Standard Method of Test for

Moisture-Density Relations of Soils

Using a 2.5-kg (5.5-lb) Rammer and
a 305-mm (12-in.) Drop

AASHTO Designation: T 99-10

American Association of State Highway and Transportation Officials

444 North Capitol Street N.W., Suite 249
Washington, D.C. 20001
Standard Method of Test for

Moisture-Density Relations of Soils

Using a 2.5-kg (5.5-lb) Rammer and a
305-mm (12-in.) Drop

AASHTO Designation: T 99-10

1. SCOPE
1.1. These methods of test are intended for determining the relation between the moisture content and
density of soils compacted in a mold of a given size with a 2.5-kg (5.5-lb) rammer dropped from a
height of 305 mm (12 in.). Four alternate procedures are provided as follows:
 Method A—A 101.60-mm (4-in.) mold: Soil material passing a 4.75-mm (No. 4) sieve
Sections 4 and 5.
 Method B—A 152.40-mm (6-in.) mold: Soil material passing a 4.75-mm (No. 4) sieve
Sections 6 and 7.
 Method C—A 101.60-mm (4-in.) mold: Soil material passing a 19.0-mm (3/4-in.) sieve
Sections 8 and 9.
 Method D—A 152.40-mm (6-in.) mold: Soil material passing a 19.0-mm (3/4-in.) sieve
Sections 10 and 11.

1.2. The method to be used should be indicated in the specifications for the material being tested. If no
method is specified, the provisions of Method A shall govern.

1.3. This test method applies to soil mixtures that have 40 percent or less retained on the 4.75-mm
(No. 4) sieve, when Method A or B is used and 30 percent or less retained on the 19.0-mm (3/4-in.)
sieve, when Method C or D is used. The material retained on these sieves shall be defined as
oversized particles (coarse particles).

1.4. If the test specimen contains oversize particles, and the test specimen is used for field density
compaction control, corrections must be made according to T 224 to compare the total field
density with the compacted specimen density. The person or agency specifying this method shall
specify a minimum percentage of oversize particles below which correction for oversize need not
be applied. If no minimum percentage is specified, correction shall be applied to samples with
more than 5 percent by mass of oversize particles.

1.5. If the specified oversized maximum tolerances are exceeded, other methods of compaction control
must be used.
Note 1—One method for the design and control of the compaction of such soils is to use a test fill
to determine the required degree of compaction and a method to obtain that compaction. Then use
a method specification to control the compaction by specifying the type and size of compaction
equipment, the lift thickness, and the number of passes.

1.6. The following applies to all specified limits in this standard: For the purposes of determining
conformance with these specifications, an observed value or a calculated value shall be rounded
off “to the nearest unit” in the last right-hand place of figures used in expressing the limiting
value, in accordance with ASTM E 29.

TS-1b T 99-1 AASHTO

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

2. REFERENCED DOCUMENTS
2.1. AASHTO Standards:
 M 92, Wire-Cloth Sieves for Testing Purposes
 M 231, Weighing Devices Used in the Testing of Materials
 T 19M/T 19, Bulk Density (“Unit Weight”) and Voids in Aggregate
 T 224, Correction for Coarse Particles in the Soil Compaction Test
 T 265, Laboratory Determination of Moisture Content of Soils

2.2. ASTM Standards:

 D 2168, Standard Practices for Calibration of Laboratory Mechanical-Rammer Soil
Compactors
 E 29, Standard Practice for Using Significant Digits in Test Data to Determine Conformance
with Specifications

3. APPARATUS
3.1. Molds—The molds shall be solid-wall, metal cylinders manufactured with dimensions and
capacities shown in Sections 3.1.1, 3.1.2, and Figures 1 and 2. They shall have a detachable collar
assembly approximately 60 mm (2.375 in.) in height, to permit preparation of compacted
specimens of soil-water mixtures of the desired height and volume. The mold and collar assembly
shall be so constructed that it can be fastened firmly to a detachable base plate made of the same
material (Note 2). The base plate shall be plane to 0.005 in. as shown in Figures 1 and 2.
Note 2—Alternate types of molds with capacities as stipulated herein may be used, provided the
test results are correlated with those of the solid-wall mold on several soil types and the same
moisture-density results are obtained. Records of such correlation shall be maintained and readily
available for inspection, when alternate types of molds are used.

