1、Standard Specification for Stone Matrix Asphalt (SMA) AASHTO Designation: M 325-08 (2012)1American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2d M 325-1 AASHTO Standard Specification for Stone Matrix Asphalt (SMA) AASH
2、TO Designation: M 325-08 (2012)11. SCOPE 1.1. This specification covers the design of Stone Matrix Asphalt (SMA) using the Superpave gyratory compactor (SGC). The SMA design is based on the volumetric properties of the SMA in terms of air voids (Va), the voids in mineral aggregate (VMA), and the pre
3、sence of stone-on-stone contact. 1.2. This standard specifies minimum quality requirements for asphalt binder, aggregate, mineral filler, and stabilizing additives for SMA mixture designs. 1.3. The values stated in SI units are to be regarded as the standard. The U.S. Customary units in parentheses
4、are for information only. 1.4. This standard 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 standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations p
5、rior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 320, Performance-Graded Asphalt Binder M 323, Superpave Volumetric Mix Design R 46, Designing Stone Matrix Asphalt (SMA) T 85, Specific Gravity and Absorption of Coarse Aggregate T 89, Determining the Liquid Limit of Soils T 90, Determini
6、ng the Plastic Limit and Plasticity Index of Soils 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 283, Resistance of Compacted Asphalt Mixtures to Moisture-
7、Induced Damage 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 2.2. ASTM Standards: D4791, Standard Test Method for Flat Particles, Elongated Parti
8、cles, or Flat and Elongated Particles in Coarse Aggregate D5821, Standard Test Method for Determining the Percentage of Fractured Particles in Coarse Aggregate 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable
9、 law.TS-2d M 325-2 AASHTO 2.3. Asphalt Institute Publication: MS-2, Mix Design Methods for Asphalt Concrete and Other Hot-Mix Types 2.4. National Asphalt Pavement Association Publication: IS 127, Evaluation of Baghouse Fines for Hot Mix Asphalt 3. TERMINOLOGY 3.1. stone matrix asphalt (SMA)a hot mix
10、 asphalt (HMA) consisting of two parts, a coarse aggregate skeleton and a rich asphalt binder mortar. The mixture must have an aggregate skeleton with coarse aggregate-on-coarse aggregate contact (generally referred to as stone-on-stone contact). The coarse aggregate is generally considered to be th
11、at fraction of the aggregate retained on the 4.75-mm (No. 4) sieve but may be designated as other sizes. 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 comp
12、acted paving mixture (Note 1). Note 1Term defined in the Asphalt Institute Publication MS-2. 3.3. 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,
13、 expressed as a percent of the total volume of the specimen (Note 1). 3.4. voids in the coarse aggregate (VCA)the volume between the coarse aggregate particles. This volume includes filler, fine aggregate, air voids, asphalt binder, and stabilizing additive (if used). 3.5. SMA mortara mixture of asp
14、halt binder, filler material passing the 0.075-mm (No. 200) sieve, and stabilizing additive. 3.6. stabilizing additiveeither cellulose or mineral fiber. 4. SIGNIFICANCE AND USE 4.1. This standard may be used for designing and evaluating material and mixture properties for SMA. 5. ASPHALT BINDER REQU
15、IREMENTS 5.1. The asphalt binder shall be a performance grade meeting the requirements of M 320, which is appropriate for the climate and traffic-loading conditions at the site of the paving project. Guidance for the selection of the appropriate asphalt binder is provided in M 323. 6. AGGREGATE REQU
16、IREMENTS 6.1. Aggregates used in SMA shall conform to the requirements listed below. 6.1.1. Coarse AggregateCoarse aggregates shall be 100 percent crushed and conform to the quality requirements of Table 1. 6.1.2. Fine AggregateFine aggregates shall be 100 percent crushed and conform to the quality
17、requirements of Table 2. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d M 325-3 AASHTO Table 1Coarse Aggregate Quality Requirements Test Method Minimum Maximum Los Angeles (L.A.) abrasion, % loss
18、T 96 30aFlat and elongated, %b 3 to 1 ASTM D4791 205 to 1 ASTM D4791 5 Absorption, percent T 85 2.0 Soundness (5 cycles), %cT 104 Sodium sulfate or 15 Magnesium sulfate 20 Crushed content, % ASTM D5821 One face 100 Two face 90 aAggregates with higher L.A. abrasion values have been used successfully
