FM 5-472 Materials Testing (DEPARTMENT OF THE ARMY) December 2000 - page 5

 

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FM 5-472 Materials Testing (DEPARTMENT OF THE ARMY) December 2000 - page 5

 

 

FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
This would provide a density range, in pcf, from 110.3 to 116.4. This is
calculated in the following manner:
0.90 × 122.5 = 110.3 pcf
0.90 × 122.5 = 116.4 pcf
Using the range between 90 and 95 percent, these limits can be imposed on
the CBR family of curves by drawing two vertical lines, one at 110.3 and the
other at 116.4 pcf.
Step 13. Determine the assured CBR values between the specified density
limits. If the builder is allowed to place the soil between 110.3 and 116.4 pcf,
this step involves determining the CBR values obtained for each moisture
content. The change in CBR for any specific moisture-content line between
the two density limits shows that a range of strengths is possible. Since the
builder will be allowed to place the soil anywhere between the established
density limits, the CBR value selected as a potential design strength should
represent the worst case. Using 8 percent moisture as an example, the CBR
at 110.3 pcf is 15.6. At 116.4 pcf, the CBR is a maximum of 18.0. Of the two,
15.6 is the minimum strength for the specified density range. This procedure
was followed for the remaining moisture contents in the example, and the
results are recorded on page 4 of DD Form 2463 (see Figure 2-69, page 2-142).
Step
14.
Determine the CBR values for potential moisture-content
specification ranges. Like the density range, a moisture-content range that
can be economically achieved in the field is desired. Within the overall range
of investigation (OMC ± 4 percent), a smaller specification range giving the
greatest assured CBR will be determined. Experience shows that a 4 percent
range (± 2 percent) is a reasonable requirement; however, this span is not
intended to represent an absolute rule. A smaller range may be specified to
achieve a larger design CBR and a reduction in pavement thickness
requirements. This savings in pavement materials may be offset by increased
costs associated with the difficulties in meeting the more stringent
requirements. Conversely, for some soils an expanded moisture-content
specification may have little effect on the design CBR. The sample problem
uses a 4 percent specification range. One possible range is 6 to 10 percent. If
the engineer specified that the soil be placed within these limits, the worst
possible strength would be a CBR of 14.4. A continued analysis can be done
for the other possible 4 percent ranges, as shown on page 4 of DD Form 2463
(see Figure 2-69).
Step 15. Select the moisture-content range that gives the greatest assured
CBR. In steps 13 and 14, CBR values were selected assuming that the builder
will be allowed to place the soil anywhere between potential moisture content
and density specification limits. Now the desired set of limits is selected. The
tabulation in step 14 shows that the soil, if placed between 7 and 11 percent
moisture, will give the largest of the possible CBR values. Thus, 15.0 becomes
the design CBR. To ensure that a CBR of 15.0 is achieved, compaction must
be 90 to 95 percent MDD or 110.3 to 116.4 pcf.
TEST PROGRAM FOR SWELLING OR EXPANSIVE SOILS
There is a small group of soils which expand objectionably after being
compacted and saturated. This presents a problem in pavement design as this
Soils 2-147
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
expansion or swell can damage the structure through reverse settlement. The
measure of swell is expressed as a percentage of the initial sample height.
Objectionable swell is defined as that in excess of 3 percent of the initial
sample height. A soil’s expansive nature is mainly due to the type of clay
minerals present. For example, montmorillonitic clay consists of the smallest
and most highly charged particles found in nature. The combination of large
surface-area-per-unit volume and high surface charge causes a tremendous
affinity for water and the ability to expand or shrink as water is taken in or
removed from the soil.
Experience shows that the PI is an excellent indicator of expansive soils.
Although a high PI does not guarantee that the soil is expansive, critical soils
should be checked more closely for swell tendencies. See Table 2-16 for
suggested guidelines. Table 2-14, page 2-137, indicates that the potentially
expansive soils—by USCS classification—are CH, MH, and OH. The test
procedure to determine a design CBR for an expansive soil is similar to that
discussed for nonswelling soils, but the objective is different. For nonswelling
soils, the object is to find the greatest assured CBR value for some range of
densities and moisture contents. The object of the test program for expansive
soils is to find the moisture-content ranges that will prevent objectionable
swell and provide the highest-soaked CBR. Generally, the minimum swell
and the highest-soaked CBR occur at a molding moisture content higher than
the OMC.
