Standard Method of Test for

Determination of Draindown
Characteristics in Uncompacted
Asphalt Mixtures

AASHTO Designation: T 305-14

American Association of State Highway and Transportation Officials

444 North Capitol Street N.W., Suite 249
Washington, D.C. 20001

© 2015 by the American Association of State Highway and Transportation Officials.

All rights reserved. Duplication is a violation of applicable law.
Standard Method of Test for

Determination of Draindown Characteristics

in Uncompacted Asphalt Mixtures

AASHTO Designation: T 305-14

1. SCOPE
1.1. This test method covers the determination of the amount of draindown material in an uncompacted
asphalt mixture sample when the sample is held at elevated temperatures comparable to those
encountered during the production, storage, transport, and placement of the mixture. The test is
particularly applicable to mixtures such as porous asphalt (open-graded friction course) and Stone
Matrix Asphalt (SMA).

1.2. The values stated in SI units are to be regarded as the standard.

1.3. This standard may involve hazardous materials, operations, and equipment. This standard does
not purport to address all of the safety concerns 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 DOCUMENTS
2.1. AASHTO Standards:
 M 92, Wire-Cloth Sieves for Testing Purposes
 R 47, Reducing Samples of Hot Mix Asphalt (HMA) to Testing Size
 T 245, Resistance to Plastic Flow of Asphalt Mixtures Using Marshall Apparatus
 T 255, Total Evaporable Moisture Content of Aggregate by Drying

3. TERMINOLOGY
3.1. Definitions:

3.1.1. draindown material—For the purpose of this test method, draindown material is considered to be
that portion of material that separates itself from the sample as a whole and is deposited outside
the wire basket during the test. The draindown material may be composed of either asphalt binder
or a combination of asphalt binder and fine aggregate.

3.1.2. draindown—The process by which draindown material separates itself from the sample as a
whole.

4. SUMMARY OF METHOD
4.1. A sample of the asphalt mixture to be tested is prepared in the laboratory or obtained from field
production. The sample is placed in a wire basket, which is positioned on a plate or other suitable
container of known mass. The sample, basket, and plate or container are placed in a forced-draft

TS-2c T 305-1 AASHTO

© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
 oven for 1 h at a preselected temperature. At the end of 1 h, the basket containing the sample is
removed from the oven, along with the plate or container and the mass of the plate or container is
determined. The amount of draindown material is then calculated.

5. SIGNIFICANCE AND USE

5.1. This test method can be used to determine whether the amount of draindown material measured
for a given asphalt mixture is within acceptable levels. The test provides an evaluation of the
draindown potential of an asphalt mixture during mixture design or during field production. This
test is primarily used for mixtures with high coarse aggregate content such as porous asphalt
(open-graded friction course) and SMA.

6. APPARATUS
6.1. Forced-Draft Oven—Capable of maintaining the temperature in a range from 120 to 175°C
(250 to 350°F). The oven should maintain the set temperature to within ±2°C (±3.6°F).

6.2. Plates—Or other suitable containers of appropriate size. The plates or containers used should be
of appropriate durability to withstand the oven temperatures. Cake pans or pie tins are examples of
suitable types of containers.

6.3. Standard Basket—Meeting the dimensions shown in Figure 1. The basket shall be constructed
using standard 6.3-mm (0.25-in.) sieve cloth as specified in M 92.

6.4. Balance—Accurate to 0.1 g.

6.5. Other apparatus—Spatulas, trowels, bowls, and mixer as needed.

7. SAMPLE PREPARATION
7.1. Laboratory-Prepared Samples:

7.1.1. Number of Samples—For each mixture tested, the draindown characteristics should be determined
at two different temperatures. The two temperatures should be the anticipated plant production
temperature, as well as 15°C (27°F) above that temperature (Note 1). For each temperature,
duplicate samples should be tested. Thus for one asphalt mixture, a minimum of four samples will
be tested.
Note 1—When using the test as part of the mixture design procedure, the test should be
performed at two temperatures in order to determine the potential effect that plant temperature
variation may have on the mixture during production. When the test is used in the field during
production, it should be necessary to perform the test at the plant production temperature only.