3.1.1. A 101.6-mm (4-in.) mold having a capacity of 0.000943 ± 0.000008 m3 (1/30 (0.0333) ± 0.0003 ft3)
with an internal diameter of 101.60 ± 0.41 mm (4.000 ± 0.016 in.) and a height of 116.43 ±
0.13 mm (4.584 ± 0.005 in.) (Figure 1).

3.1.2. A 152.4-mm (6-in.) mold having a capacity of 0.002124 ± 0.000021 m3 (1/13.33 (0.07500) ±
0.00075 ft3) with an internal diameter of 152.40 ± 0.66 mm (6.000 ± 0.026 in.) and a height of
116.43 ± 0.13 mm (4.584 ± 0.005 in.) (Figure 2).

3.1.3. Molds Out of Tolerance Due to Use—A mold that fails to meet manufacturing tolerances after
continued service may remain in use provided those tolerances are not exceeded by more than
50 percent; and the volume of the mold, calibrated in accordance with T 19M/T 19 for Unit Mass
of Aggregate, is used in the calculations.

TS-1b T 99-2 AASHTO

Notes: 1. All dimensions shown in millimeters unless otherwise noted.
2. Hanger on the mold portion only cannot extend above the midheight line.
3. Figure 1 is to be used for all compaction molds purchased after the publication of the 21st edition (HM-21).

Figure 1—Cylindrical Mold and Base Plate (101.6-mm Mold)

TS-1b T 99-3 AASHTO

Notes: 1. All dimensions shown in millimeters unless otherwise noted.
2. Hanger on the mold portion only cannot extend above the midheight line.
3. Figure 2 is to be used for all compaction molds purchased after the publication of the 21st edition (HM-21).

Figure 2—Cylindrical Mold and Base Plate (152.4-mm Mold)

TS-1b T 99-4 AASHTO

Table 1—Dimensional Equivalents for Figure 1
mm in. mm in.
3.18 ± 0.64 0.125 ± 0.025 50.80 ± 0.64 2.000 ± 0.025
3.81 0.150 60.33 ± 1.27 2.375 ± 0.050
6.35 ± 1.27 0.250 ± 0.050 101.60 ± 0.41 4.000 ± 0.016
7.62 0.300 107.95 ± 1.27 4.250 ± 0.050
9.53 ± 0.64 0.375 ± 0.025 114.30 ± 2.54 4.500 ± 0.100
12.70 ± 2.54 0.500 ± 0.100 116.43 ± 0.13 4.584 ± 0.005
17.78 ± 1.27 0.700 ± 0.050 152.40 ± 2.54 6.000 ± 0.100
20.32 0.800 165.10 ± 2.54 6.500 ± 0.100
38.10 ± 2.54 1.500 ± 0.100 172.72 ± 2.54 6.800 ± 0.100
0.000943 ± 0.000008 m3 1/30 ± 0.0003 ft3

Table 2—Dimensional Equivalents for Figure 2

mm in. mm in.
3.18 ± 0.64 0.125 ± 0.025 50.80 ± 0.64 2.000 ± 0.025
3.81 0.150 60.33 ± 1.27 2.375 ± 0.050
6.35 ± 1.27 0.250 ± 0.050 116.43 ± 0.13 4.584 ± 0.005
7.62 0.300 152.40 ± 0.66 6.000 ± 0.026
9.53 ± 0.64 0.375 ± 0.025 158.75 ± 1.27 6.250 ± 0.050
12.70 ± 2.54 0.500 ± 0.100 165.10 ± 2.54 6.500 ± 0.100
17.78 ± 1.27 0.700 ± 0.050 172.72 ± 2.54 6.800 ± 0.100
20.32 0.800 203.23 ± 2.54 8.000 ± 0.100
38.10 ± 2.54 1.500 ± 0.100 215.90 ± 2.54 8.500 ± 0.100
0.002124 ± 0.000021 m3 1/13.33 ± 0.00075 ft3

3.2. Rammer:

3.2.1. Manually Operated—Metal rammer with a mass of 2.495 ± 0.009 kg (5.5 ± 0.02 lb), and having a
flat circular face of 50.80-mm (2.000-in.) diameter with a manufacturing tolerance of ± 0.25 mm
(0.01 in.). The in-service diameter of the flat circular face shall be not less than 50.42 mm
(1.985 in.). The rammer shall be equipped with a suitable guide sleeve to control the height of
drop to a free fall of 305 ± 2 mm (12.00 ± 0.06 in.) above the elevation of the soil. The guide
sleeve shall have at least four vent holes, no smaller than 9.5-mm (3/8-in.) diameter spaced
approximately 90 degrees (1.57 rad) apart and approximately 19 mm (3/4 in.) from each end; and
shall provide sufficient clearance so the free fall of the rammer shaft and head is unrestricted.

