September 1, 2000
Florida Method of Test
for
LIMEROCK BEARING RATIO
Designation: FM 5-515
1.
SCOPE
This test method is intended for the determination of the bearing value of soils when they
are compacted in the laboratory at moistures varying from the dry to wet side of optimum
using a 4.54 kg (10-pound) rammer dropped from a height of 457 mm (18 inches). The
test is useful for evaluating limerock and other soils used for base, stabilized subgrade, and
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subgrade or embankment material encountered in Florida.
2.
APPARATUS
2.1
Molds - The molds shall be cylindrical in shape, made of metal, with an
internal diameter of 152.40 ± 0.51 mm (6.00 ± 0.02 inches) and a height of
152.40 ± 0.51 mm (6.00 ± 0.02 inches) (See Figure 1). They shall have a
detachable collar assembly approximately 63.5 mm (2.5 inches) in height to
permit preparation of compacted specimens of soil-water mixtures of the
desired height and volume. Molds may be of the "split" type, consisting of
two half-round sections, or a section of pipe split along one element, which
can be securely locked in place to form a cylinder. The mold and collar
assembly shall be so constructed that it can be fastened firmly to a
detachable perforated base plate.
2.1.1 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 par. 4 (Calibration of Measure) of
AASHTO T 19, Test for Unit Weight of Aggregate, is used in the calculations.
2.2
Spacer Disc - A metal disc 150.8 ± 0.8 mm (5-15/16 ± 1/32 inches) in
diameter and 35.80 ± 0.51 mm (1.41 ± 0.02 inches) in height (Figure 2) is
inserted as a false bottom in the cylinder mold during compaction. This
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This compaction procedure is a modification of AASHTO T 180-74,
Method D.
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September 1, 2000
would give a net cylinder volume of 0.002124 ±0.000021 m (1/13.33 cubic
feet).
2.3
Rammer
2.3.1 Manual Rammer - The manual rammer contact face shall have a flat circular
face with a wear tolerance of 0.25 mm (0.01 in.) and a diameter of 50.80 ±
0.13 mm (2.000 ± 0.005 inches), weighing 4.536 ± 0.009 kg (10.00 ± 0.02
pounds). The rammer shall be equipped with a suitable arrangement to
control the height of drop to a free fall of 457 ± 2 mm (18.0 ± 0.06 (1/16)
inches) above the elevation of the soil. The guide-sleeve shall have at least
4 vent holes, no smaller than 9.5 mm (3/8 in.) diameter spaced
approximately 1.57 rad (90 deg.) 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.
2.3.2 Mechanical Rammer - The rammer shall be equipped with a suitable
arrangement to control the height of drop to a free fall of 457 ± 2 mm (18.0 ±
0.06 (1/16) inches) above the elevation of the soil. The mechanical rammer
shall operate in such a manner as to provide uniform and complete coverage
of the specimen surface (8 to 10 blows per revolution of rammer). There
shall be 2.54 ± 0.76 mm (0.10 ± 0.03 in.) clearance between the rammer and
the inside surface of the mold. The specimen contact face shall be flat with a
wear tolerance of 0.25 mm (0.01 in.) and have the shape a sector of a circle
of a radius equal to 73.70 ± 0.51 mm (2.90 ± 0.02 inches) (Fig. 3). The area
of the sector face shall be 0.0020258 ± 0.0000190 m² (3.14 ± 0.03 in²). The
mechanical rammer shall be calibrated and adjusted, as necessary, in
accordance with 2.3.3. Before the initial calibration, the rammer shall weigh
4.536 ± 0.009 kg (10.00 ± 0.02 pounds).
2.3.3 Calibration and Adjustment - The mechanical rammer shall be calibrated and
adjusted as necessary, before initial use; once each year; before reuse after
anything, including repair, which may affect the test results significantly; and
whenever the test results are questionable. Each calibration and adjustment
shall be in accordance with ASTM D2168, Method A.
