Needed Not Needed Not sure

8 Construction Openness of Superpave Mixes Number of States High Acceptable Not sure

9 The Superpave System Superpave is in place and it does work There is a great deal of work needed to fill gaps in the system Work is continuing to fill the gaps A plan is in place to complete the system by 2005

10 Superpave Long Range Plan Goal 1: Mix design completed by 2003 Recommended binder type and mixture based on Anticipated environment Loading conditions Layer location

11 Superpave Long Range Plan Goal 2: Performance predictions available by 2005 Predict the ability of a mix to withstand rutting, fatigue, thermal cracking, and moisture damage through a series of laboratory tests and mechanistic models.

12 Superpave Long Range Plan Goal 3: Integrate binder and mix requirements into a performance- based quality control (QC) system during construction by 2005

13 Superpave Long Range Plan Goal 4: Superpave to be fully understood Public and private-sector engineers Technicians Contractors Through continuing training and outreach programs by 2005

14 Superpave System Binder specification Mix design Models System

15 Superpave: Future for Binders Superpave Plus Specifications

16 Why Superpave Plus Specs The existing specifications do not identify the performance characteristics of modified binders The existing specifications do not have a criteria for fatigue of durability Agencies look to other tests to identify modifiers

17 Superpave Plus Specifications Most of tests used today by agencies to identify modified binders are not performance related Forced Ductility (FD), Elastic Recovery (ER), and Toughness and Tenacity (TT) do not relate to performance

18 State DOT s Specifying Polymer PG (PG+) Ductility ER ER Ductility, TT & ER TT & DT ER & TT ER ER & FD ER & Ductility ER ER ER ER ER SB/SBS Required PG + modifier PG ER ER SB/SBS Required FD & ER ER ER & PA PA PA ER-Elastic Recovery FD-Force Ductility TT-Toughness & Tenacity PA-Phase Angle

19 Understanding the Performance of Modified Asphalt in Mixes NCHRP funded study performed by FHWA for evaluation of: Effects of several typicallyused polymer modifiers on mix performance Modifier Scale Up Air Blown (*) Elvaloy SBS lg SBS l SBS rg EVA EVA g 74-32

20 Superpave: Future for Mixtures

21 Gyratory Comparisons

22 Internal Angle Measurement Factors Influencing Angle of Gyration SGC Frame Compliance SGC Maintenance SGC Mold Wear Mixture Stiffness

23 SGC Internal Angle Superpave ETG / ASTM Task Group(s): AASHTO T312 AASHTO DAV Specification PP48 Improved Internal Angle Measurement

24 Internal Rapid Angle Measurement

25 Hot-Mix Simulator (HMS) e r Eccentric loading on a wedge with angle θ L HMS 115 mm DAV H Mold F*tan θ F e

26 Aggregate Imaging System Captures coarse & fine aggregate properties Shape Angularity Texture (coarse agg) Potential use for aggregate QC or input to mix design

27 Superpave Performance Tester Used for providing input to mechanistic pavement Potential as Pass/Fail test or Quality Verification for asphalt mixes

28 Background Superpave Performance Test (SPT) Equipment part of NCHRP protocol testing Two first-article prototype devices evaluated Interlaken Shedworks

29 Dynamic Modulus (E*) Yields Input into Structural Design in 2002 Design Guide Addresses Rutting and Cracking Static Creep (flow time) Test Equipment Simple to Use Minimal Training Repeated Load (flow number) May be Best Simulation of Actual Load

30 Asphalt Construction Lab/Field Tools New Gsb,, Moisture Superpave Gyratory Compactor angle kit (DAV) Aggregate Imaging System (AIMS) Innovative Contracting Performance Related Specs (PRS) Warranty Construction

31 NCHRP 1-37(A) 1 New Pavement Design Guide Develop and deliver a guide for design of new and rehabilitated pavement structures - Based on mechanistic-empirical empirical principles - Accompanied by the necessary computational software - For adoption and distribution by AASHTO

32 Proposed Pavement Design Guide TRAFFIC ENVIRONMENT MATERIALS PERFORMANCE CRITERIA MODELS THICKNESS

33 NCHRP 9-33: A Mix Design Manual for Hot Mix Asphalt Update the 1993 method and manual: Superpave performance test(s) As-delivered 2002 design guide performance models and software Spreadsheets for volumetric design, performance testing, and design optimization. (RFP Issue: End 2003)

34 Asphalt Today and Tomorrow AASHTO New Pavement Design Guide On track validation required (NCHRP) Superpave System Binder specification - modifiers? Mix Design Superpave Performance Tester Models System framework on track Construction Practices Tools: New Gsb,, Moisture, SGC angle kit... Contracting: PRS framework, Warranty

35 Thank you for your attention!