Table 2-16. Swell potential
PI
Expansiveness
0 to 14
Not expansive
14 to 25
Marginal
25 to 40
Critical
40
Highly critical
Example
The following is an example of such a test for a CH soil. As most of the steps
are similar to those developed for the case of nonswelling soils, only
differences will be discussed.
Steps
Step 1. Establish the soil’s OMC. Determine a moisture range for CBR
investigation. The OMC ± 4 percent range of investigations as used for the
nonswelling soils may not apply. It will be necessary to prepare samples over
a wider range of moistures with most of the work being done on samples
higher than the OMC. Prepare samples over a range of the OMC ± 8 percent.
As illustrated later, much of the laboratory work done on samples dry of the
OMC is not essential.
Step
2.
Compact the samples within the moisture-content range of
investigation at different levels of compactive effort. As the type of soil being
tested will generally be cohesive and will have a CBR less than 20, Table 2-15,
page 2-138, indicates that compaction must be at least 90 percent MDD. An
upper limit can be established as expansive soils are very difficult to compact
2-148 Soils
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
at levels greater than 100 percent of MDD. Laboratory compactive efforts of
10, 25, and 56 blows per layer are adequate for nearly all cases.
Step 3. Soak the samples and measure the swell. This step deviates from the
same step for the nonswelling soil. For each sample, measure the expansion,
compute the percent of swell, and plot against the molding water content. As
an example, the triangular data point at 10 percent moisture on the swell data
curve (see Figure 2-69, page 2-139) was obtained as follows:
• Initial sample height = 4.60 inches.
• Final dial reading = 0.025 inches.
• Molding water content = 10.0 percent.
• Level of compactive effort = blows per layer.
• Free-swell index or percentage of swell = (0.025/4.60) x 100 = 0.5
percent.
Step 4. Plot the points on page 5 of the DD Form 2463 (see Figure 2-69, page
2-143).
NOTE: The example of page 5, DD Form 2463 provided in Figure 2-69
is based on data from the nonswelling soil type as explained in the
nonswelling program section. A plot of data for a swelling soil may
look slightly different than this example, as indicated in Figure 2-71.
Once the points are plotted, a curve is then usually fit to only the CE 56 data
points. The curve for a swelling soil (see Figure 2-71, page 2-150) shows that
this soil, if placed and compacted at molding moisture contents of 14 percent
or greater, will swell 3 percent or less.
Step 5. Perform CBR penetration tests and determine the corrected CBR for
each sample.
Step 6. Plot the data on graphs of dry density versus molding moisture
content and corrected CBR versus molding moisture content.
Step 7. Reformat the data on DD Form 2463, page 2 (Figure 2-69, page 2-140).
Step 8. Plot the CBR family of curves (DD Form 2463, page 3 (Figure 2-69,
page 2-141).
Step 9. Establish a density range at which soils will be placed in the field. If
no prior experience or benefit of a test strip is available, then the flow chart in
Figure 2-70, page 2-146, may be used. In this case, the minimum level of
compaction is 90 percent of MDD. Assuming a reasonable specification range
of 5 percent, the upper limit will be set at 95 percent MDD.
The actual density range is calculated as discussed in the previous example
for nonswelling soils. These calculated limits are then placed on page 3 of DD
Form 2463 by drawing two vertical lines on the CBR family of curves.
For example, if the MDD was determined to be 110, then the following
calculation would be performed to establish the actual density limits:
110 × 0.90 = 99 pcf
110 × 0.95 = 104.5 pcf
Soils 2-149
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Figure 2-71. Sample DD Form 2463, page 5
2-150 Soils
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Step 10. Determine the assured CBR values between the specified density
limits. As more than 3 percent swell is not acceptable, evaluation of the CBR
values at moisture contents less than 14 percent is needless. The CBR values
of the applicable moisture contents should range from 14 through 20. The
CBR values of the applicable moisture contents were determined to be the
amounts shown in Table 2-17.