3.2.2. Mechanically Operated—A metal rammer that is equipped with a device to control the height of
drop to a free fall of 305 ± 2 mm (12.00 ± 0.06 in.) above the elevation of the soil and uniformly
distributes such drops to the soil surface (Note 3). The rammer shall have a mass of 2.495 ±
0.009 kg (5.5 ± 0.02 lb), and have a flat circular face of 50.80-mm (2.000-in.) diameter with a
manufactured tolerance of ± 0.25 mm (0.01 in.). The in-service diameter of the flat circular face
shall be not less than 50.42 mm (1.985 in.). The mechanical rammer shall be calibrated by
ASTM D 2168.
Note 3—It may be impractical to adjust the mechanical apparatus so the free fall is 305 mm
(12 in.) each time the rammer is dropped, as with the manually operated rammer. To make the
adjustment of free fall, the portion of loose soil to receive the initial blow should be slightly
compressed with the rammer to establish the point of impact from which the 305-mm drop is
determined. Subsequent blows on the layer of soil being compacted may all be applied by
dropping the rammer from a height of 305 mm above the initial-setting elevation; or, when the
mechanical apparatus is designed with a height adjustment for each blow, all subsequent blows
should have a rammer free fall of 305 mm measured from the elevation of the soil as compacted
by the previous blow. A more detailed calibration procedure for laboratory mechanical-rammer
soil compactors can be found in ASTM D 2168.

TS-1b T 99-5 AASHTO

3.2.3. Rammer Face—The circular face rammer shall be used, but a sector face may be used as an
alternative, provided the report shall indicate type of face used other than the 50.8-mm (2-in.)
circular face, and it shall have an area equal to that of the circular face rammer.

3.3. Sample Extruder (for Solid-Walled Molds Only)—A jack, lever, frame, or other device adopted for
the purpose of extruding compacted specimens from the mold.

3.4. Balances and Scales—A balance or scale conforming to the requirements of M 231, Class G 20.
Also, a balance conforming to the requirements of M 231, Class G 2.
Note 4—The capacity of the metric balance or scale should be approximately 11.5 kg when used
to weigh the 152.40-mm (6-in.) mold and compacted, moist soil; however, when the 101.60-mm
(4-in.) mold is used, a balance or scale of lesser capacity than the 11.5 kg may be used, if the
sensitivity and readability are 5 g.

3.5. Drying Oven—A thermostatically controlled drying oven capable of maintaining a temperature of
110 ± 5°C (230 ± 9°F) for drying moisture samples.

3.6. Straightedge—A hardened-steel straightedge at least 250 mm (10 in.) in length. It shall have one
beveled edge, and at least one longitudinal surface (used for final trimming) shall be plane within
0.250 mm per 250 mm (0.01 in. per 10 in.) (0.1 percent) of length within the portion used for
trimming the soil (Note 5).
Note 5—The beveled edge may be used for final trimming if the edge is true within a tolerance of
0.250 mm per 250 mm (0.1 percent) of length; however, with continued use, the cutting edge may
become excessively worn and not suitable for trimming the soil to the level of the mold. The
straightedge should not be so flexible that trimming the soil with the cutting edge will cause a
concave soil surface.

3.7. Sieves—50-mm (2-in.), 19.0-mm (3/4-in.), and 4.75-mm (No. 4) sieves conforming to the
requirements of M 92.

3.8. Mixing Tools—Miscellaneous tools such as mixing pan, spoon, trowel, spatula, etc., or a suitable
mechanical device for thoroughly mixing the sample of soil with increments of water.

3.9. Containers—Suitable containers made of material resistant to corrosion and not subject to change
in mass or disintegration on repeated heating and cooling. Containers shall have close-fitting lids
to prevent loss of moisture from samples before initial mass determination and to prevent
absorption of moisture from the atmosphere following drying and before final mass determination.
One container is needed for each moisture content determination.