2.4
Surcharge Weights - One annular disc weighing 2.27 kg (5 pounds), and
additional slotted weights weighing 2.27 kg (5 pounds) (Figure 2) each are
used when surcharge is required (See Section 7.1).
2.5
Penetration Piston - The penetration piston is 49.5 mm (1.95 inches) in
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September 1, 2000
diameter and approximately 190.5 mm (7 inches) in length for a manual
loading device, or approximately 127 mm (5 inches) in length for automatic
testing machines (Figures 4, 5, 6 and 7).
2.6
Loading Device - A compression loading device capable of being operated
manually or electrically at a rate of 1.27 mm (0.05 inches) per minute can be
used to force the penetration piston into the specimen (Figures 6 and 7).
Calibration checks shall be performed when in use.
2.7
Swell Plate - A perforated base plate weighing approximately 1.13 kg (2.2
pounds), similar to that shown in Figure 3, is used.
2.8
Sample Extruder (optional) - A jack, lever, frame, or other device adapted for
the purpose of extruding compacted specimens from the mold may be
useful.
2.9
Balances - A balance or scale for weighing test samples of at least 11 kg (24
pound) capacity, sensitive and readable to 5 grams (0.01 pound), and a
balance of at least 1000-g capacity, sensitive and readable to 0.1-g is
required. Both balances shall conform to the requirements of the
Specifications for Weighing Devices Used in the Testing of Materials
(AASHTO Designation: M231). (Optional - A balance or scale of 23 kg (50
pound) or more capacity for determining percent retained on individual
sieves, sensitive and readable to 0.2%).
2.10
Drying Oven - A thermostatically controlled drying oven shall be capable of
maintaining a temperature of 110 ± 5°C (230± 9°F) for drying moisture
samples.
2.11
Straight Edge - A steel straight edge 304.8 mm (12 inches) in length. It shall
have one beveled edge, and at least one longitudinal surface (used for final
trimming) shall be plane within 0.1 percent of the length within the portion
used for trimming.
2.12
Sieves - 50 (2 inch), 19 (3/4 inch), and 4.75 mm (No. 4) sieves should
conform to the requirements of the Specifications for Sieves for Testing
Purposes (AASHTO Designation: M92).
2.13
Mixing Tools - Miscellaneous tools such as mixing pans, spoon, trowel,
spatula, etc., or a suitable mechanical device for thoroughly mixing the
sample of soil with increments of water are required.
FM 5-515
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September 1, 2000
3.
2.14
Soak Tank - A rectangular tank approximately 66 cm x 152 cm x 25 cm
(26"W x 60"L x 10"D). A smaller tank may be used if quantity of tests or
laboratory space is not large enough to accommodate the suggested size.
The tank shall have raised ridges, or other devices, in the bottom, placed in
such a manner to allow free access of water to the bottom of the mold. The
tank shall have an overflow placed so that the height of water in the tank
remains within 6.35 mm (1/4") of the same elevation as the top of the soil
sample in the mold.
2.15
Containers - Suitable containers made of material resistant to corrosion and
not subject to change in weight or disintegration on repeated heating or
cooling. One container is needed for each moisture content determination.
SAMPLE PREPARATION
3.1
If the soil is damp when received from the field, it shall be dried until it
becomes friable under the trowel. It may be dried in air or by use of drying
apparatus such that the temperature does not exceed 60°C (140°F).
3.2
Initial Preparation:
3.2.1 For materials used for base or stabilizers with particle sizes greater than 19
mm, the material shall be crushed so that the entire sample passes the 19
mm (3/4 inch) sieve by use of a mechanical jaw crusher having a minimum
jaw plate dimension of 60 x 90 mm. Those pieces not reduced by
mechanically crushing shall be manually broken up to pass the 19 mm sieve.
The material is then passed through a 4.75 mm (No. 4) sieve, the percentage
retained is recorded and the procedure is continued to Section 3.3.
