image-asphalt texture

STANDARD SPECIFICATIONS
Stone Matrix Asphalt (SMA)

AASHTO M 325-08

Standard Specifications for Aggregates

Stone Matrix Asphalt (SMA)

Standard AASHTO M 325-08

AASHTO M 325-08 specification covers the design of Stone Matrix Asphalt (SMA) using the Superpave gyratory compactor (SGC), based on the volumetric properties of the SMA in terms of air voids (Va), voids in mineral aggregate (VMA), and the presence of stone-on-stone contact.

Stone Matrix Asphalt (SMA)

Hot Mix Asphalt (HMA) consisting of a coarse aggregate skeleton with coarse aggregate-on-coarse aggregate contact (stone-on-stone contact) and a rich asphalt binder mortar. 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)

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.

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.

Voids in the Coarse Aggregate (VCA)

The volume between the coarse aggregate particles, which includes the volume of filler, fine aggregate, air voids, asphalt binder, and stabilizing additive (if used).

SMA Mortar

A mixture of asphalt binder, filler (material passing the 0.075-mm (No. 200) sieve), and stabilizing additive.

Stabilizing Additive

Either cellulose or mineral fiber.


The asphalt binder shall be a performance grade meeting the requirements of AASHTO M 320. The selected binder shall be appropriate for the climate and traffic-loading conditions at the site of the paving project.


Coarse Aggregate

Coarse aggregates shall be 100 percent crushed and conform to the quality requirements given in table below.

Test Method Minimum Maximum
Los Angeles (L.A.) abrasion,% loss AASHTO T 96 --- ---
Flat and Elongated, % (3:1) ASTM D 4791 --- 20
Flat and Elongated, % (5:1) ASTM D 4791 --- 5
Absorption, % AASHTO T 85 --- 2.0
Soundness (5 cycles), Sodium Sulfate AASHTO T 104 --- 15
Soundness (5 cycles), Magnesium Sulfate AASHTO T 104 --- 20
Crushed Content, one face ASTM D 5821 100 ---
Crushed Content, two face ASTM D 5821 90 ---

Fine Aggregate

Fine aggregate shall be 100 percent crushed and conform to the quality requirements given in table below.

Test Method Minimum Maximum
Liquid Limit, % AASHTO T 89 --- 25
Plasticity Index AASHTO T 90 Non Plastic Non Plastic
Soundness (5 cycles), Sodium Sulfate AASHTO T 104 --- 15
Soundness (5 cycles), Magnesium Sulfate AASHTO T 104 --- 20

Mineral Filler

Mineral filler shall consist of finely divided mineral matter such as crusher fines and fly ash. Filler shall be free from organic impurities and have a plasticity index not greater than four. Mineral fillers with modified Rigden voids higher than 50 percent not be used in SMA.

Stabilizing Additive

A stabilizer such as cellulose or mineral fiber will be added to the mixture to prevent draindown. For cellulose fibers, a dosage rate of approximately 0.3 percent or more by total mixture mass. For mineral fibers, a dosage rate of approximately 0.4 percent by total mixture mass is adopted. The maximum draindown shall be limited to 0.3 percent by weight of the mix when held at the plant temperature for 1 h.

Combined Aggregate Grading

The combined aggregates shall conform to the gradation requirements as given in the input table.


SMA Mixture Specifications for Superpave Gyratory Compactor are given in table below (for specimens compacted in accordance with AASHTO T 312 at 100 gyrations).

Property Requirement
Air Voids, % 4.0
VMA, % (3:1) 17.0, min
VCAmix less than VCADRC
Tensile Strength Ratio (TSR) 0.80, min
Draindown at production temperature, % 0.3%, max
Asphalt Binder Content, % 6.0, min

Input - Project & Sample Details

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SMA Gradation Specification Bands: Input Table

Sieve Size, mm Perc. Passing
Sample
19 mm nominal size
UL
19 mm nominal size
LL
12.5 mm nominal size
UL
12.5 mm nominal size
LL
9.5 mm nominal size
UL
9.5 mm nominal size
LL
25.0 100
19.0 100 90 100
12.5 88 50 100 90 100
9.5 60 25 80 50 95 70
4.75 28 20 35 20 50 30
2.36 24 16 24 16 30 20
1.18 21
0.600 18
0.300 15
0.075 11 8 11 8 12 8

PARTICLE SIZE GRADING COMPARISON - CHART

0.45 POWER CHART



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