METHOD A

4. SAMPLE
4.1. If the soil sample is damp when received from the field, dry it until it becomes friable under a
trowel. Drying may be in air or by use of a drying apparatus that is maintained at a temperature not
exceeding 60°C (140°F). Then thoroughly break up the aggregations in such a manner as to avoid
reducing the natural size of individual particles.

4.2. Sieve an adequate quantity of the representative pulverized soil over the 4.75-mm (No. 4) sieve.
Discard the coarse material, if any, retained on the 4.75-mm (No. 4) sieve.

4.3. Select a representative sample, with a mass of approximately 3 kg (7 lb) or more, of the soil
prepared as described in Sections 4.1 and 4.2.

TS-1b T 99-6 AASHTO

 Note 6—When developing a compaction curve for free-draining soils, such as uniform sands and
gravels, where seepage occurs at the bottom of the mold and base plate, taking a representative
moisture content sample from the mixing bowl may be preferred to determine the amount of
moisture available for compaction.

5. PROCEDURE
5.1. Thoroughly mix the selected representative sample with sufficient water to dampen it to
approximately four percentage points below optimum moisture content.

5.2. Form a specimen by compacting the prepared soil in the 101.60-mm (4-in.) mold (with collar
attached) in three approximately equal layers to give a total compacted depth of about 125 mm
(5 in.). Prior to compaction, place the loose soil into the mold and spread into a layer of uniform
thickness. Lightly tamp the soil prior to compaction until it is not in a loose or fluffy state, using
either the manual compaction rammer or a similar device having a face diameter of approximately
50 mm (2 in.). Following compaction of each of the first two layers, any soil adjacent to the mold
walls that has not been compacted or extends above the compacted surface shall be trimmed using
a knife or other suitable device and evenly distributed on top of the layer. Compact each layer by
25 uniformly distributed blows from the rammer dropping free from a height of 305 mm (12 in.)
above the elevation of the soil when a sleeve-type rammer is used, or from 305 mm above the
approximate elevation of compacted soil when a stationary mounted type of rammer is used.
During compaction, the mold shall rest firmly on a dense, uniform, rigid, and stable foundation
or base. This base shall remain stationary during the compaction process (Note 7).
Note 7—Each of the following has been found to be a satisfactory base on which to rest the mold
during compaction of the soil: a block of concrete, with a mass not less than 90 kg (200 lb),
supported by a relatively stable foundation; a sound concrete floor; and for field application, such
surfaces as are found in concrete box culverts, bridges, and pavements.

5.2.1. Following compaction, remove the extension collar, carefully trim the compacted soil even with
the top of the mold by means of the straightedge, and determine the mass of the mold and moist
soil in kilograms to the nearest 5 g, or determine the mass in pounds to the nearest 0.01 pounds.
Calculate the wet density, W1, as described in Section 12.2 or 12.3.

5.3. Remove the material from the mold and slice vertically through the center. Take a representative
sample of the material from one of the cut faces (Figure 3) and weigh immediately. Determine the
moisture content in accordance with T 265 and record the results.

TS-1b T 99-7 AASHTO

Shaded region
illustrates a
representative
moisture content
sample
Cut face

Figure 3—Representative Moisture Content Sample Selection

5.4. Thoroughly break up the remaining portion of the molded specimen until it will pass through a
4.75-mm (No. 4) sieve as judged by eye, and add to the remaining portion of the sample being
tested. Add water in sufficient amount to increase the moisture content of the soil 1 to 2
percentage points (water content increments should not exceed 2.5 percent except when heavy
clay soils or organic soils exhibiting flat elongated curves are encountered; the water content
increments may be increased to a maximum of 4 percent) and repeat the above procedure for each
increment of water added. Continue this series of determinations until there is either a decrease or
no change in the wet unit mass, W1, per cubic meter (cubic foot) of the compacted soil (Note 8).
Note 8—In instances where the soil material is fragile in character and will reduce significantly in
grain size due to repeated compaction, and in cases where the soil is a heavy-textured clayey
material into which it is difficult to incorporate water, a separate and new sample shall be used in
each compaction test. In these cases, separate samples shall be thoroughly mixed with amounts of
water sufficient to cause the moisture contents of the samples to vary by approximately two
percentage points. The moisture points selected shall bracket the optimum moisture content, thus
providing samples that, when compacted, will increase in mass to the maximum density and then
decrease in mass. The samples of soil-water mixtures shall be placed in covered containers and
allowed to stand for not less than 12 h before making the moisture-density test.