3.2.2 The materials used for subgrade shall be passed through 50, 19 & 4.75 mm
(2 inch, 3/4 inch and No. 4) sieves without crushing, taking care to thoroughly
break up the aggregations in such a manner as to avoid reducing the natural
size of the individual particles. Any clay or silt aggregations shall be broken
down until they will pass through a 4.75 mm (No. 4) sieve. The percentages
retained on each sieve are then recorded. The material retained on the 50
mm (2 inch) sieve shall be discarded. The material passing the 50 mm (2
inch) sieve and retained on the 19 mm (3/4 inch) sieve shall be weighed.
This material (between the 50 and 19 mm (2 inch and 3/4 inch size)) shall be
removed from the soil and replaced with an equal weight of material passing
the 19 mm (3/4 inch) sieve and retained on the 4.75 mm (No. 4) sieve.
NOTE: If the material retained on the 4.75 mm (No. 4) sieve is seven percent or
FM 5-515
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September 1, 2000
less, the material may be added back into the sample and thoroughly mixed
with no correction.
3.3
The material shall then be separated into at least four and preferably five
portions weighing approximately 5.44 kg (12 pounds), each of which shall be
representative of the total.
3.4
Each of the separate portions shall be thoroughly mixed with amounts of
water sufficient to cause each of the moisture contents of the samples to
vary by approximately one percent with the lowest moisture content being
approximately three percentage points below the optimum moisture content.
The moisture contents selected shall bracket the optimum moisture content,
thus providing samples which, when compacted, will increase in weight to the
maximum density and then decrease in weight. The samples of soil-water
mixtures shall be placed in covered containers and allowed to stand prior to
compaction in accordance with Table 1. For the purpose of selecting a
standing time, it is not required to perform the actual classification procedure
described in AASHTO M-145 (except in the case of referee testing), if
previous data exist which provide a basis for classifying the sample.
TABLE 1
Dry Preparation Method
Soaking Times
Classification M 145
4.
Minimum Soaking Times-hours
A-3
A-2-4 ( Non-Plastic)
No Requirement
3
A-1, A-2-4 (Plastic), A-2-5, A-2-6, A-2-7,
A-4, A-5, A-6, A-7
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COMPACTION PROCEDURE
4.1
FM 5-515
Immediately prior to compacting the material, it shall be remixed and a
representative sample shall be taken for moisture content determination.
The sample shall be weighed immediately and the weight recorded. The
sample is dried in an oven at 110 ±5°C (230 ± 9°F) for at least 12 hours, or to
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September 1, 2000
constant weight to determine the moisture content. The moisture content
sample shall weigh not less than 500-g. Figure 8 shows the form used.
5.
4.2
The spacer disc shall be inserted into the bottom of the 152.4 mm (6 inch)
mold and then a specimen formed by compacting the prepared soil in the
152.4 mm (6 inch) diameter mold (with collar attached) in five equal layers to
give a total compacted depth of about 127 mm (5 inches). Each layer shall
be compacted with 56 uniformly distributed blows from the rammer, dropping
free from a height of 457 ± 2 mm (18 inches ± 1/16 inch) above the
approximate elevation of each finally compacted layer when a stationary
mounted type rammer is used. During compaction, the mold shall rest on a
uniform rigid foundation, such as is provided by a cube of concrete weighing
not less than 91 kg (200 pounds).
4.3
Following the compaction, the extension collar shall be removed, and the
compacted soil carefully trimmed even with the top of the mold by means of
the straight edge. Holes developed in the surface by removal of coarse
material shall be patched with smaller size material passing a 4.75 mm (No.
4) sieve.
4.4
A coarse filter paper (No. 4, 15 cm) shall be placed over the top surface, and
a perforated base plate clamped to the top of the mold. The mold shall be
inverted and the base plate, formerly on the bottom, removed. The spacer
disc shall be removed and a filter paper inserted. The mold and moist soil
shall then be weighed and the weight recorded on the form. Multiply the
weight of the compacted specimen and the mold less the weight of the mold,
by 470.8 (13.33) and record the result as the wet weight in kg per cubic
meter (pounds per cubic foot) of the compacted soil.
