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MATERIAL TESTING
Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Saturated Surface-Dry Specimens

AASHTO T 166-13

Standard Method of Tests

Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Saturated Surface-Dry Specimens

Standard AASHTO T 166-13

Bulk specific gravity (Gmb) of compacted hot mix asphalt (HMA) specimens is determined based on AASHTO T 166-13 test method.

This method is not applicable to HMA samples that contain open or interconnecting voids or absorb more than 2.0 percent of water by volume. In such cases AASHTO T 275 or AASHTO T 331 should be used.
Bulk Specific Gravity (of solids) (Gmb) is the ratio of the mass in air of a unit volume of a permeable material (including both permeable and impermeable voids normal to the material) at a stated temperature to the mass in air of equal density of an equal volume of gas-free distilled water at a stated temperature.

The test specimens for the test may be either laboratory-compacted HMA or sampled from HMA pavements. The size of the specimen shall be such that;
(1) the diameter of cylindrically compacted or cored specimens, or the length of the sides of sawed specimens, be at least equal to four times the maximum size of the aggregate; and
(2) the thickness of specimens be at least one and one-half times the maximum size of the aggregate.

Three methods are specified for the determination of Gmb;
(a) Method A - using suspension apparatus to enable weighing of specimen under water.
(b) Method B - using Volumeter.
(c) Method C (Rapid Test) - for specimen that are not required to be saved and containing substantial amount of moisture (including specimens obtained by coring or sawing).

Method B is not applicable for specimens that have more than 6 percent air voids.

This TransCalc calculation tool can be used to calculate the bulk specific gravity and absorption as per Method A.

Apparatus:

Weigh Device - conforming to AASHTO M 231, readable to 0.1 percent of the sample mass or better, and equipped with a suitable suspension apparatus.

Suspension Apparatus - enabling weighing of specimen in water.

Water Bath - For immersing the specimen in water while suspended under the weighing device, equipped with an overflow outlet for maintaining a constant water level.

Oven


Procedure:

Step 1: Dry the specimen to a constant mass at a temperature of 52 ± 3°C (125 ± 5°F). Recently compacted laboratory samples, which have not been exposed to moisture, do not require drying.

Step 2: Cool the specimen to room temperature at 25 ± 5°C (77 ± 9°F), and record the dry mass as A.

Step 3: Immerse each specimen in the water bath at 25 ± 1°C (77 ± 1.8°F) for 4 ± 1 min, and record the immersed mass as C.

Step 4: Remove each specimen from the water bath; damp-dry the specimen by blotting it with a damp towel, and determine the surface-dry mass as B as quickly as possible (the entire operation is not to exceed 15 secs). Please note that any water that seeps from the specimen during the weighing operation is considered part of the saturated specimen.


Apparatus:

Weigh Device - conforming to AASHTO M 231, readable to 0.1 percent of the sample mass or better, and equipped with a suitable suspension apparatus.

Water Bath - For immersing the specimen in water while suspended under the weighing device, equipped with an overflow outlet for maintaining a constant water level.

Thermometer - ASTM 17C (17F), having a range of 19 to 27°C (66 to 80°F), graduated in 0.1°C (0.2°F) subdivisions.

Volumeter - having a tapered lid with a capillary bore, calibrated to 1200 mL, or an appropriate capacity depending on the size of the test sample.

Oven of appropriate size capable of maintaining a uniform temperature of 110 ± 5°C (230 ± 9°F).


Procedure:

Step 1: Dry the specimen to a constant mass at a temperature of 52 ± 3°C (125 ± 5°F). Recently compacted laboratory samples, which have not been exposed to moisture, do not require drying.

Step 2: Cool the specimen to room temperature at 25 ± 5°C (77 ± 9°F), and record the dry mass as A.

Step 3: Immerse each specimen in the water bath at 25 ± 1°C (77 ± 1.8°F) and let it saturate for at least 10 min. At the end of the 10-min period, fill a calibrated volumeter with distilled water at 25 ± 1°C (77 ± 1.8°F), and weigh the volumeter. Designate this mass as D.

Step 4: Remove the saturated specimen from the water bath and damp-dry the specimen by blotting with a damp towel as quickly as possible (not to exceed 5 s). Weigh the specimen, and record the surface-dry mass as B. Any water that seeps from the specimen during the weighing operation is considered part of the saturated specimen.

