AASHTO M 325-08 (2017). Standard Specification for Stone Matrix Asphalt (SMA)

Prévia do material em texto

Scanned by CamScanner
Standard Specification for 
Stone Matrix Asphalt (SMA) 
AASHTO Designation: M 325-08 (2012)1 
1. 
1.1. 
1.2. , , 
1.3. 
1.4. 
2. 
2.1. 
" ,I 
2.2. 
TS-2d'/ 
SCOPE 
This sp~cificati~n covers the design of Stone Matrix Asphalt (SMA) using the Superpave gyratory 
compacto~ (SGC). The SMA design is based on the volumetric properties of the SMA in terms of 
air voids (Va), the voids in mineral aggregat~ (VMA), and the presence of stone-on-stone contact. 
This standard specifies minimum quality,requirements for asphalt binder, aggregate, mineral filler, 
. and stabilizing additives for SMA mixture, designs. 
The values stated in SI units are to be regarded as the standard. The U.S. Customary units in 
parentheses are for information only. ' 
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 prior to use. 
REFERENCED DOCUMENTS 
AASHTO Standards: 
• 
• 
• 
• 
• '. • 
• ,. . ' 
• 
M 320, Performance-Graded Asphalt Binder 
M 323, Superpave Volumetric Mix Design 
R 46, Designing Stone Matrix Aspbalt (SMA) 
T 85, Specific Gravity and Absorption of Coarse Aggregate 
T 89, Determining the Liquid Limit of Soils 
T 90, Determining 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 
r 104, Soundness of Aggregate by Use of Sodium Sulfate or Magnesium Sulfate 
T 283, Resistance of Compacted Asphalt Mixtures to Moistljre-Ind,uced pamage 
T 305, Determination of Drain down Characteristics in Uncompacted Asphalt Mixtures 
T 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of the 
Superpave Gyratory Compactor 
• r , 
ASTM Standards: 
: i,' 
• D 4791, Standard Test M~thod ~or Flat P~icles, Elongated Particles, or, Flat and Elongated 
Particles in Coarse Aggregate 
• D 5821, Standard Test Meth04 for DeteQll.ining tl)e Percentage of Fractured Particles in 
Coarse Aggregate 
• J L iJ J 'p- , " I ,I 
M 325-10 MSHTO 
i . 
'I' , I ~ , i 
!! 
Scanned by CamScanner
2.3. A h I I . 4G ' J sp a t nstitute Publication: ' \ 
• MS-2, Mix Design Methods/or Asphalt Concrete and Other Hot-Mix Types 
2.4. " 
National Asphalt Pavement Association publication: 
• IS 127, Evaluation o/Baghouse Fines/or Hot Mix Asphalt 
, 
~3-.------~T=E=R~M~IN-O-L-O-G-Y----------------------~" --~------
3.1. 
3.2. 
3.3. 
3.4. 
3.5. 
3.6. 
4. 
4.1. 
5. 
5.1. 
6. 
6.1. 
6 .1.1. 
6.1.2. 
stone matrix asphalt (SMA)-a hot mix 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 that fraction of the aggregate retained on the 
4 .75-mm (No. 4) sieve but may be designated as other sizes. . 
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 I). 
Note 1-Term defined in the Asphalt Institute Publication MS-2 . 
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 I) . 
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). 
SMA mortar-a mixture of asphalt binder, filler [material pass~g the 0.075-mm (No. 200) sieve], 
and stabilizing additive. 
stabilizing additive-either cellulose or mineral fiber. 
SIGNIFICANCE AND USE 
This standard may be used for designing and evaluating material and mixture properties for SMA. 
ASPHALT BINDER REQUIREMENTS 
The asphalt binder shall be a performance grade meeting the requirements ofM 320, which is 
appropriate for the clll~ate and traffic-Ioa.ding conditions at the site of the paving project. 
Guidance for the selectIon of the appropnate asphalt binder is provided in M 323. 
AGGREGATE REQUIREMENTS 
Aggregates used in SMA shall conform to the requirements listed below. 
Coarse Aggregale-Coarse aggregates shall be 100 percent crushed and conform to the quality 
requirements of Table I. . 
Fine Aggregate-Fine aggregates shall be 100 percent crushed and conform to the quality 
requirements of Table 2. 
