1、Standard Practice for Materials Selection and Mixture Design of Permeable Friction Courses (PFCs) AASHTO Designation: PP 77-141American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2d PP 77-1 AASHTO Standard Practice for
2、 Materials Selection and Mixture Design of Permeable Friction Courses (PFCs) AASHTO Designation: PP 77-1411. SCOPE 1.1. This standard covers the materials requirements and mix design of permeable friction course (PFC) asphalt mixtures. 1.2. This standard may involve hazardous materials, operations a
3、nd equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED
4、 DOCUMENTS 2.1. AASHTO Standards: M 156, Requirements for Mixing Plants for Hot-Mixed, Hot-Laid Bituminous Paving Mixtures M 231, Weighing Devices Used in the Testing of Materials M 320, Performance-Graded Asphalt Binder R 30, Mixture Conditioning of Hot Mix Asphalt (HMA) T 19M/T 19, Bulk Density (“
5、Unit Weight”) and Voids in Aggregate T 85, Specific Gravity and Absorption of Coarse Aggregate T 96, Resistance to Degradation of Small-Size Coarse Aggregate by Abrasion and Impact in the Los Angeles Machine T 104, Soundness of Aggregate by Use of Sodium Sulfate or Magnesium Sulfate T 176, Plastic F
6、ines in Graded Aggregates and Soils by Use of the Sand Equivalent Test T 209, Theoretical Maximum Specific Gravity (Gmm) and Density of Hot Mix Asphalt (HMA) T 245, Resistance to Plastic Flow of Asphalt Mixtures Using Marshall Apparatus T 283, Resistance of Compacted Asphalt Mixtures to Moisture-Ind
7、uced Damage T 304, Uncompacted Void Content of Fine Aggregate T 305, Determination of Draindown Characteristics in Uncompacted Asphalt Mixtures T 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor T 326, Uncompacted Void Content of Co
8、arse Aggregate (As Influenced by Particle Shape, Surface Texture, and Grading) T 331, Bulk Specific Gravity (Gmb) and Density of Compacted Hot Mix Asphalt (HMA) Using Automatic Vacuum Sealing Method TP 108, Abrasion Loss of Asphalt Mixture Specimens 2015 by the American Association of State Highway
9、and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d PP 77-2 AASHTO 2.2. ASTM Standards: D3549/D3549, Standard Test Method for Thickness or Height of Compacted Bituminous Paving Mixture Specimens D4791, Standard Test Method for Flat Particles, Elongate
10、d Particles, or Flat and Elongated Particles in Coarse Aggregate 3. TERMINOLOGY 3.1. Definitions: 3.1.1. asphalt binderan asphalt-based cement that is produced from petroleum residue either with or without the addition of modifiers. 3.1.2. abrasion lossthe loss of mass from an asphalt mixture specim
11、en under the effect of abrasion. 3.1.3. air voidsthe total volume of the small pockets of air between the coated aggregate particles throughout a compacted paving mixture, expressed as a percent of the total volume of the compacted specimen. 3.1.4. breakpoint sievethe finest sieve to retain at least
12、 10 percent of the aggregate fraction. 3.1.5. draindownseparation of asphalt binder from the coarse aggregate structure, generally during storage or transportation. 3.1.6. permeable friction course (PFC)a special type of porous asphalt mixture with air voids of at least 18 percent used for reducing
13、hydroplaning and potential for loss of friction resistance, where the function of the mixture is to provide a free-draining layer that permits surface water to migrate laterally through the mixture to the edge of the pavement. 3.1.7. stabilizing additivematerials used to minimize draindown of asphal
14、t during transport and placement of PFC, which may include fibers, polymers, crumb rubber, or a combination of these additives. 3.1.8. voids in the coarse aggregate (VCA)the volume of voids between the coarse aggregate particles, where this volume includes filler, fine aggregate, air voids, asphalt
15、binder, and stabilizing additives, if used. 4. SUMMARY OF PRACTICE 4.1. Aggregates, asphalt binder, and stabilizing additives are selected that meet specification values. Trial aggregate blend gradations are selected and tested to determine the design aggregate gradation. The blends are compacted us
16、ing a trial binder content in order to evaluate the trial mixes and select the design gradation to ensure stone-on-stone contact. Once a trial gradation is selected, the asphalt binder content is altered and the optimum asphalt binder content is selected based on meeting minimum binder content and a
17、ir void requirements and ensuring stone-on-stone contact in the mixture. Stone-on-stone content is verified by ensuring the volume of voids in the mixture is less than or equal to the volume of voids in the dry-rodded coarse aggregate fraction of the design gradation. The mix design is further verif
