1、Standard Practice for Superpave Volumetric Design for Asphalt Mixtures AASHTO Designation: R 35-171 Technical Section: 2d, Proportioning of AsphaltAggregate Mixtures Release: Group 3 (August 2017) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite
2、 249 Washington, D.C. 20001 TS-2d R 35-1 AASHTO Standard Practice for Superpave Volumetric Design for Asphalt Mixtures AASHTO Designation: R 35-171Technical Section: 2d, Proportioning of AsphaltAggregate Mixtures Release: Group 3 (August 2017) 1. SCOPE 1.1. This standard practice for mix design eval
3、uation uses aggregate and mixture properties to produce a hot mix asphalt (HMA) job mix formula. The mix design is based on the volumetric properties of the asphalt mixture in terms of the air voids, voids in the mineral aggregate (VMA), and voids filled with asphalt (VFA). 1.2. This standard practi
4、ce may also be used to provide a preliminary selection of mix parameters as a starting point for mix analysis and performance prediction analyses that primarily use T 320 and T 322. 1.3. Special mixture design considerations and practices to be used in conjunction with this standard practice for the
5、 volumetric design of Warm Mix Asphalt (WMA) are given in Appendix X2. 1.4. This standard practice may involve hazardous materials, operations, and equipment. This standard practice does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of t
6、he user of this procedure to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 320, Performance-Graded Asphalt Binder M 323, Superpave Volumetric Mix Design R 83, Preparation of C
7、ylindrical Performance Test Specimens Using the Superpave Gyratory Compactor (SGC) R 30, Mixture Conditioning of Hot Mix Asphalt (HMA) R 76, Reducing Samples of Aggregate to Testing Size T 2, Sampling of Aggregates T 11, Materials Finer Than 75-m (No. 200) Sieve in Mineral Aggregates by Washing T 27
8、, Sieve Analysis of Fine and Coarse Aggregates T 84, Specific Gravity and Absorption of Fine Aggregate T 85, Specific Gravity and Absorption of Coarse Aggregate T 100, Specific Gravity of Soils 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Dupli
9、cation is a violation of applicable law.TS-2d R 35-2 AASHTO T 166, Bulk Specific Gravity (Gmb) of Compacted Asphalt Mixtures Using Saturated Surface-Dry Specimens T 195, Determining Degree of Particle Coating of Asphalt Mixtures T 209, Theoretical Maximum Specific Gravity (Gmm) and Density of Hot Mi
10、x Asphalt (HMA) T 228, Specific Gravity of Semi-Solid Asphalt Materials T 275, Bulk Specific Gravity (Gmb) of Compacted Asphalt Mixtures Using Paraffin-Coated Specimens T 283, Resistance of Compacted Asphalt Mixtures to Moisture-Induced Damage T 312, Preparing and Determining the Density of Asphalt
11、Mixture Specimens by Means of the Superpave Gyratory Compactor T 320, Determining the Permanent Shear Strain and Stiffness of Asphalt Mixtures Using the Superpave Shear Tester (SST) T 322, Determining the Creep Compliance and Strength of Hot Mix Asphalt (HMA) Using the Indirect Tensile Test Device T
12、 324, Hamburg Wheel-Track Testing of Compacted Asphalt Mixtures T 378, Determining the Dynamic Modulus and Flow Number for Asphalt Mixtures Using the Asphalt Mixture Performance Tester (AMPT) 2.2. Asphalt Institute Standard: SP-2, Superpave Mix Design 2.3. Other References: LTPP Seasonal Asphalt Con
13、crete Pavement Temperature Models, LTPPBind 3.1, http:/ NCHRP Report 567: Volumetric Requirements for Superpave Mix Design 3. TERMINOLOGY 3.1. absorbed binder volume (Vba)the volume of binder absorbed into the aggregate (equal to the difference in aggregate volume when calculated with the bulk speci
14、fic gravity and effective specific gravity). 3.2. air voids (Va)the total volume of the small pockets of air between the coated aggregate particles throughout a compacted paving mixture, expressed as a percent of the bulk volume of the compacted paving mixture (Note 1). Note 1Term defined in Asphalt
15、 Institute Manual SP-2, Superpave Mix Design. 3.3. binder content (Pb)the percent by mass of binder in the total mixture, including binder and aggregate. 3.4. design ESALsdesign equivalent (80 kN) single-axle loads. 3.4.1. discussiondesign ESALs are the anticipated project traffic level expected on
16、the design lane over a 20-year period. For pavements designed for more or less than 20 years, determine the design ESALs for 20 years when using this standard practice. 3.5. dust-to-binder ratio (P0.075/Pbe)by mass, the ratio between the percent passing the 75-m (No. 200) sieve (P0.075) and the effe
17、ctive binder content (Pbe). 3.6. effective binder volume (Vbe)the volume of binder that is not absorbed into the aggregate. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2d R 35-3 AASHTO 3.7. HMAho