19、to produce SMA mixes. However, when the L.A. abrasion exceeds 30, excessive breakdown may occur in the laboratory compaction process or during in-place compaction. bFlat and elongated criteria apply to the design aggregate blend. cSodium sulfate or magnesium sulfate may be used. It is not a requirem
20、ent to perform both methods. Table 2Fine Aggregate Quality Requirements Test Method Minimum Maximum Soundness (5 cycles), %aT 104 Sodium sulfate or 15 Magnesium sulfate 20 Liquid limit, % T 89 25 Plasticity index, % T 90 Nonplastic aSodium sulfate or magnesium sulfate may be used. It is not a requir
21、ement to perform both methods. 7. MINERAL FILLER 7.1. Mineral filler shall consist of finely divided mineral matter such as crusher fines and fly ash. At the time of use, it should be sufficiently dry to flow freely and essentially free from agglomerations. Filler shall be free from organic impuriti
22、es and have a plasticity index not greater than four. Note 2It is recommended that mineral fillers with modified Rigden voids (IS 127) higher than 50 percent not be used in SMA. Experience has shown that fillers exceeding 50 percent excessively stiffen the SMA mortar. 8. STABILIZING ADDITIVE 8.1. A
23、stabilizer such as cellulose or mineral fiber will be added to the mixture. The dosage rate for cellulose shall be approximately 0.3 percent or more by total mixture mass and sufficient to prevent draindown. For mineral fibers, the dosage rate shall be approximately 0.4 percent by total mixture mass
24、 and sufficient to prevent draindown. The maximum draindown will be 0.3 percent by weight of the mix when held at the plant temperature for 1 h. Note 3If the draindown from the plant-produced samples exceeds the draindown from laboratory-prepared samples, the quantity of the stabilizer should be inc
25、reased. To maximize durability (through binder volume), fibers also can be added regardless of draindown. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d M 325-4 AASHTO 9. SMA DESIGN REQUIREMENTS 9
26、.1. The combined aggregates shall conform to the gradation requirements of Table 3. When the bulk specific gravities of the different stockpiles to be used in the mixture vary by more than 0.2, the trial blend gradations shall be based on the volumetric percentage. Table 3SMA Gradation Specification
27、 Bands Sieve, mm (in.) Nominal-Maximum Aggregate Size 19 mm (3/4in.) 12.5 mm (1/2in.) 9.5 mm (3/8in.) Lower Upper Lower Upper Lower Upper 25.0 mm (1 in.) 100 19.0 mm (3/4in.) 90 100 100 12.5 mm (1/2in.) 50 88 90 100 100 9.5 mm (3/8in.) 25 60 50 80 70 95 4.75 mm (No. 4) 20 28 20 35 30 50 2.36 mm (No.
28、 8) 16 24 16 24 20 30 1.18 mm (No. 16) 21 0.60 mm (No. 30) 18 0.30 mm (No. 50) 15 0.075 mm (No. 200) 8.0 11.0 8.0 11.0 8.0 12.0 9.2. The designed SMA mixture shall meet the requirements of Table 4. Table 4SMA Mixture Specifications for Superpave Gyratory CompactoraProperty Requirement Air voids, % 4
29、.0 (Note 4) VMA, % 17.0 min VCAMIX, % Less than VCADRC(Note 6) TSR 0.80 min Draindown at production temperature, % 0.3 max Asphalt binder content, % 6.0 min (Note 7) aSMA Mixture Specifications refer to specimens compacted in accordance with T 312 at 100 gyrations (Note 5). Note 4For low-traffic-vol
30、ume roadways or colder climates, target air void contents less than 4.0 percent can be used, but should not be less than 3.0 percent. Note 5When aggregates have a Los Angeles abrasion loss value greater than 30 percent, the desirable number of SGC design gyrations is 75. Note 6See R 46 for instructi
31、ons on calculating VCAMIXand VCADRC. Note 7Experience has shown that binder contents should be from 6.0 to 7.0 percent. Lowering the binder content below 6.0 percent can detrimentally affect the durability of the SMA. When an SMA mix cannot be designed within the minimum binder content requirements
32、of Table 4 using the available aggregates, refer to the guidance given on this issue in R 46. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2d M 325-5 AASHTO 9.3. The tensile strength ratio (TSR) of
33、 the SMA shall be at least 0.80, at 6.0 1.0 percent air voids, when tested in accordance with T 283. 9.4. Draindown sensitivity shall be determined on the SMA mixture in accordance with T 305 at the anticipated plant-production temperature and shall not exceed 0.3 percent. 1Formerly AASHTO Provisional Standard MP 8. First published as a full standard in 2008. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