Table 2-17. Determining CBR values for moisture-content
percentages for swelling soils
w
CBR
14
3.4
15
4.2
16
3.2
17
2.2
18
1.3
19
0.9
20
0.4
Step 11. Determine the CBR values for potential moisture-content specification
ranges. For this example the values shown in Table 2-18 were derived.
Step 12. Select the moisture-content range that gives the greatest design
CBR. Step 11 shows that the 14 to 18 percent range provides the greatest
CBR value. Thus, the design CBR value is 1.3. This value is obtained when
the soil is placed at a moisture content between 14 and 18 percent and a
density of between 99.0 and 104.5 pcf.
Table 2-18. Determining CBR values for potential
moisture-content ranges for swelling soils
w (range, in
CBR
percent)
14 to 18
1.3
15 to 19
0.9
16 to 20
0.4
Step 13. Analyze the results. Note that this design value was obtained at the
expense of strength. This technique does not provide for drying the soil to a
moisture content less than the amount of placement. Should such extreme
drying take place, excessive shrinkage and pavement failure might be
expected. However, it takes considerable effort to remove water from
expansive soils and such soils are normally protected from drying by the
overlying pavement. The first thing to consider when encountering an
expansive soil is testing another location. However, this is not always feasible,
and this technique does not allow for determination of a design CBR at which
swell is not excessive.
Soils 2-151
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Expansive soils can be chemically stabilized to allow building. Adding small
amounts of lime considerably reduces the potential for shrinkage and swell.
Soils stabilization is further discussed in Chapter 5 of this manual as well as
TM 5-822-14 and FMs 5-430-00-1 and 5-430-00-2.
TEST PROGRAM FOR FREE-DRAINING SOILS
Determining a design CBR for free-draining soils requires the least testing
of the three remolded laboratory test programs. Table 2-14, page 2-137,
gives the USCS classification and the uses of the soils in this group.
The ease in testing is due to the free-draining characteristics or lack of fines
in the soil. The CBR analysis sheet for borrow pit A shows that the density-
versus-moisture-content curves have a concave, upward shape and show
maximum densities between 7 and 9 percent moisture, depending on the
level of compactive effort (see Figure 2-72). For each curve, there is a
limiting or minimum moisture content (MMC) at which moisture above that
required to fill the voids after compaction is squeezed or drained from the
soil (shown by the triangle, square, or circle in Figure 2-72). The dashed
lines to the right of the MMC represent attempts to compact the soil in a
saturated condition, but the results after compaction are densities and
moisture contents at the limiting condition. This means that field
placement is relatively easy for such soils. To ensure the MDD for any level
of compactive effort, the only control measure necessary is to have more
water available than that required for the MDD at the appropriate level of
compactive effort. The corrected CBR-versus-molding-water-content curves
show the same pattern in relation to moisture content as the dry density.
Soils placed with a moisture content above the minimum moisture content
achieve the maximum CBR possible for that level of compactive effort. In
other words, moisture contents of loose soils above the limiting values have
little bearing on the strength of a soil after compaction. This makes
laboratory testing, field placement, and field control relatively easy matters.
Example
To arrive at a design CBR, the steps outlined in the previous examples will
again be followed.
Steps
Step 1. Establish the soil’s MMC at 56 blows per layer. It is obtained by
locating the moisture content at which the MDD is achieved on the
compaction curve. For this example, the MMC is 8 percent with a MDD of 120
pcf. To ensure that a free-draining soil is being tested, this curve should
display a MDD at a limiting or minimum moisture content.
Step
2.
Compact the samples at different levels of compactive effort.
Compaction curves must be made for three levels of compactive effort up to the
MMC. As free-draining soils are frequently represented by well- and poorly
graded sands and gravels with CBR values above 20, Table 2-15, page 2-138,
indicates a compactive effort in excess of 100 percent of maximum CE 56 dry
density. Therefore, 25, 56, and 72 blows per layer are usually used.
2-152 Soils
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
100
100
80
80
60
60
40
20
40
0
0
4
8
12
20
140
120
0
40
60
80
100
120
140
100
Molding dry density, in pcf
80
60
40
20
0
0
4
8
12
Molding water content (w)
in percent of dry weight
Figure 2-72. Plotted results for a free-draining soil, borrow pit “A”
Step 3. Soak the samples and measure the swell. Swell measurements are
not required, and soaking can be eliminated when it is determined that
saturation does not affect the strength.
