1、Standard Practice for Superpave Volumetric Design for Asphalt Mixtures AASHTO Designation: R 35-151American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2d R 35-1 AASHTO Standard Practice for Superpave Volumetric Design
2、for Asphalt Mixtures AASHTO Designation: R 35-1511. SCOPE 1.1. This standard practice for mix design evaluation 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 vo
3、ids, voids in the mineral aggregate (VMA), and voids filled with asphalt (VFA). 1.2. This standard practice 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
4、mixture design considerations and practices to be used in conjunction with this standard practice for the 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 purp
5、ort to address all of the safety concerns, if any, associated with its use. It is the responsibility of the 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 Standard
6、s: M 320, Performance-Graded Asphalt Binder M 323, Superpave Volumetric Mix Design PP 60, Preparation of Cylindrical Performance Test Specimens Using the Superpave Gyratory Compactor (SGC) R 30, Mixture Conditioning of Hot Mix Asphalt (HMA) T 2, Sampling of Aggregates T 11, Materials Finer Than 75-m
7、 (No. 200) Sieve in Mineral Aggregates by Washing T 27, 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 T 166, Bulk Specific Gravity (Gmb) of Compacted Hot
8、Mix Asphalt (HMA) 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 Mix Asphalt (HMA) T 228, Specific Gravity of Semi-Solid Asphalt Materials T 248, Reducing Samples of Aggregat
9、e to Testing Size 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d R 35-2 AASHTO T 275, Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Paraffin-Coated Specimens T 283, Resistan
10、ce of Compacted Asphalt Mixtures to Moisture-Induced Damage T 312, Preparing and Determining the Density of Asphalt 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
11、322, Determining the Creep Compliance and Strength of Hot Mix Asphalt (HMA) Using the Indirect Tensile Test Device TP 79, 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 Desi
12、gn 2.3. Other References: LTPP Seasonal Asphalt Concrete Pavement Temperature Models, LTPPBind 3.1, http:/ NCHRP Report 567: Volumetric Requirements for Superpave Mix Design 3. TERMINOLOGY 3.1. HMAhot mix asphalt. 3.2. design ESALsdesign equivalent (80 kN) single-axle loads. 3.2.1. discussiondesign
13、ESALs are the anticipated project traffic level expected on 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. 3.3. air voids (Va)the total volume of the small pockets of air between
14、 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 Institute Manual SP-2, Superpave Mix Design. 3.4. voids in the mineral aggregate (VMA)the volume of the intergranul
15、ar void space between the aggregate particles 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). 3.5. absorbed binder volume (Vba)the volume of binder absorbed into the aggregate (equal to t
16、he difference in aggregate volume when calculated with the bulk specific gravity and effective specific gravity). 3.6. binder content (Pb)the percent by mass of binder in the total mixture, including binder and aggregate. 3.7. effective binder volume (Vbe)the volume of binder that is not absorbed in
17、to the aggregate. 3.8. voids filled with asphalt (VFA)the percentage of the VMA filled with binder (the effective binder volume divided by the VMA). 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d
18、R 35-3 AASHTO 3.9. 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 effective binder content (Pbe). 3.10. nominal maximum aggregate sizeone size larger than the first sieve that retains more than 10 percent aggregate (Note 2).
19、3.11. 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. 3.12. reclaimed asphalt pavement (RAP)removed and/or
20、processed pavement materials containing asphalt binder and aggregate. 3.13. primary control sieve (PCS)the sieve defining the break point between fine and coarse-graded mixtures for each nominal maximum aggregate size. 4. SUMMARY OF THE PRACTICE 4.1. Materials SelectionBinder, aggregate, and RAP sto
21、ckpiles are selected that meet the environmental and 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 ma
22、y be estimated by determining the theoretical maximum 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 spe
23、cific gravity may be used in lieu of the bulk specific 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
24、requirements to account for this error based on experience 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 determi
25、ned, and at least two specimens are compacted in accordance 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 Nde
26、sign, and relative density at Ninitial. Note 4Previous 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 a
27、nd at the estimated design binder content 0.5 percent 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 M
28、oisture Susceptibility Evaluate the moisture susceptibility of the design aggregate structure at the design binder content. Oven-condition the mixture according to the Mixture Conditioning for Volumetric Mixture Design procedure in R 30, Section 7.1. Compact specimens to 7.0 0.5 percent air voids ac
29、cording to T 312. Group, moisture-condition, test, and evaluate specimens according to T 283. The design shall meet the tensile strength ratio requirement of M 323. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of appli
30、cable law.TS-2d R 35-4 AASHTO 5. SIGNIFICANCE AND USE 5.1. The procedure described in this standard practice is used to 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 th
31、e requirements of M 323. 6.2. Determine the specific gravity of the binder according to T 228. 6.3. Obtain samples 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
32、 projects employ three to five stockpiles to generate a combined gradation conforming to the job-mix formula and M 323. 6.4. Reduce the samples of aggregate fractions according to T 248 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
33、 the purpose of materials characterization of the aggregates. 6.6. Determine the bulk and apparent specific gravity 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. Blen
34、d the aggregate fractions for design purposes using Equation 1: P = Aa + Bb + Cc, etc. (1) where: P = percentage 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. =
35、 proportions of aggregates A, B, C, etc., used in the combination, and where the total = 1.00. 6.8. Prepare a minimum 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 co
36、ntrols (see Table 3 of M 323). Gradation control is based on four control sieve sizes: the sieve for the maximum 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 gradatio
37、n plot is given in Figure 1. 2015 by the American Association of State Highway and Transportation Officials.All 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
38、 of the trial blends according to T 248, and conduct the quality tests specified in Section 6 of M 323 to confirm 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 inste
39、ad of the trial aggregate blend. The test results from each stockpile can be used to estimate the results for a given 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 p
40、rocedure given in Appendix X1 to determine an initial trial binder content for each trial aggregate blend gradation. 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
41、replicate mixtures (Note 8) at the initial trial binder content for each of the chosen trial aggregate trial blend 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 prep
42、ared if desired. Generally, 4500 to 4700 g of aggregate is sufficient for each compacted specimen with a height of 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 Ndesigngyra
43、tions in accordance with T 312. Record the specimen height to the nearest 0.1 mm after each revolution. 2015 by the 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 specifi
44、c gravity (Gmb) of each of the compacted specimens in accordance with T 166 or T 275 as appropriate. Table 1Superpave 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 con
45、tent affects the VMA through a change in the bulk specific gravity of the compacted specimen (Gmb). 9.3.4. Calculate 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 v
46、oid content of 4.0 percent; and VMAtrial= VMA determined at the initial trial binder content. 9.3.5. Using the values 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: ini
47、tial% 100mb dmm amm iGhGVGh= (9) where: initial%mmG = relative density at Ninitialgyrations at the adjusted design 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
48、gyratory compactor, mm. 2015 by the American Association of State Highway and Transportation Officials.All rights 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 bind
49、er ()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, percent by mass of total mixture; Gb= specific gravity of the binder; Gse= effective specific gravity of the combined aggregate; Gsb= bulk specific gravity of the combined aggregate; and estbP
