NCHRP 9-43 Mix Design Practices for Warm Mix Asphalt

Transcription

1 NCHRP 9-43 Mix Design Practices for Warm Mix Asphalt Ramon Bonaquist, P.E. Chief Operating Officer Objective To adapt laboratory mixture design and analysis procedures to Compatible with HMA procedures Address wide range of warm mix processes Current Future Acknowledgements Approach Project 9-43 Panel Subcontractors Quality Engineering Solutions University of Massachusetts - Dartmouth University of Wisconsin Madison Western Research Institute Technology Providers Agencies and Contractors Preliminary Focus Revised Phase I Experiments Reheating Binder Grade Short-Term Conditioning Workability Phase II Experiments Expanded Mixing Laboratory Mix Design Field Validation Limited Fatigue Final Draft Appendix to AASHTO R35 Outline Brief Overview of NCHRP Project 9-43 NCHRP Project 9-43 Conclusions NCHRP Project 9-43 Products Review of the Proposed Appendix to AASHTO R35 What to Expect When Using the Appendix Additional Research Major Conclusion 1 can be designed with only minor changes to AASHTO R35 Specimen fabrication procedures Coating and compactability in lieu of viscosity based mixing and compaction temperatures design is challenging for plant foaming process 1

2 Major Conclusion 2 For mixtures using the same aggregates and binders and having binder absorption equal to or less than 1 percent Volumetric properties of and HMA are very similar Supports current practice Compactability, moisture sensitivity, and rutting resistance may be different when designed as compared to HMA Supports need for design procedure Additional Equipment Low Shear Mixer Mechanical Mixer Laboratory Foaming NCHRP 9-43 Products NCHRP Report Recommended Draft Appendix to AASHTO R35, Special Mixture Design Considerations and Methods for Warm Mix Asphalt () Commentary to the Draft Appendix Training Materials for the Draft Appendix NHI Web-Course ~ Oct/Nov 2011 Process Selection mix design requires the producer to select process Planned production temperature Planned compaction temperature Laboratory specimen fabrication Producer should consider Past performance and technical support Cost Useful temperature range Production rates Modifications Equipment for Designing 2. Process Selection 3. Binder Grade Selection 4. in 5. Process Specific Specimen Fabrication s 6. Evaluations Coating Compactability Moisture Sensitivity Rutting Resistance 7. Adjusting the Mixture to Meet Specification Requirements. 9 Binder Grade Selection Use same grade as HMA Low Temeprature Grade Sasobit 47 F LEA 100 F Plant Foam 60 F Evotherm 50 F Advera 47 F High Temperature Grade Change in Grade (HMA Control ), o C 12 2

3 Does Mix at Temperatures Measured to Hirsch Estimated Fully Blended Dynamic Modulus, 68 F, 1.0 Hz HMA 280/255 HMA 248/ / /212 No Short-Term Conditioning Time, hr Specimen Fabrication Short-Term Conditioning 2 hours at Planned Compaction Temperature Compactive Effort and Volumetric Criteria Same as HMA in High temperature grade of <= planned compaction temperature Compaction Temperature, o F RAS Coating Evaluate coating per AASHTO T195 Separate coarse aggregates 9.5 mm sieve for NMAS 12.5 mm and larger 4.75 mm sieve for NMAS 9.5 and smaller Min 200 particles >= 95 percent High Temperature Grade, o C Design Categories Additive Added to the Binder Wet Aggregate Mixtures Additive Added to the Mixture Foamed Asphalt Mixtures 15 Compactability Compact 2 specimens to N design at the planned compaction temperature Compute gyrations to 92 % of Gmm Compact 2 specimens to N design at 30 o C below the planned compaction temperature Compute gyrations to 92 % of Gmm ( N92 ) T 30 Ratio = <= 1.25 ( N ) 92 T 18 3

4 Moisture Sensitivity and Rutting Resistance AASHTO T283 Tensile strength ratio >= 0.80 with no visual stripping Rutting resistance Flow number, AASHTO T79 Traffic Level, Million ESALs Minimum Flow Number <3 NA 3 to < to < Design Binder Content Average Difference in Design Binder Content, wt. % Binder Absorption 0.5 to 1.0 % 22 Adjusting the Mixture to Meet Specifications Coating Compactability Moisture Sensitivity Rutting Resistance Change binder grade Add Increase filler content Decrease VMA Increase N design Consult Technology Supplier Average Difference in Gyration Ratio, % Compactability Without 25 Percent 23 Comparison of HMA and Properties No. N design Mixture Identification Aggregate Absorption HMA A Process B C 1 50 High Yes 320/ / / / Low No 320/ / / / Low Yes 320/ / / / High No 320/ / / / High Yes 320/ / / / Low No 320/ / / /215 Paired t-test -HMA Moisture Sensitivity Average Difference in Tensile Strength Ratio, %

5 Flow Number Average Difference in Flow Number, % Questions Ramon Bonaquist 108 Powers Court, Suite 100 Sterling, VA aatt@erols.com On-Going Research NCHRP 9-47A, Properties and Performance of Warm Mix Asphalt Technologies NCHRP 9-49, Performance of Technologies: Stage I--Moisture Susceptibility NCHRP 9-49A, Performance of Technologies: Stage II--Long-Term Field Performance On-Going Research NCHRP 9-52, Short-Term Laboratory Conditioning of Asphalt Mixtures NCHRP 9-53, Properties of Foamed Asphalt for Warm Mix Asphalt Applications 5