Step 4. Perform CBR penetration tests. Only the samples at the limiting
moisture contents for each level of compactive effort need to be tested.
Normally, more than one sample at the limiting conditions will be made for
each level of compactive effort, and all should be tested.
Step 5. Plot the data on graphs of dry density versus molding moisture
content and corrected CBR versus molding moisture content. Only the plot of
dry density versus molding moisture content is required. The corrected CBR-
versus-molding-moisture-content graph is presented only for discussion.
Step 6. Plot the CBR family of curves. This graph can be condensed into a
single line. The three data points are obtained by plotting the corrected CBR
against the associated dry density at the limiting moisture content.
Soils 2-153
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Step 7. Establish a density range at which the soil will be placed in the field.
Using the criteria from Table 2-15, page 2-138, and noting that the CBR value
for this soil is usually always greater than
20, the minimum level of
compaction allowed is 100 percent of maximum CE 56 dry density. Because no
additional information is provided, specify 100 to 105 percent of maximum CE
56 dry density. The actual density range is as follows:
1.00 × 120.0 = 120.0 pcf
1.05 × 120.0 = 126.0 pcf
Step 8. Determine the design CBR and placement moisture content. The
CBR family of curves shows that the minimum CBR value achieved between
the density range is 70, which is achieved at 120 pcf. The placement moisture
content necessary to ensure that this strength is obtained is 8 percent or
greater.
Considerably greater CBR values can be achieved if more field compaction is
applied to the soil. If this is not too costly, it may be advantageous to specify
greater densities.
SECTION X. TECHNICAL SOILS REPORT
A good program for soils testing not only requires that careful and complete
tests be performed, but also that the tests be completed as quickly as possible
and that the data be presented in a clear, logical consistent manner. Therefore,
you must be familiar with the tests, the sequence of testing, and the
presentation of results.
SOILS TESTS REQUIRED
The tests required by any program depend on the type of construction being
planned. However, there are a number of tests run consistently on road and
airfield construction programs. A complete testing program should include
the following tests:
• Soils exploration (see Sections I and II).
• Compaction (see Section VII).
• Plasticity index (see Section VI).
• Particle-size analysis (see Section V).
• CBR (see Section IX).
• Trafficability (see FMs 5-430-00-1 and 5-430-00-2).
PURPOSE OF THE REPORT
The soil tests listed above are specific tests used to gain knowledge about the
control of soils during construction, including the—
• Suitability of subgrade and borrow materials.
• Degree to which soil can be compacted.
2-154 Soils
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
• Bearing value of the subgrade and borrow material under projected
future conditions.
• Location of ledge rock and groundwater table.
• Susceptibility to detrimental frost action.
Each test supplies the necessary data to answer questions based on
engineering evaluation of scientific data rather than a meaningless guess.
ORGANIZATION AND SCOPE OF THE TESTS
Because of the number of tests to be performed for a particular project, careful
planning may avert considerable delays in the presentation of the results.
List the tests required and their sequence in a manner that will permit
running the tests continuously, without delays due to time needed for soaking
or drying samples.
An example of the daily activities in a complete soil-testing program are listed
in Figure 2-73. Some testing programs may not include all the tests listed in
the example and soil types or test results may change the activity list. An
activity schedule for each unit may be different due to equipment and mission
priority.
The following paragraphs cite some considerations that may be helpful in
setting up a continuous soil testing program.
Sample Soils Laboratory Testing Schedule
Test/activity
Day
Day
Day
Day
Day
Day
Day
Day
1
2
3
4
5
6
7
8
Grain-size analysis
(sieve method)
Specific gravity
Plastic and liquid limits
Compaction
Laboratory CBR
Grain-size analysis
(hydrometer method)
Figure 2-73. Sample schedule for soils laboratory testing
Soils 2-155
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Exploration
Before any tests can be performed, representative samples of the soil involved
in a given project must be obtained. This, however, is only one objective of soil
exploration. Other considerations include plotting a profile of boring results,
locating ledge rock, determining the depth to the groundwater table,
determining field moisture content, and field-identifying the soils sampled.