18、ied by determining the abrasion loss, which is used as an indicator of the durability of the mixture. The designed mixture is then evaluated for resistance to moisture susceptibility. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a
19、 violation of applicable law.TS-2d PP 77-3 AASHTO 5. SIGNIFICANCE AND USE 5.1. The procedure described in this practice is used to select materials and design permeable friction course mixtures that will provide good performance in terms of permeability and durability when subjected to high volumes
20、of traffic. 6. MATERIALS SELECTION 6.1. Select coarse aggregates, fine aggregates, asphalt binder, and stabilizing additives as follows. 6.1.1. Coarse AggregatesSelect coarse aggregate(s) meeting the requirements in Table 1. Table 1Coarse Aggregate Quality Requirements for PFC Mixtures Test Method S
21、pec. Minimum Spec. Maximum Los Angeles Abrasion, % lossaT 96 30 Flat or elongated, %, 5 to 1 ASTM D4791 10 Soundness (5 Cycles), % loss T 104 Sodium sulfate 10 Magnesium sulfate 15 Uncompacted voids, % T 326, Method A 45 aAggregates with LA Abrasion loss values up to 52 percent have been used succes
22、sfully to produce PFC mixtures, however, when the LA Abrasion value exceeds approximately 30 percent, excessive breakdown may occur in the laboratory compaction process or during in-place compaction. 6.1.2. Fine AggregatesSelect fine aggregate(s) to meet the requirements in Table 2. Table 2Fine Aggr
23、egate Quality Requirements for PFC Mixtures Test Method Spec. Minimum Spec. Maximum Soundness (5 cycles), % loss T 104 Sodium sulfate 10 Magnesium sulfate 15 Uncompacted voids, % T 304, Method A 45 Sand equivalency, % T 176 50 6.1.3. Asphalt BindersPerformance-graded asphalt binders meeting the requ
24、irements of M 320 are selected based on the climate and traffic. Because of the relatively high binder contents and open grading of the aggregate, a stiff asphalt binder is needed to ensure durability. Therefore, for high-volume roadways or pavements with slow to standing traffic, select the asphalt
25、 binder high-temperature grade two grades higher than the asphalt binder grade required for the climate. (See Note 1.) Select the high-temperature binder grade one grade higher than the climatic grade for all other roadways. Note 1Some southern states successfully use a PG 76 asphalt binder for high
26、-volume roadways, which is only one grade higher. 6.1.4. Stabilizing AdditivesStabilizing additives are needed to prevent draindown of asphalt binder from the coarse aggregate skeleton during transportation and placement. Stabilizing additives such as cellulose fiber, mineral fiber, crumb rubber, an
27、d polymers have been used to minimize draindown potential. 6.1.5. Design GradationIn order to provide the high level of permeability desirable with permeable friction courses, an aggregate gradation having a very open gradation is needed. Table 3 includes the specific gradation ranges. 2015 by the A
28、merican Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d PP 77-4 AASHTO Table 3PFC Gradation Specification Bands Sieve Size Nominal Maximum Aggregate Size% Passing 9.5 mm (3/8in.) PFC 12.5 mm (1/2in.) PFC 19.0 mm (3/4in
29、.) PFC Min Max Min Max Min Max 25 mm (1 in.) 100 19 mm (3/4in.) 100 85 100 12.5 mm (1/2in.) 100 80 100 55 70 9.5 mm (3/8in.) 85 100 35 60 4.75 mm (No. 4) 20 30 10 25 10 25 2.36 mm (No. 8) 5 15 5 10 5 10 0.075 mm (No. 200) 0 4 0 4 0 4 7. MIX DESIGN PROCEDURE 7.1. The mixture design procedure requires
30、 determining the voids in the coarse aggregate (VCA) fraction of each trial gradation, selecting a trial asphalt binder content, mixing and compacting samples of each trial, and analyzing the trials to select the design gradation. Once the design gradation is selected, the binder content is optimize
31、d. 7.2. Preparing Trial Blends: 7.2.1. Selection of Trial GradationsSelect at least three initial trial gradations to fall within one of the master specification ranges shown in Table 3. The trial gradations should typically fall along the coarse and fine limits of the gradation range, with another
32、falling in the middle of the range. These trial gradations are obtained by adjusting the amount of fine and coarse aggregates in each blend. 7.2.2. Determination of VCA in the Coarse Aggregate FractionDetermine the void content of the coarse aggregate fraction in the dry-rodded condition according t
33、o T 19M/T 19. Designate this as VCADRC. At the same time, determine and record the bulk density of the coarse aggregate in the dry rodded condition, M. Divide M by the density of water at 25C (77F) to obtain the bulk specific gravity of the coarse aggregate fraction, Gca. 7.2.3. Selection of Trial A