4.5
Repeat the above procedure for each increment of moisture content using
the samples prepared as described in Section 3. A minimum of four
specimens shall be compacted at varying moisture contents beginning
approximately two percentage points below the optimum moisture content
and increasing the moisture until the optimum moisture content is exceeded.
MOISTURE-DENSITY RELATIONSHIP
5.1
FM 5-515
Calculate the moisture content to the nearest 0.1 percent and the dry unit
3
3
weight of the soil to the nearest 1 kg/m (0.1 lb/ft ) as compacted for each
trial as follows:
w=
A- B
x 100
B-C
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and
Wd =
where:
Ww
x 100
w + 100
w
=
A
B
C
=
=
=
percentage of moisture in the specimen based
on oven dry mass of soil,
mass of container and wet soil,
mass of container and dry soil,
mass of container,
Wd
=
dry density in kg/m (lbs/ft3) of compacted soil, and
Ww
=
wet density in kg/m (lbs/ft3) of compacted soil.
The oven-dry unit weights in kg per cubic meter (pounds per cubic foot)
(densities) of the soil shall be plotted as ordinates and corresponding
moisture contents as abscissas (lower curve, Figure 8). Fitting the best
smooth curve through these points, a convex curve is generally obtained.
The coordinates of the peak of the curve shall be termed the optimum
moisture content and the maximum dry density of the soil, respectively.
NOTE:
6.
The data may be plotted in English units (pounds per cubic foot) and the
maximum density from the graph then converted to metric units (kg/m3) by
multiplying by the factor 16.02.
SOAKING
Following Section 4, the compacted specimens shall be placed in a soaking
tank so that the height of water remains within 6.35 mm (1/4 inch) of the
same elevation as the top of the soil sample in the mold. The soak time shall
be 48 hours ± 4 hours. A surcharge of approximately 1.13 kg (2.5 pounds)
(weight of swell plate) shall be placed on top of each sample before it is
placed in the soak tank and left in place during the entire soaking and
draining period.
6.1
FM 5-515
Draining - Before the actual penetration test is run, the specimen shall be
removed from the soaking tank and allowed to drain on a visibly level surface
for 15 ± 2 minutes. The drain surface shall be such that will allow free
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September 1, 2000
access for water to drain from the bottom of the mold. After draining, the
swell plate shall be removed and the specimen tested immediately.
7.
PENETRATION TEST
7.1
Application of Surcharge - A surcharge of 6.8 and 9.1 kg (15 and 20 pounds)
shall be applied to the stabilized subgrade and embankment specimens,
respectively. No surcharge weight is used on base materials.
7.2
Application of Load - Before any reading is taken, a seating load of 4.54 kg
(10 pounds) is applied to the specimen with the required surcharge weights
as described in Section 7.1 when using a manually operated machine as
shown in Figure 6. The deflection and load gauges are then zeroed and the
load applied through the piston at a constant rate of approximately 1.3 mm
(0.05 inches) per minute. When automatic recording equipment (Figure 7) is
used, the 4.54 kg (10 pound) seating load is not required. The recording pen
is zeroed on the chart paper before the load is applied.
Load readings shall be obtained for each 0.25 mm (0.01 inch) penetration up
to 5.08 mm (0.2 inches), after which the load reading shall be taken at 5.72,
6.35, 6.98, 7.62, 8.26, 8.89, 9.52, 10.16, 11.43, and 12.7 mm (0.225, 0.250,
0.275, 0.300, 0.325, 0.350, 0.375, 0.400, 0.450, and 0.500 inches) of
penetration. For those cases where the LBR value can obviously be
obtained very early in the penetration testing, the higher penetration readings
may be waived. Figure 9 is a suggested form sheet for recording the
necessary data obtained from a test specimen when using a manual loading
device as shown in Figure 6. Each recorded unit load, in megapascals
(pounds per square inch), shall be calculated by dividing the incremental load
by 1935 mm² (3 square inches). This unit load shall then be plotted as the
ordinate of a graph whereon the penetration, in mm (inches), is plotted as the
abscissa. A smooth curve shall be drawn through the plotted points. For
those machines which perform the test automatically but are not equipped
with recording devices, the technique is the same as for manually operated
machines.
