Mix Design Practices for Warm-Mix Asphalt (2011) / Chapter Skim
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Appendix A - Draft Appendix to AASHTO R 35: Special Mixture Design Considerations and Methods for Warm Mix Asphalt (WMA)
Appendix A - Draft Appendix to AASHTO R 35: Special Mixture Design Considerations and Methods for Warm Mix Asphalt (WMA)
Pages 66-82
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From page 66... ...
66 A P P E N D I X A Draft Appendix to AASHTO R 35: Special Mixture Design Considerations and Methods for Warm Mix Asphalt (WMA)
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From page 67... ...
SUMMARY 2.1. This appendix includes separate sections addressing the following aspects of WMA mixture design: • Equipment for Designing WMA, • 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.
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From page 68... ...
Laboratory foamed asphalt plant. A laboratory scale foamed asphalt plant capable of producing consistent foamed asphalt at the water content used in field production.
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From page 69... ...
Note 4 – The intermediate and low temperature grade improvements given in Table 1 will allow additional RAP to be used in WMA mixtures when blending chart analyses are used. An approximately 0.6 °C improvement in the low temperature properties will allow approximately 10 percent additional RAP binder to be added to the mixture based on blended binder grade requirements.
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From page 70... ...
Virgin Binder PG Grade 58-28 58-22 64-22 64-16 67-22 Average HMA Production Temperature, oF 285 285 292 292 300 Rate of Improvement of Virgin Binder Low Temperature Grade per oC Reduction in Plant Temperature 0.035 0.025 0.025 0.012 0.025 WMA Production Temperature, oF Recommended Improvement in Virgin Binder Low Temperature Continuous Grade for RAP Blending Chart Analysis, oC 300 NA NA NA NA 0.0 295 NA NA NA NA 0.1 290 NA NA 0.0 0.0 0.1 285 0.0 0.0 0.1 0.0 0.2 280 0.1 0.1 0.2 0.1 0.3 275 0.2 0.1 0.2 0.1 0.3 270 0.3 0.2 0.3 0.1 0.4 265 0.4 0.3 0.4 0.2 0.5 260 0.5 0.3 0.4 0.2 0.6 255 0.6 0.4 0.5 0.2 0.6 250 0.7 0.5 0.6 0.3 0.7 245 0.8 0.6 0.7 0.3 0.8 240 0.9 0.6 0.7 0.3 0.8 235 1.0 0.7 0.8 0.4 0.9 230 1.1 0.8 0.9 0.4 1.0 225 1.2 0.8 0.9 0.4 1.0 220 1.3 0.9 1.0 0.5 1.1 215 1.4 1.0 1.1 0.5 1.2 210 1.5 1.0 1.1 0.5 1.3 7.
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From page 71... ...
Specimen Type Gyratory Specimen Size Approximate Specimen Mass Number Required Maximum Specific Gravity NA 500 to 6,000 g depending on maximum aggregate size 2 per trial blend plus 8 to determine design binder content plus 1 at design binder content for compactability evaluation Volumetric Design 150 mm diameter by 115 mm high 4,700 g 2 per trial blend plus 8 to determine design binder content Coating NA 500 to 6,000 g depending on maximum aggregate size 1 at the design binder content Compactability 150 mm diameter by 115 mm high 4,700 g 4 at the design binder content AASHTO T 283 150 mm diameter by 95 mm high 3,800 g 6 at the design binder content Flow Number 150 mm diameter by 175 mm high 7,000 g 4 at the design binder content 7.1.2. Prepare a batch sheet showing the batch weight of each aggregate fraction, RAP, and the asphalt binder.
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7.3. Preparation of WMA Mixtures With WMA Additives Added to the Binder Note 8 – If specific mixing and storage instructions are provided by the WMA additive supplier, follow the supplier's instructions.
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From page 73... ...
Determine the target total weight of the mixture − = 100 1 newb i t p w w where: wt = target total weight wi = oven dry weight from step 1 newbp = percent by weight of total mix of new binder in the mixture 3. Add new binder to the bowl to reach wt 7.3.2.6.
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From page 74... ...
Note 13 – If the aggregates and RAP have been stored for an extended period of time in a humid environment, then it may be necessary to adjust the weight of binder based on the oven dry weight of the aggregates and RAP as follows: 1. Record the oven dry weight of the aggregates and RAP, w i 2.
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From page 75... ...
Determine the target total weight of the mixture: ( ) − + = 100 1 newb dwfi t p ww w where: wt = target total weight wi = oven dry weight from step 1 wdwf = oven dry weight of the wet fraction from the batch sheet newbp = percent by weight of total mix of new binder in the mixture 3.
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The preparation of foamed asphalt mixtures requires special asphalt binder foaming equipment that can produce foamed asphalt using the amount of moisture that will be used in field production.
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From page 77... ...
This may require producing one batch for the two gyratory specimens and the two maximum specific gravity specimens at each asphalt content then splitting the larger batch into individual samples. Note 18 – If the aggregates and RAP have been stored for an extended period of time in a humid environment, then it may be necessary to adjust the weight of binder based on the oven dry weight of the aggregates and RAP as follows: 1.
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From page 78... ...
Prepare sufficient mixture at the design binder content for 4 gyratory specimens and one maximum specific gravity measurement using the appropriate WMA fabrication procedure from Section 7 of this Appendix including short-term conditioning for 2 hours at the planned compaction temperature.
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Prepare sufficient mixture at the design binder content for 6 gyratory specimens using the appropriate WMA fabrication procedure from Section 7 of this appendix including short-term conditioning.
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8.5.2. Prepare sufficient mixture at the design binder content for four flow number test specimens using the appropriate WMA fabrication procedure from Section 7 of this appendix including short-term conditioning.
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10.1.6. Gyrations to 92 percent relative density for the design binder content at the planned field compaction temperature and 30 °C below the planned field compaction temperature 10.1.7.
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From page 82... ...
10.1.9. Flow number test temperature and the flow number at the design binder content.
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