5.4.1. In instances where the soil material is fragile in character and will be reduced significantly in grain
size by repeated compaction, a separate and new sample shall be used in each compaction test.

METHOD B

6. SAMPLE
6.1. Select the representative sample in accordance with Section 4.3, except that it shall have a mass of
approximately 7 kg (16 lb).

TS-1b T 99-8 AASHTO

7. PROCEDURE
7.1. Follow the same procedure as described for Method A in Section 5, except for the following:
Form a specimen by compacting the prepared soil in the 152.4-mm (6-in.) mold (with collar
attached) in three approximately equal layers to give a total compacted depth of about 125 mm
(5 in.), each layer being compacted by 56 uniformly distributed blows from the rammer. Calculate
the wet density, W1, as described in Section 12.2 or 12.3.

METHOD C

8. SAMPLE
8.1. If the soil sample is damp when received from the field, dry it until it becomes friable under a
trowel. Drying may be in air or by use of a drying apparatus that is maintained at a temperature not
exceeding 60°C (140°F). Then thoroughly break up the aggregations in such a manner as to avoid
reducing the natural size of individual particles.

8.2. Sieve an adequate quantity of the representative pulverized soil over the 19.0-mm sieve. Discard
the coarse material, if any, retained on the 19.0-mm sieve (Note 9).
Note 9—The discarded coarse material may be utilized in T 224.

8.3. Select a representative sample, having a mass of approximately 5 kg (11 lb) or more, of the soil
prepared as described in Sections 8.1 and 8.2.

9. PROCEDURE
9.1. Thoroughly mix the selected representative sample with sufficient water to dampen it to
approximately four percentage points below optimum moisture content.

9.2. Form a specimen by compacting the prepared soil in the 101.60-mm (4-in.) mold (with collar
attached) in three approximately equal layers to give a total compacted depth of about 125 mm
(5 in.). Prior to compaction, place the loose soil into the mold and spread into a layer of uniform
thickness. Lightly tamp the soil prior to compaction until it is not in a loose or fluffy state, using
either the manual compaction rammer or a similar device having a face diameter of approximately
50 mm (2 in.). Following compaction of each of the first two layers, any soil adjacent to the mold
walls that has not been compacted or extends above the compacted surface shall be trimmed
using a knife or other suitable device and evenly distributed on top of the layer. Compact
each layer by 25 uniformly distributed blows from the rammer dropping free from a height of
305 mm (12 in.) above the elevation of the soil when a sleeve-type rammer is used, or from
305 mm (12 in.) above the approximate elevation of each finely compacted layer when a
stationary mounted-type rammer is used. During compaction, the mold shall rest firmly on a
dense, uniform, rigid, and stable foundation (Note 7).

9.2.1. Following compaction, remove the extension collar, carefully trim the compacted soil even with
the top of the mold by means of the straightedge. Holes developed in the surface by removal of
coarse material shall be patched with smaller-sized material. Determine the mass of the mold and
moist soil in kilograms to the nearest 5 g, or determine the mass in pounds to the nearest 0.01 lb.
Calculate the wet density, W1, as described in Section 12.2 or 12.3.

9.3. Remove the material from the mold and slice vertically through the center. Take a representative
sample of the material from one of the cut faces and weigh immediately. Determine the moisture
content in accordance with T 265 and record the results.

TS-1b T 99-9 AASHTO

9.4. Thoroughly break up the remainder of the material until it will pass through a 19.0-mm sieve and
90 percent of the soil aggregations will pass a 4.75-mm sieve as judged by eye, and add to the
remaining portion of the sample being tested. Add water in sufficient amounts to increase the
moisture content of the soil sample by 1 or 2 percentage points, and repeat the above procedure for
each increment of water added. Continue this series of determinations until there is either a
decrease or no change in the wet mass, W1, per cubic meter (cubic foot) of compacted soil
(Note 8).