For machines equipped with load-deflection recorders, the curve is plotted
automatically. It is well to note that most machines with attached recorders
show the load in newton (pounds) rather than in megapascals (pounds per
square inch). Since the cross-sectional area of the piston is a constant, the
load scale may easily be converted to a pressure scale simply be dividing the
load in newton (pounds) by 1935 mm (3 square inches).
FM 5-515
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September 1, 2000
8.
CALCULATIONS
8.1
Load-Penetration Relationship - The curve will usually be convex upwards
although the initial portion of the curve may be concave upwards: the
concavity is assumed to be due to surface irregularities (Figure 11). A
correction is applied by drawing a tangent to the curve at the point of
greatest slope. The corrected curve then becomes the tangent plus the
convex portion of the original curve with the origin moved to the point where
the tangent intersects the horizontal axis. Methods of correcting typical
curves are illustrated in Figures 11 and 12.
8.2
Establishing Limerock Bearing Ratio of Material - The corrected unit load
obtained at 2.54mm (0.1 inch) penetration shall be divided by 5.516 MPa
(800 psi), which is the standard strength of limerock. This ratio is then
multiplied by 100, and the resulting value is the LBR in percent.
LBR =
Corrected Unit Load
x 100
5.516
The collection of LBR values for each compacted sample should provide
sufficient data to plot an LBR vs. moisture content curve such as shown in
the upper half of Figure 8. The peak or maximum LBR value can then be
determined in the same way the maximum density is obtained from a
moisture- density curve (lower half of Figure 8). This procedure shall be
used when ever it is required to establish an LBR value for a material.
Note:
9.
(For those cases where a material is being tested to check for compliance to
a specified minimum LBR value only, the two samples nearest optimum
moisture may be tested. If both samples satisfy the minimum LBR
requirements, the material may be reported as satisfying the specification,
and the remainder of the samples may be discarded. If, however, either
sample failed to meet the minimum specified LBR value, then the full LBR
curve should be determined as previously described.)
REPORT
FM 5-515
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September 1, 2000
The test results should be reported as shown on the sample page in Figure 8
consisting of:
9.1
A plot of the moisture-density curve giving the maximum dry density to the
nearest 10 kg/m3 (1 lbs/ft3) and optimum moisture content to the nearest
percent.
9.2.1
A semi-log plot of the LBR-moisture curve giving the maximum LBR value.
Metric Equivalents
0.0025 mm
0.025 mm
0.0001 in.
1.001 in.
1.6 + 0.8 mm
6.35 mm
9.52 mm
1/16 + 1/32 in
1/4 in.
3/8 in.
25.4 mm
35.8 + 0.51 mm
49.63 + 0.25 mm
1 in.
1.41 + 0.02 in.
1.95 + 0.1 in
52.4 mm
63.0 mm
73.7 mm
2-1/16 in
2-1/2 in.
2.9 in.
95.0 mm
149.2 mm
150.8 + 0.8 mm
3.75 in.
5-7/8 in.
5-15/16 + 1/32 in
151 mm
152.4 + 0.51 mm
152.4 mm
5-15/16 in
6 + 0.02 in.
6 in.
165 mm
1935 mm
2.27 kg
6-1/2 in.
3 in.
5 lb
4.5 kg
10 lb
The values above apply to Figures 1 through 6
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with 10 000 lb Capacity Proving Ring
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Figure 7 - Automatic Tester and Recorder
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