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From page 28... ... Given that viscosity-based mixing and compaction temperatures are not applicable to many WMA processes, the planned production and compaction temperatures are used in the WMA mixture design process to evaluate coating and the compactability/workability of the WMA. It should be emphasized that the optimal production and compaction temperatures are different for the various WMA processes and should be carefully considered when selecting production and compaction temperatures to be used in the WMA design process. Read the entire page →
From page 29... ... C-2 Special Mixture Design Considerations and Methods for Warm Mix Asphalt Step Description Major WMA Differences 1 Gather Information 1. WMA process, 2. Read the entire page →
From page 30... ... RAP binders typically range from PG 82 to PG 100, resulting in corresponding minimum WMA compaction temperatures ranging II. Commentary on Special Mixture Design Considerations and Methods for Warm Mix Asphalt (WMA) Read the entire page →
From page 31... ... Table 4 summarizes the optimum binder C-4 Special Mixture Design Considerations and Methods for Warm Mix Asphalt 0.00 0.20 0.40 0.60 0.80 1.00 1.20 0.0 0.5 1.0 1.5 2.0 2.5 Conditioning Time, Hours A ve ra ge R at io o f M ea su re d M od ul us to Es tim at ed F ul ly B le nd ed M od ul us Control 255 Control 230 Advera 230 Advera 212 Evotherm 230 Evotherm 212 Sasobit 230 Sasobit 212 Figure 1. Comparison of the ratios of measured to fully blended dynamic moduli. Read the entire page →
From page 32... ... In this study, the Evotherm mixtures do not have higher optimum binder contents than the HMA or the other WMA processes, suggesting that the RAP and new binder do mix in Evotherm mixtures and that the differences shown in Figure 15 for this process are due to the extraction and recovery process used in the mixing study. Plant mixing studies similar to the NCHRP 9-43 laboratory mixing study are needed to confirm that RAP and new binders mix at WMA process temperatures for field conditions. Read the entire page →
From page 33... ... 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 LowTemperature 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 LowTemperature 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 1.3 205 1.6 1.1 1.2 0.6 1.3 200 1.7 1.2 1.3 0.6 1.4 Table 5. Recommended improvement in virgin binder low-temperature continuous grade for RAP blending chart analysis for WMA production temperatures. Read the entire page →
From page 34... ... II. Commentary on Special Mixture Design Considerations and Methods for Warm Mix Asphalt (WMA) Read the entire page →
From page 35... ... t d s n d = ⎛⎝⎜ ⎞⎠⎟ C-8 Special Mixture Design Considerations and Methods for Warm Mix Asphalt No. Mixture Identification Mixing/Compaction Temperature, °F,for Process: Ndesign Aggregate Water Absorption, % RAP HMA AdveraWMA Evotherm 3G WMA Sasobit WMA 1 50 1.5 Yes 320/310 225/215 225/215 270/260 2 50 0.8 No 320/310 270/260 270/260 225/215 3 75 1.0 Yes 320/310 270/260 225/215 270/260 4 75 1.6 No 320/310 225/215 270/260 225/215 5 100 1.2 Yes 320/310 270/260 270/260 225/215 6 100 1.3 No 320/310 225/215 225/215 270/260 Table 6. Read the entire page →
From page 36... ... Average difference in design binder content (WMA-HMA) from the NCHRP 9-43 mix design study (error bars are ± 95% one-sided confidence intervals) Read the entire page →
From page 37... ... The amount of additive needed may be specified by the WMA process supplier as percent by weight of binder or total C-10 Special Mixture Design Considerations and Methods for Warm Mix Asphalt Step Description HMA WMA Comment 1 Calculate batch weights X X Must calculate WMA additive content for some processes 2 Batch aggregates X X Must batch WMA additive for some processes 3 Heat aggregates and asphalt binder X X Use planned production temperature for WMA 4 Mix aggregates and binder X X Procedure is WMA process specific 5 Short-term oven conditioning X X WMA uses lower temperature. 6 Compact laboratory specimens X X WMA uses lower temperature 7 Calculate volumetric composition of laboratory specimens X X 8 Adjust aggregate proportions to meet volumetric requirements X X 9 Evaluate coating and compactability NA X Used in WMA design in place of viscositybased mixing and compaction temperatures 10 Conduct performance testing X X Moisture sensitivity for all mixtures, rutting resistance for design traffic levels of 3 m ESALs or greater Table 7. Read the entire page →
From page 38... ... Laboratory specimens are mixed at the planned production temperature, and coating is evaluated to determine the acceptability of the WMA process. Process-Specific Specimen Fabrication Procedures For mixture design, the various WMA processes were grouped into four generic categories: 1. Read the entire page →
From page 39... ... , represents the stiffening that occurs during construction and some short time in service. C-12 Special Mixture Design Considerations and Methods for Warm Mix Asphalt 2.300 2.400 2.500 2.600 CO I-70 Control CO I-70 Advera CO I-70 Evotherm CO I-70 Sasobit YNP Control YNP Advera YNP Sasobit PA SR2007 Control PA SR2007 Evotherm PA SR2006 Control PA SR2006 Advera PA SR2006 Gencor PA SR2006 LEA PA SR2006 Sasobit Monroe NC Astec Maximum Specific Gravity M ix tu re /P ro ce ss Compaction Temp 2 Hours Field Mix Figure 5. Read the entire page →
From page 40... ... Until additional research is conducted to develop appropriate mixing times for bucket mixers, technicians and engineers will have to develop mixing times for their WMA mixtures based on coating evaluations for HMA mixtures produced using the traditional viscosity-based mixing temperatures. Read the entire page →
From page 41... ... The criterion for AASHTO T 283 is the same as that for HMA. C-14 Special Mixture Design Considerations and Methods for Warm Mix Asphalt 0 50 100 150 200 250 300 350 400 450 300 250 190 150 Temperature, F To rq ue , i nlb Control Advera Sasobit Figure 7. Read the entire page →
From page 42... ... Of the nine WMA mixtures that used a WMA process that included an antistrip additive, the tensile strength ratio remained the same or improved in 67% of the mixtures. For WMA mixtures produced using processes that do not include antistrip additives, the tensile strength ratio never improved and decreased in 79% of the mixtures. Read the entire page →
From page 43... ... The additional information for WMA is that needed in Step 1 of the mix design process: C-16 Special Mixture Design Considerations and Methods for Warm Mix Asphalt Process Number Average Difference in Compaction Temperature, F Average Difference in Flow Number, % Advera 3 -46.7 -39 Evotherm 2 -50.0 -38 LEA 1 -80.0 -50 Sasobit 3 -48.3 +38 Table 9. Summary of average difference in flow number of WMA compared to HMA for the NCHRP 9-43 field validation sections. Read the entire page →
From page 44... ... II. Commentary on Special Mixture Design Considerations and Methods for Warm Mix Asphalt (WMA) Read the entire page →

From page 28...

... Given that viscosity-based mixing and compaction temperatures are not applicable to many WMA processes, the planned production and compaction temperatures are used in the WMA mixture design process to evaluate coating and the compactability/workability of the WMA. It should be emphasized that the optimal production and compaction temperatures are different for the various WMA processes and should be carefully considered when selecting production and compaction temperatures to be used in the WMA design process.