-------------------------------------.~~~----------------------------~~~ TS-2d ' M 325-2, AA5HTO 
Scanned by CamScanner
Table 1-Coarse Aggregate Quality Requirements , 
Test Method Maximum 
Los,Ahgeles (L.A.) abrasion, T96 - 30" 0/0 loss 
Flat and elongated, %' 3 to I 04791 20 
5 to I 04791 5 
Absorption, percent T85 2.0 
Soundness (5 Cycles), %' T 104 
Sodium sulfate or 15 
Magnesium sulfate 20 
Crushed content, % 05821 
One face 100 
Two face 90 
Aggre~ales with higher L.A. abr~sion values have been used successfully to produce SMA mix.es. However, when the L.A. abrasion exceeds 30, 
excesSIve breakdown may occur m the laboratory compaction process or during in-place compaction. 
Flat and elongated criteria apply to the design aggregate blend. 
Sodium sulfate or magnesium sulfate may be used. It is not a requirement to perfonn both methods. 
Table 2-Fine Aggregate Quality Requirements 
Test Method Minimum Maximum 
Soundness (5 cycles), %" 
Sodium sulfate or 
Magnesium sulfate 
Liquid limit, % 
T 104 
T89 
15 
20 
25 
Plasticity index, % T90 Nonplastic 
Sodium sulfate or magnesium sulfate may be used. It is not a requirement to perform both methods. 
7. 
7.1. 
8. 
8.1. 
.\ 
TS-2d 
MINERAL FILLER 
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 impurities and have a plasticity index not 
greater than four. 
Note 2-It 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. 
STABILIZING ADDITIVE 
A 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 
mi.xture mass 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 3-Ifthe draindown from.the plant-produced samples exceeds the draindown from 
laboratory-prepared samples, the quantity of the stabilizer should be increased. To maximize 
durabilit}: '(thro).lgh binder volume), fibers also can be added regardless of draindown. 
\ ' 
' .. 
M 325-3 AASHTO 
,I 
j 
Scanned by CamScanner
o---~~~~~~~~-------------___ 
9. SMA DESIGN REQUIREMENTS 
9.1. h adation requirements of Table 3. When the b Ik 
The combined aggregates shall conform. to I e gr d ' the mixture vary by more than 0.2 hU 
specific gravities of the different stockpIles to be use. In . ' t e 
. d th lumetnc percentage. trIal blend gradations shall be base on e vo . 
Table 3--SMA Gradation Specification Bands 
Sieve, 
mm 
(in.) 
25.0mm 
(1 in.) 
19.0 mm 
('I, in.) 
12.5mm 
(II, in.) 
9.5mm 
(,I, in.) 
4.75 mm 
(No.4) 
2.36 mm 
(No.8) 
1.18 mm 
(No. 16) 
0.60mm 
(No. 30) 
0.30mm 
(No. 50) 
0.075mm 
(No. 200) 
9.2 . 
Air voids, % 
VMA,% 
VCAMlx,% 
TSR 
Nominal-Maximum Aggregate Size 
19 mm el. in.) 12.5 mm (1/2 in.) 
Lower Upper Lower Upper 
100 
90 100 100 
50 88 90 100 
25 60 50 80 
20 28 20 35 
16 24 16 24 
8.0 11.0 8.0 11.0 
The designed SMA mixture shall meet the requirements of Table 4. 
Property Requirement 
4.0 (Nole 4) 
17.0 min 
Less than VeAn,c (Note 6) 
0.80 min 
--9.5 nun ela in.) -Lower Uppe;---
100 
70 95 
30 50 
20 30 
21 
18 
IS 
8.0 12.0 
Draindown at production temperature, % 0.3 max 
Asphalt binder content, % 6.0 min (Note 7) 
SMA Mixture Specifications refer to specimens compacted in accordance with T 312 at 100 gyrations (Note 5). 
TS-2d 
Note 4-For low-traffic-volume 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 5--When aggregates have a Los Angeles abrasion loss value greater than 30 percent, the 
desirable number of SGC design gyrations is 75. 
Note 6-See R 46 for instructions on calculating VCAMIX and VCADRC• 
Note 7-Experience 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. Whe~ an 
SMA mix cannot be designed within the minimum binder content requirements of Table 4 ustIlg 
the available aggregates, refer to the guidance given on Ihis issue in R 46. 
M 325-4 
Scanned by CamScanner
p 
9.3. The tensile strength ratio (TSR) of the SMA shall be at leas~ O.~O, 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 e; ceed 0.3 percent. .. 
1 Formerly AASHTO Provisional Standard MP 8. First published as a full standard in 2008. . . 
,. \ ,. . 
" . 
. , . 
" 
" I. 
TS-2d M 325-5 AASHTO 
I 
.1 
! 
• 'I! 
I, , 
.' l' 
\ 
" , , 
" 'I 
I' 
" I,