# AASHTO Designation R 35-12

TS-2d R 35-1 AASHTO Standard Practice for Superpave Volumetric Design for Hot Mix Asphalt (HMA) AASHTO Designation: R 35-12 1. 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 HMA in terms of the air voids, 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 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 purport 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 Standards: 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- μm (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 (G mb ) of Compacted Hot Mix Asphalt (HMA) Using Saturated Surface-Dry Specimens T 195, Determining Degree of Particle Coating of Asphalt Mixtures T 209, Theoretical Maximum Specific Gravity (G mm ) and Density of Hot Mix Asphalt (HMA) T 228, Specific Gravity of Semi-Solid Asphalt Materials T 248, Reducing Samples of Aggregate to Testing Size © 2013 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. Copyright American Association of State Highway and Transportation Officials Provided by IHS under license with AASHTO Licensee=University of Texas Revised Sub Account/5620001114 Not for Resale, 05/28/2014 09:01:01 MDT No reproduction or networking permitted without license from IHS --`,,,`,,,,``,,,,,``,`,,,```,,`-`-`,,`,,`,`,,`---TS-2d R 35-2 AASHTO T 275, Bulk Specific Gravity (G mb ) of Compacted Hot Mix Asphalt (HMA) Using Paraffin- Coated Specimens T 283, Resistance of Compacted Hot Mix Asphalt (HMA) to Moisture-Induced Damage T 312, Preparing and Determining the Density of Hot Mix Asphalt (HMA) 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 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 Design 2.3. Other References: LTPP Seasonal Asphalt Concrete Pavement Temperature Models, LTPPBind 3.1, http://www.ltppbind.com NCHRP Report 567: Volumetric Requirements for Superpave Mix Design 3. TERMINOLOGY 3.1. HMA—hot mix asphalt. 3.2. design ESALs—design equivalent (80 kN) single-axle loads. 3.2.1. Discussion—Design 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 (V a )—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 1—Term defined in Asphalt Institute Manual SP-2, Superpave Mix Design. 3.4. voids in the mineral aggregate (VMA)—the volume of the intergranular 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 (V ba )—the volume of binder absorbed into the aggregate (equal to the difference in aggregate volume when calculated with the bulk specific gravity and effective specific gravity). 3.6. binder content (P b )—the percent by mass of binder in the total mixture, including binder and aggregate. 3.7. effective binder volume (V be )—the volume of binder that is not absorbed into 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). © 2013 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. Copyright American Association of State Highway and Transportation Officials Provided by IHS under license with AASHTO Licensee=University of Texas Revised Sub Account/5620001114 Not for Resale, 05/28/2014 09:01:01 MDT No reproduction or networking permitted without license from IHS --`,,,`,,,,``,,,,,``,`,,,```,,`-`-`,,`,,`,`,,`---TS-2d R 35-3 AASHTO 3.9. dust-to-binder ratio (P 0.075 /P be )—by mass, the ratio between the percent passing the 75- μm (No. 200) sieve (P 0.075 ) and the effective binder content (P be ). 3.10. nominal maximum aggregate size—one size larger than the first sieve that retains more than 10 percent aggregate (Note 2). 3.11. maximum aggregate size—one size larger than the nominal maximum aggregate size (Note 2). Note 2—The 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 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 Selection—Binder, aggregate, and RAP stockpiles 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 3—If RAP is used, the bulk specific gravity of the RAP aggregate may be estimated by determining the theoretical maximum specific gravity (G mm ) 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 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 requirements to account for this error based on experience with local aggregates. 4.2. Design Aggregate Structure—It 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 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 V a , VMA, VFA, dust-to-binder ratio at N design , and relative density at N initial . Note 4—Previous Superpave mix design experience with specific aggregate blends may eliminate the need for three trial blends. 4.3. Design Binder Content Selection—Replicate specimens are compacted in accordance with T 312 at the estimated design binder content and 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 V a , VMA, VFA, and dust-to-binder ratio at N design , and the relative density at N initialand N max . 4.4. Evaluating Moisture Susceptibility—The moisture susceptibility of the design aggregate structure is evaluated at the design binder content: the mixture is conditioned according to the mixture conditioning for the volumetric mixture design procedure in R 30, compacted to 7.0 ± 0.5 percent air voids in accordance with T 312, and evaluated according to T 283. The design shall meet the tensile strength ratio requirement of M 323. © 2013 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. Copyright American Association of State Highway and Transportation Officials Provided by IHS under license with AASHTO Licensee=University of Texas Revised Sub Account/5620001114 Not for Resale, 05/28/2014 09:01:01 MDT No reproduction or networking permitted without license from IHS --`,,,`,,,,``,,,,,``,`,,,```,,`-`-`,,`,,`,`,,`---TS-2d R 35-4 AASHTO 5. SIGNIFICANCE AND USE 5.1. The procedure described in this standard practice is used to produce HMA that satisfies Superpave HMA volumetric mix design requirements. 6. PREPARING AGGREGATE TRIAL BLEND GRADATIONS 6.1. Select a binder in accordance with the 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 5—Each 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 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. 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. Blend the aggregate fractions 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. = 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 controls (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 gradation plot is given in Figure 1. © 2013 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. Copyright American Association of State Highway and Transportation Officials Provided by IHS under license with AASHTO Licensee=University of Texas Revised Sub Account/5620001114 Not for Resale, 05/28/2014 09:01:01 MDT No reproduction or networking permitted without license from IHS --`,,,`,,,,``,,,,,``,`,,,```,,`-`-`,,`,,`,`,,`---TS-2d R 35-5 AASHTO Figure 1—Evaluation of the Gradations of Three Trial Blends (Example) 6.9. Obtain a test specimen from each 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 6—The 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 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 procedure given in Appendix X1 to determine an initial trial binder content for each trial aggregate blend gradation. Note 7—When 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 blend gradations. From Table 1, determine the number of gyrations based on the design ESALs for the project. Note 8—At 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 of 110 to 120 mm for aggregates with combined bulk specific gravities of 2.55 to 2.70, respectively. © 2013 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law. Copyright American Association of State Highway and Transportation Officials Provided by IHS under license with AASHTO Licensee=University of Texas Revised Sub Account/5620001114 Not for Resale, 05/28/2014 09:01:01 MDT No reproduction or networking permitted without license from IHS --`,,,`,,,,``,,,,,``,`,,,```,,`-`-`,,`,,`,`,,`---TS-2d R 35-6 AASHTO 8.2. Condition the mixtures according to R 30, and compact the specimens to N designgyrations in accordance with T 312. Record the specimen height to the nearest 0.1 mm after each revolution. 8.3. Determine the bulk specific gravity (G mb ) of each of the compacted specimens in accordance with T 166 or T 275 as appropriate. Table 1—Superpave Gyratory Compaction Effort Design ESALs a (million) Compaction Parameters Typical Roadway Application bN initialN designN max 0.3 6 50 75 Applications include roadways with very light traffic volumes, such as local roads, county roads, and city streets where truck traffic is prohibited or at a very minimal level. Traffic on these roadways would be considered local in nature, not regional, intrastate, or interstate. Special purpose roadways serving recreational sites or areas may also be applicable to this level. 0.3 to 3 7 75