18、t mix asphalt. 3.8. maximum aggregate sizeone size larger than the nominal maximum aggregate size (Note 2). Note 2The definitions given in Sections 3.10 and 3.11 apply to Superpave mixes only and differ from the definitions published in other AASHTO standards. 3.9. nominal maximum aggregate sizeone
19、size larger than the first sieve that retains more than 10 percent aggregate (Note 2). 3.10. primary control sieve (PCS)the sieve defining the break point between fine and coarse-graded mixtures for each nominal maximum aggregate size. 3.11. reclaimed asphalt pavement (RAP)removed and/or processed p
20、avement materials containing asphalt binder and aggregate. 3.12. voids filled with asphalt (VFA)the percentage of the VMA filled with binder (the effective binder volume divided by the VMA). 3.13. voids in the mineral aggregate (VMA)the volume of the intergranular void space between the aggregate pa
21、rticles of a compacted paving mixture that includes the air voids and the effective binder content, expressed as a percent of the total volume of the specimen (Note 1). 4. SUMMARY OF THE PRACTICE 4.1. Materials SelectionBinder, aggregate, and RAP stockpiles are selected that meet the environmental a
22、nd traffic requirements applicable to the paving project. The bulk specific gravity of all aggregates proposed for blending and the specific gravity of the binder are determined. Note 3If RAP is used, the bulk specific gravity of the RAP aggregate may be estimated by determining the theoretical maxi
23、mum specific gravity (Gmm) of the RAP mixture and using an assumed asphalt absorption for the RAP aggregate to back-calculate the RAP aggregate bulk specific gravity, if the absorption can be estimated with confidence. The RAP aggregate effective specific gravity may be used in lieu of the bulk spec
24、ific gravity at the discretion of the agency. The use of the effective specific gravity may introduce an error into the combined aggregate bulk specific gravity and subsequent VMA calculations. The agency may choose to specify adjustments to the VMA requirements to account for this error based on ex
25、perience with local aggregates. 4.2. Design Aggregate StructureIt is recommended that at least three trial aggregate blend gradations from selected aggregate stockpiles are blended. For each trial gradation, an initial trial binder content is determined, and at least two specimens are compacted in a
26、ccordance with T 312. A design aggregate structure and an estimated design binder content are selected on the basis of satisfactory conformance of a trial gradation meeting the requirements given in M 323 for Va, VMA, VFA, dust-to-binder ratio at Ndesign, and relative density at Ninitial. Note 4Prev
27、ious Superpave mix design experience with specific aggregate blends may eliminate the need for three trial blends. 4.3. Design Binder Content SelectionReplicate specimens are compacted in accordance with T 312 at the estimated design binder content and at the estimated design binder content 0.5 perc
28、ent and +1.0 percent. The design binder content is selected on the basis of satisfactory conformance with the requirements of M 323 for Va, VMA, VFA, and dust-to-binder ratio at Ndesign, and the relative density at Ninitialand Nmax. 4.4. Evaluating Moisture SusceptibilityEvaluate the moisture suscep
29、tibility of the design aggregate structure at the design binder content. Oven-condition the mixture according to T 283 Section 6. Compact specimens to 7.0 0.5 percent air voids according to T 312. Group, moisture-condition, 2017 by the American Association of State Highway and Transportation Officia
30、ls. All rights reserved. Duplication is a violation of applicable law.TS-2d R 35-4 AASHTO test, and evaluate specimens according to T 283. The design shall meet the tensile strength ratio requirement of M 323. 5. SIGNIFICANCE AND USE 5.1. The procedure described in this standard practice is used to
31、produce asphalt mixtures that satisfy Superpave asphalt volumetric mix design requirements. 6. PREPARING AGGREGATE TRIAL BLEND GRADATIONS 6.1. Select a binder in accordance with the requirements of M 323 and 320. 6.2. Determine the specific gravity of the binder according to T 228. 6.3. Obtain sampl
32、es of aggregates proposed to be used for the project from the aggregate stockpiles in accordance with T 2. Note 5Each stockpile usually contains a given size of an aggregate fraction. Most projects employ three to five stockpiles to generate a combined gradation conforming to the job-mix formula and
33、 M 323. 6.4. Reduce the samples of aggregate fractions according to R 76 to samples of the size specified in T 27. 6.5. Wash and grade each aggregate sample according to T 11 and T 27 for the purpose of materials characterization of the aggregates. 6.6. Determine the bulk and apparent specific gravi