METHOD D

10. SAMPLE
10.1. Select the representative sample in accordance with Section 8.3 except that it shall have a mass of
approximately 11 kg (25 lb).

11. PROCEDURE
11.1. Follow the same procedure as described for Method C in Section 9, except for the following: Form
a specimen by compacting the prepared soil in the 152.4-mm (6-in.) mold (with collar attached) in
three approximately equal layers to give a total compacted depth of about 125 mm (5 in.), each
layer being compacted by 56 uniformly distributed blows from the rammer. Calculate the wet
density, W1, as described in Section 12.2 or 12.3.

CALCULATIONS AND REPORT

12. CALCULATIONS
12.1. The mold factor can be related to the volume of the mold as follows:
F = 1/V (1)
where:
F = mold factor; and
V = volume of mold.

12.2. The wet density can be determined using the mold factor. For masses recorded in kilograms, the
unit of wet density is kilograms per cubic meter of compacted soil. For masses recorded in
pounds, the unit of wet density is pounds per cubic foot of compacted soil.
W1 = ( A – B ) × F (2)
where:
A = mass of compacted specimen and mold;
B = mass of mold;
F = mold factor as given in Table 3; and
W1 = wet density.

TS-1b T 99-10 AASHTO

Table 3—Mold Factors for Molds in Compliance with Sections 3.1.1 or 3.1.2
Mold Factor
Method For Masses Recorded in Kilograms For Masses Recorded in Pounds
A 1060 30
B 471 13.3
C 1060 30
D 471 13.3
For used molds in compliance with Section 3.1.3, determine the mold factor in accordance with Section 3.1.3 and Equation 1.

12.3. Alternatively, the wet density can be determined using the mold volume. For masses recorded in
kilograms, the unit of wet density is kilograms per cubic meter of compacted soil. For masses
recorded in pounds, the unit of wet density is pounds per cubic foot of compacted soil.
W1 = ( A – B )/V (3)
where:
V = mold volume as given in Section 3.1.1 for Methods A and C, or Section 3.1.2 for
Methods B and D. For used molds in compliance with Section 3.1.3, determine the mold
volume in accordance with Section 3.1.3.

12.4. The dry density is related to the wet density as follows:

W1
W = × 100 (4)
w + 100
where:
w = moisture content (percent) of the specimen, as determined by T 265; and
W = dry density, in kilograms per cubic meter of compacted soil, or pounds per cubic foot of
compacted soil.

13. MOISTURE-DENSITY RELATIONSHIP

13.1. The calculations in Section 12 shall be made to determine the wet density (unit mass) and oven-
dry density (unit mass) in kilograms per cubic meter or pounds per cubic foot of the compacted
samples. The oven-dry densities of the soil shall be plotted as ordinates, and the corresponding
moisture content as abscissas.

13.2. Optimum Moisture Content—When the densities and corresponding moisture contents for the soil
have been determined and plotted as indicated in Section 13.1, it will be found that by connecting
the plotted points with a smooth line, a curve is produced. The moisture content corresponding to
the peak of the curve shall be termed the “optimum moisture content” of the soil under the
above compaction.

13.3. Maximum Density—The oven-dry density in kilograms per cubic meter or pounds per cubic
foot of the soil at optimum moisture content shall be termed “maximum density” under the
above compaction.

14. REPORT
14.1. The report shall include the following:

14.1.1. The method used (Method A, B, C, or D).

14.1.2. The optimum moisture content, as a percentage, to the nearest whole number.

TS-1b T 99-11 AASHTO

14.1.3. The maximum density in kilograms per cubic meter to the nearest 10 kg/m3 or in pounds per cubic
foot, to the nearest whole number.

14.1.4. Type of face if other than 50.8 mm (2 in.) circular.

15. PRECISION STATEMENT

15.1. Repeatability (Single Operator)—Two results obtained by the same operation on the same sample
in the same laboratory using the same apparatus and on different days should be considered
suspect if they differ by more than 10 percent of their mean for optimum moisture content and
35 kg/m3 (2.2 lb/ft3) for maximum density.

15.2. Reproducibility (Multilaboratory)—Two results obtained by different operators in different

laboratories should be considered suspect if they differ by more than 15 percent of their mean for
optimum moisture and 72 kg/m3 (4.5 lb/ft3) for maximum density.

TS-1b T 99-12 AASHTO