Particle/Grain-Size Analysis
The mechanical analysis is another test that should be used to occupy periods
between other tests. The test is an evaluation of the grain-size distribution
used to establish the gradation of the soil sample. The sieve analysis and
hydrometer analysis may be used in obtaining the required information.
LL and PL Tests
One use of LL and PL test results is to predict how the fine-grained portion
(No. 200 fraction) will affect the engineering value of a particular soil sample.
This evaluation, obtained through soil classification, is to ensure that the
sample being tested meets specifications set on the LL and PL for the
particular project for which it will be used. These tests should be performed
while waiting for compaction-test moisture-content samples to dry and CBR
samples to soak or any time between other tests.
Compaction Test
The compaction test indicates the MDD that can be obtained practically in the
field. It also indicates the OMC at which this dry density can be obtained.
Since this will be a test used for control purposes, it should be run as soon as
possible. While moisture-content samples from this test are drying, tests for
plasticity and particle-size analysis can be started.
Laboratory CBR Test
The CBR test is determined by an arbitrary penetration procedure to obtain a
modulus of shearing resistance of a subgrade or base-course soil. This value is
used to determine the required thicknesses of the various base courses through
its application to empirically derived design curves. Because the procedure for
this test may involve a four-day soaking requirement, CBR samples should be
prepared as soon as the necessary information from the results of the
compaction test is available. This information may be obtained from
approximated values of the OMC.
Field In-Place CBR Test
The latest addition to equipment used for determining the CBR value of a soil is
the dual-mass DCP. The procedures for testing with the DCP and the
correlation of CBR values can be found in the user’s manual for the equipment
or in Annex J of FM 5-430-00-2.
SOILS TECHNICAL REPORT
In writing technical reports, one of the most important aids is a clear, logical
outline of the subject. Outlines will vary according to the program conducted
and the data required, but the suggested format that follows should help
organize a report.
2-156 Soils
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Frequently, portions of the information shown in the outline will be required at
different times.
For this reason, a preliminary report and several
supplementary reports may actually be made before the project is completed.
However, if all of the information provided follows the same basic outline, filing
the data and assembling the final report will be simplified.
PURPOSE
Use the following information to write a soils technical report that includes all
pertinent data given in the conditions and follow the recommended outline.
EQUIPMENT
Use the following items and information to write a soils technical report:
Soil boring logs.
The soil’s profile.
The soil’s field identification.
In-place moisture data.
Particle/grain-size analysis data.
LL and PL data.
The USCS laboratory soils classification.
CBR test data.
In-place density data (as required locally).
In-place CBR data.
A topographic map of the site.
Aerial photographs (if available).
Pencils.
Pens.
Paper.
The project directive.
FM 5-430-00-1.
OUTLINE
Use the following recommended outline to organize a technical soils report:
1. Project.
A. Description. What type of construction is being performed
(for
example, Class D road, base camp, and airstrip)?
B. Purpose and scope. Who is requesting construction? What is the
extent and why is it being performed?
2. Site description.
A. Location. All map references and directions including county or
province (if available).
Soils 2-157
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
B. Existing facilities. This could include many things such as old logging
roads, dirt paths, patrol roads, buildings, overhead power lines, and so
forth (see sketches).
C. Topography, cultivation, and drainage. Description of terrain features.
(forest, farmland, well drained, swampy, hills, and so forth).
D. Climate. Temperature extremes, seasonal precipitation, average wind
speed, and so forth.
3.
Geology.
A. Overburden. Main depositing force (river, glacial, and so forth), rock
classes (sedimentary, igneous, metamorphic), and depth of overburden.
B. Bedrock. Average depth to bedrock and state of bedrock, such as
faulted, fractured, or folded.
4.
Site conditions.
A. Field explorations. Details of performed tests, location of test sites,
and explanation of sample tags.
B. Field tests. Type of field tests performed and field sample results
(enclose copies in Annex G).
C. Laboratory tests. Type of laboratory tests performed. Do not include
MDD or laboratory CBR results.
D. Test results. Synopsis of test results and classifications. Refer to
forms in Annex F.
5.
Fill and borrow materials.
A. Field explorations. Details of performed tests, location of test sites,
and explanation of sample tags.
