Mix Design Practices for Warm-Mix Asphalt (2011) / Chapter Skim
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Pages 60-63
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From page 60... ...
plant foaming systems. The following unique aspects of WMA mixture design are addressed by the draft appendix to AASHTO R 35: • Process-specific specimen-fabrication procedures, • An evaluation of coating at the planned production temperature, • An evaluation of compactability at the planned field compaction temperature and lower using the Superpave gyratory compactor, and • A check on rutting resistance using the flow number test.
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From page 61... ...
To ensure good mixing of RAP and new binders, the draft appendix to AASHTO R 35 recommends that the planned field compaction temperature for WMA exceed the high-temperature grade of the "as recovered" RAP binder. 4.1.4 Short-Term Oven Conditioning Short-term oven conditioning is included in mixture design to simulate the absorption and aging of the binder that occurs during construction.
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From page 62... ...
This appendix covers the following: • WMA Process Selection, • Binder Grade Selection, • RAP in WMA, • Process-Specific Specimen-Fabrication Procedures, • Evaluation of Coating, • Evaluation of Compactability, • Evaluation of Moisture Sensitivity, • Evaluation of Rutting Resistance, and • Adjusting the Mixture to Meet Specification Requirements. The draft appendix should be used on a trial basis by agencies and producers to provide additional data to further refine the WMA mixture design methods and criteria before being considered for adoption.
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From page 63... ...
The second element of WMA mix design that requires additional research is the development of a short-term conditioning procedure that is applicable to both WMA and HMA for the specimens used to evaluate moisture sensitivity and rutting resistance. Research completed under NCHRP Project 09-43 concluded that 2 h of oven conditioning at the field compaction temperature reasonably reproduces the binder absorption and stiffening that occurs during construction for both WMA and HMA mixtures.
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