7.1.2. Dry the aggregate to a constant mass in accordance with T 255, and sieve it into the appropriate
size fractions as indicated in T 245.

7.1.3. Determine the anticipated plant production temperature or select a mixing temperature in
accordance with T 245.

TS-2c T 305-2 AASHTO

© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
7.1.4. Place into separate pans for each test sample the amount of each size fraction required to produce
completed mixture samples having a mass of 1200 ± 200 g. The aggregate fractions shall be
combined such that the resulting aggregate blend has the same gradation as the job mix formula.
Place the aggregate samples in an oven and heat them to a temperature not to exceed the mixing
temperature established in Section 7.1.3 by more than approximately 28°C (50°F).

7.1.5. Heat the asphalt binder to the temperature established in Section 7.1.3.

Figure 1—Wire Basket Assembly

TS-2c T 305-3 AASHTO

© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
7.1.6. Place the heated aggregate in the mixing bowl. Add any stabilizers (Note 2) and thoroughly mix
the dry components. Form a crater in the aggregate blend and add the required amount of asphalt
binder. The amount of asphalt binder shall be such that the final sample has the same asphalt
content as the job mix formula. At this point, the temperature of the aggregate and asphalt binder
shall be within the limits of the mixing temperature established in Section 7.1.3. Using a spatula
(if mixing by hand) or a mixer, mix the aggregate (and stabilizer, if any) and asphalt binder
quickly until the aggregate is thoroughly coated.
Note 2—Some types of stabilizers, such as fibers or some polymers, must be added directly to the
aggregate prior to mixing with the asphalt binder. Other types of stabilizers must be added directly
to the asphalt binder prior to blending with the aggregate.

7.2. Plant-Produced Samples:

7.2.1. Number of Samples—For plant-produced samples, duplicate samples should be tested at the plant
production temperature.

7.2.2. Samples may be obtained during plant production by sampling the mixture at any appropriate
location, such as the trucks prior to the mixture leaving the plant. Samples obtained during actual
production should be reduced to the proper test sample size by R 47.
Note 3—Caution should be exercised when sampling from surge or storage bins because
draindown may already have taken place.

8. PROCEDURE
8.1. Transfer the hot laboratory-produced or plant-produced uncompacted mixture sample to a tared
wire basket as described in Section 6.3. Place the entire sample in the wire basket. Do not
consolidate or otherwise disturb the sample after transferring it to the basket. Determine the mass
of the sample to the nearest 0.1 g. Care should be exercised to ensure that the sample does not cool
more than 25°C (77°F) below the test temperature. (See Section 8.2.)

8.2. Determine and record the mass of a plate or other suitable container to the nearest 0.1 g. Place the
basket on the plate or container and place the assembly into the oven at the temperature as
determined in Section 7.1.1 or 7.2.1 for 60 ± 5 min. If the sample has cooled more than 25°C
(77°F) below the test temperature, the test should be conducted for 70 ± 5 min.

8.3. After the sample has been in the oven for the time specified in Section 8.2, remove the basket and
plate or container from the oven. Determine and record the mass of the plate or container plus
draindown material to the nearest 0.1 g.

9. CALCULATIONS
9.1. Calculate the percent of mixture that drained by subtracting the initial plate or container mass from
the final plate or container mass and dividing this value by the initial total sample mass. Multiply
the result by 100 to obtain a percentage.
M f − Mi
× 100 =
percent of mixture that drained or percent draindown
Mt

TS-2c T 305-4 AASHTO

© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.
 where:
Mf = final plate or container mass;
Mi = initial plate or container mass; and
Mt = initial total sample mass.

10. REPORT
10.1. Report the average percent draindown (average percent of mixture that drained) at each of the test
temperatures.

TS-2c T 305-5 AASHTO

© 2015 by the American Association of State Highway and Transportation Officials.
All rights reserved. Duplication is a violation of applicable law.