Step 5: Place the specimen into the volumeter, and let it stand for at least 60 s. Bring the temperature of the water to 25 ± 1°C (77 ± 1.8°F), and cover the volumeter, making certain that some water escapes through the capillary bore of the tapered lid. Wipe the outside of the volumeter dry with a dry, absorbent cloth, and weigh the volumeter and its contents. Record this weight as E.


Procedure:

This procedure can be used for testing specimens that are not required to be saved and that contain a substantial amount of moisture. Specimens obtained by coring or sawing can be tested the same day by this method.
The testing procedure is the same as in Method A or B except for the sequence of operations. The dry mass A of the specimen is determined last.
If Method A is followed for the Rapid Test;
Step 1: Immerse each specimen in the water bath at 25 ± 1°C (77 ± 1.8°F) for 4 ± 1 min, and record the immersed mass as C.

Step 2: Remove each specimen from the water bath; damp-dry the specimen by blotting it with a damp towel, and determine the surface-dry mass as B as quickly as possible (the entire operation is not to exceed 15 s). Any water that seeps from the specimen during the weighing operation is considered part of the saturated specimen.

Step 3: Place the specimen in a large, flat-bottom drying pan of known mass in an oven at 110 ± 5°C (230 ± 9°F). The specimen shall continue in oven until it can be easily separated to the point where the particles of the fine aggregate-asphalt portion are not larger than 6.3 mm (1/4 in.). Place the separated specimen in an oven at 110 ± 5°C (230 ± 9°F), and dry to a constant mass. Cool the pan and specimen to room temperature at 25 ± 5°C (77 ± 9°F). Determine the mass of the pan and specimen, subtract the mass of the pan, and record as the dry mass, A.


If Method B is followed for the Rapid Test;

Step 1: Immerse each specimen in the water bath at 25 ± 1°C (77 ± 1.8°F)and let it saturate for at least 10 min. At the end of the 10-min period, fill a calibrated volumeter with distilled water at 25 ± 1°C (77 ± 1.8°F), and weigh the volumeter. Designate this mass as D.

Step 2: Remove the saturated specimen from the water bath and damp-dry the specimen by blotting with a damp towel as quickly as possible (not to exceed 5 s). Weigh the specimen, and record the surface-dry mass as B. Any water that seeps from the specimen during the weighing operation is considered part of the saturated specimen.

Step 3: Place the specimen into the volumeter, and let it stand for at least 60 s. Bring the temperature of the water to 25 ± 1°C (77 ± 1.8°F), and cover the volumeter, making certain that some water escapes through the capillary bore of the tapered lid. Wipe the outside of the volumeter dry with a dry, absorbent cloth, and weigh the volumeter and its contents. Record this weight as E.

Step 4: Place the specimen in a large, flat-bottom drying pan of known mass in an oven at 110 ± 5°C (230 ± 9°F). The specimen shall continue in oven until it can be easily separated to the point where the particles of the fine aggregate-asphalt portion are not larger than 6.3 mm (1/4 in.). Place the separated specimen in an oven at 110 ± 5°C (230 ± 9°F), and dry to a constant mass. Cool the pan and specimen to room temperature at 25 ± 5°C (77 ± 9°F). Determine the mass of the pan and specimen, subtract the mass of the pan, and record as the dry mass, A.


Calculation - Method A:

Calculate the bulk specific gravity (Gmb) of the specimen as follows;

Bulk Sp . Gravity =  A B C

Calculate the percent of water absorbed by the specimen (on a volume basis) as follows;

Perc . Water Absorbed by Vol =  ( B A B C ) × 100 where:
A = mass of the specimen in air, g;
B = mass of the surface-dry specimen in air, g; and
C = mass of the specimen in water, g


Calculation - Method B:

Calculate the bulk specific gravity (Gmb) of the specimen as follows;

Bulk Sp . Gravity =  A B + D E

Calculate the percent of water absorbed by the specimen (on a volume basis) as follows;

Perc . Water Absorbed by Vol =  ( B A B + D E ) × 100 where:
A = mass of dry specimen, g;
B = mass of the surface-dry specimen, g; and
D = mass of the volumeter filled with water at 25 ± 1°C (77 ± 1.8°F), g; and
E = mass of the volumeter filled with the specimen and water at 25 ± 1°C (77 ± 1.8°F), g.


For Method C (Rapid Test) any of the above formulas can be adopted as applicable.

BULK SPECIFIC GRAVITY AND ABSORPTION - METHOD A




Output:

Bulk Specific Gravity:

Percent of water absorbed by the specimen (on a volume basis):

Report Section - Method A

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