34、sphalt ContentThe minimum desired asphalt binder content (by mass of the mixture) to provide a sufficient volume of asphalt binder for permeable friction courses is shown in Table 4. For PFCs with aggregates having a combined bulk specific gravity less than or equal to 2.75, a trial asphalt binder c
35、ontent of between 6 and 6.5 percent is recommended. If the combined aggregate bulk specific gravity exceeds 2.75, the trial binder content may be reduced slightly. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applic
36、able law.TS-2d PP 77-5 AASHTO Table 4Minimum Asphalt Content Requirements for PFC Mixtures with Varying Bulk Specific Gravities Combined Aggregate Bulk Specific Gravity Minimum Asphalt Content, % 2.40 6.8 2.45 6.7 2.50 6.6 2.55 6.5 2.60 6.3 2.65 6.2 2.70 6.1 2.75 6.0 2.80 5.9 2.85 5.8 2.90 5.7 2.95
37、5.6 3.00 5.5 7.3. Preparation of Trial Blend Specimens: 7.3.1. Prepare AggregatesDry the aggregates to be used in the mixture to a constant mass and separate by dry-sieving into individual size fractions. The following size fractions are recommended: 19.0 to 12.5 mm (3/4to 1/2in.) 12.5 to 9.5 mm (1/
38、2to 3/8in.) 9.5 to 4.75 mm (3/8in to No. 4) 4.75 to 2.36 mm (No. 4 to No. 8) Passing 2.36 mm (No. 8), if 2.36 mm is breakpoint sieve 2.36 to 1.18 mm (No. 8 to No. 16), if 1.18 mm is breakpoint sieve Passing 1.18 mm (No. 16), if 1.18 mm is breakpoint sieve 7.3.2. Number of Samples per Trial BlendPrep
39、are a total of four samples of each trial blend mixture; three samples for determining the air void content of compacted specimens and one sample for determining the theoretical maximum specific gravity according to T 209. 7.3.3. Determine the mixing and compaction temperatures in accordance with T
40、245, Section 3.3.1. The mixing temperature shall be the temperature needed to produce an asphalt binder viscosity of 170 20 cSt. The compaction temperature shall be the temperature required to provide an asphalt binder viscosity of 280 30 cSt. The selected temperatures may need to be changed for mod
41、ified asphalt binders; in such a case, follow the binder suppliers guidelines for mixing and compaction temperatures. 7.3.4. For each test specimen, weigh into a pan the appropriate amount of each size fraction to produce the required sample size. Mix the aggregates in each pan and place in an oven
42、set to a temperature no more than 28C (50F) above the mixing temperature determined in Section 7.3.3. 7.3.5. Heat the asphalt binder to the mixing temperature determined in Section 7.3.3. 7.3.6. When preparing PFC in the laboratory, use a mechanical mixing apparatus. Place the heated aggregate batch
43、 into the mechanical mixing container. Add the required amounts of asphalt binder and any stabilizing additive into the container. Mix the aggregate, asphalt binder, and stabilizing additives rapidly until thoroughly coated. Mixing times for PFC should be slightly longer than for conventional mixtur
44、es to ensure that the stabilizing additives are thoroughly dispersed within the mixture. After mixing, short-term age the PFC mixture in accordance with R 30. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable
45、law.TS-2d PP 77-6 AASHTO Note 2Dry-mixing fibers, if used, into the aggregate before adding the asphalt binder has been found to help disperse the fibers uniformly throughout the mixture. 7.3.7. Sample CompactionCompact three individual specimens of each trial blend at the established compaction tem
46、perature using 50 revolutions of the Superpave gyratory compactor in accordance with T 312. Note 3More than 50 revolutions should not be used; PFC is relatively easy to compact in the laboratory and exceeding this compactive effort can cause excessive aggregate breakdown. 7.3.8. After the samples ha
47、ve been compacted and are stable enough to prevent damage, extrude them from the molds and allow them to cool. Determine the bulk specific gravity of each specimen using T 331 or by dimensional analysis. To use dimensional analysis, determine and record the dry mass of each specimen in grams. Determ
48、ine and record the height of each specimen in centimeters in accordance with ASTM E3549/D3549M using calibrated calipers. Determine the diameter of each specimen in centimeters as the average of four equally spaced measurements using the calibrated calipers. Calculate the area of the specimen using
49、the average diameter, A = d2/4. Calculate the volume of the specimen by multiplying the specimen area by its average height. Calculate the bulk density of the specimen by dividing the dry mass of the specimen by the calculated volume. Convert the bulk density into the bulk specific gravity, Gmb, by dividing by 0.99707 g/cm3, the density of water at 25C (77F). 7.3.9. Determine the theoretical maximum specific gravity, Gmm, of the un