34、ty for each coarse and fine aggregate fraction in accordance with T 85 and T 84, respectively, and determine the specific gravity of the mineral filler in accordance with T 100. 6.7. Blend the aggregate fractions for design purposes using Equation 1: P = Aa + Bb + Cc, etc. (1) where: P = percentage
35、of material passing a given sieve for the combined aggregates A, B, C, etc.; A, B, C, etc. = percentage of material passing a given sieve for aggregates A, B, C, etc.; and a, b, c, etc. = proportions of aggregates A, B, C, etc., used in the combination, and where the total = 1.00. 6.8. Prepare a min
36、imum of three trial aggregate blend gradations; plot the gradation of each trial blend on a 0.45-power gradation analysis chart, and confirm that each trial blend meets M 323 gradation controls (see Table 4 of M 323). Gradation control is based on four control sieve sizes: the sieve for the maximum
37、aggregate size, the sieve for the nominal maximum aggregate size, the 4.75- or 2.36-mm sieve, and the 0.075-mm sieve. An example of three acceptable trial blends in the form of a gradation plot is given in Figure 1. 2017 by the American Association of State Highway and Transportation Officials. All
38、rights reserved. Duplication is a violation of applicable law.TS-2d R 35-5 AASHTO Figure 1Evaluation of the Gradations of Three Trial Blends (Example) 6.9. Obtain a test specimen from each of the trial blends according to R 76, and conduct the quality tests specified in Section 6 of M 323 to confirm
39、 that the aggregate in the trial blends meets the minimum quality requirements specified in M 323. Note 6The designer has an option of performing the quality tests on each stockpile instead of the trial aggregate blend. The test results from each stockpile can be used to estimate the results for a g
40、iven combination of materials. 7. DETERMINING AN INITIAL TRIAL BINDER CONTENT FOR EACH TRIAL AGGREGATE GRADATION 7.1. Designers can either use their experience with the materials or the procedure given in Appendix X1 to determine an initial trial binder content for each trial aggregate blend gradati
41、on. Note 7When using RAP, the initial trial asphalt content should be reduced by an amount equal to that provided by the RAP. 8. COMPACTING SPECIMENS OF EACH TRIAL GRADATION 8.1. Prepare replicate mixtures (Note 8) at the initial trial binder content for each of the chosen trial aggregate trial blen
42、d gradations. From Table 1, determine the number of gyrations based on the design ESALs for the project. Note 8At least two replicate specimens are required, but three or more may be prepared if desired. Generally, 4500 to 4700 g of aggregate is sufficient for each compacted specimen with a height o
43、f 110 to 120 mm for aggregates with combined bulk specific gravities of 2.55 to 2.70, respectively. 8.2. Condition the mixtures according to R 30, and compact the specimens to Ndesigngyrations in accordance with T 312. Record the specimen height to the nearest 0.1 mm after each revolution. 2017 by t
44、he American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2d R 35-6 AASHTO 8.3. Determine the bulk specific gravity (Gmb) of each of the compacted specimens in accordance with T 166 or T 275 as appropriate. Table 1Supe
45、rpave Gyratory Compaction Effort Design ESALsa (Million) Compaction Parameters Typical Roadway ApplicationbNinitialNdesignNmax(6) ( )0.1 if 4.0aaVMA V V = (7) Note 13A change in binder content affects the VMA through a change in the bulk specific gravity of the compacted specimen (Gmb). 9.3.4. Calcu
46、late the VMA for each aggregate trial blend at Ndesigngyrations and 4.0 percent air voids using Equation 8: design trialVMA VMA VMA= + (8) where: VMAdesign= VMA estimated at a design air void content of 4.0 percent; and VMAtrial= VMA determined at the initial trial binder content. 9.3.5. Using the v
47、alues of Vadetermined in Section 9.3.1 and Equation 9, estimate the relative density of each specimen at Ninitialwhen the design air void content is adjusted to 4.0 percent at Ndesign: nitial% 100imb dmm amm iGhGVGh= (9) where: nitial%immG = relative density at Ninitialgyrations at the adjusted desi
48、gn binder content; hd= height of the specimen after Ndesigngyrations, from the Superpave gyratory compactor, mm; and hi= height of the specimen after Ninitialgyrations, from the Superpave gyratory compactor, mm. 2017 by the American Association of State Highway and Transportation Officials. All righ
49、ts reserved. Duplication is a violation of applicable law.TS-2d R 35-8 AASHTO 9.3.6. Calculate the effective specific gravity of the aggregate (Gse), the estimated percent of effective binder (estbeP ), and the estimated dust-to-binder ratio (P0.075/Pbe) for each trial blend using Equations 10, 11, and 12: 100100bsebmm bPGPGG=(10) ( )( )( )est estse sbbe s b bse sbGGP PG PGG= +(11) where: estbeP = estimated effective binder content; Ps= aggregate content,