B. Field tests. Type of field tests performed and field sample results
(enclose copies in Annex G).
C. Laboratory tests. Type of laboratory tests performed. Do not include
MDD or laboratory CBR results.
D. Test results. Synopsis of test results and classifications. Refer to
forms in Annex F.
6.
Conclusions and recommendations.
A. Final site selection (if applicable). Exact location of finished project.
Refer to plans enclosed in Annex C.
B. Economical design. Low-cost or resource alternatives to current
suggestions (soil-cement, asphalt binder, chemical stabilization methods,
mats or fabrics, and so forth).
C. Minimum specifications. Design CBR, MDD, and OMC specifications.
Refer to laboratory forms in Annex F.
7.
Annexes.
A. Project directive and all directives involving this project.
2-158 Soils
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
B. General plan drawings (geology should be indicated).
C. Location plan drawings (existing and proposed features).
D. Profiles and cross sections.
E. Boring logs.
F. Laboratory testing data.
G. Field testing data.
NOTE: Not every subject will apply to every report. In many reports,
some of the items may be covered in several sentences, while others
may require a page of discussion. Some items (for example 5, 6, and
7) may have to be repeated for each runway in a major airfield. All
laboratory test forms will be included in Annex C. If a specific test
form is not necessary or not conducted, write the words
“Not
Applicable” across the form.
Soils 2-159
Chapter 3
Bituminous Mixtures
This chapter provides information on the materials used in constructing
bituminous surfaces, the methods of testing these materials, and the mixes
prepared from them. The design considerations—such as bearing capacity
and thickness of pavements—are described in FM 5-430-00-1. Mixing and
placing operations, as well as the considerations for preparing the mixes,
are described in TM 5-337..
SECTION I. BITUMINOUS PAVEMENTS/SURFACES
Bituminous pavements/surfaces are a mixture of mineral aggregates, mineral
filler, and a bituminous material or binder. This mixture is used as the top
portion of a flexible pavement structure to provide a resilient, waterproof,
load-distributing medium that protects the base course from the detrimental
effects of water and the abrasive action of traffic.
AGGREGATES
Mineral aggregates may consist of crushed rock, crushed or uncrushed soils
(including gravels and sands), slag, mineral filler, or a combination of some of
these materials. Other materials that may be used as aggregate in certain
geographical areas include vesicular lava and coral. Aggregates normally
constitute 90 percent or more by weight of bituminous mixtures, and their
properties greatly affect the finished product. The aggregate provides three
basic functions when used in bituminous surfaces:
• It transmits the load from the surface down to the base course. In
pavement, this is accomplished through the mechanical interlock of
the aggregate particles.
• It withstands the traffic’s abrasive action. If a wearing surface were
laid consisting of binder alone, it soon would be worn away by the
abrasive action of tires.
• It provides a nonskid surface. A portion of the aggregate extends
slightly above the normal surface of the wearing mat, thereby
providing a roughened surface for tires to grip.
BITUMINOUS MATERIALS
A bituminous material is the adhesive agent or binder in a bituminous
mixture. This material or binder provides two functions:
• It binds the aggregate together, holds it in place, and prevents
displacement.
Bituminous Mixtures 3-1
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
• It provides a waterproof cover for the base and keeps surface water
from seeping into and weakening the base material.
The binder’s functions require it to be a waterproof substance having the
ability to bind aggregate particles together. All bituminous materials possess
these qualities due to being mainly composed of bitumen—a black solid that
provides the black color, cementing ability, and waterproofing properties.
Bituminous materials are classified into two main groups—asphalts and tars.
They are available in several forms suitable for different procedures of mixing
or application under wide variations in temperature. Some bituminous
materials are solid or semisolid at room temperature. Other grades are a
relatively viscous (thick) liquid at room temperature. Mixing bituminous
materials with solvents or water produces cutbacks or emulsions that are
liquid at atmospheric temperatures. Such liquid asphalts and tars are used
for cold mixes or are applied as sprays in building pavements.
ASPHALTS
Asphalt is obtained only from crude petroleum and has two general classes—
natural and manufactured. Natural asphalts occur in lakes (as lake asphalt),
pits, or rock structures (as rock asphalt). Manufactured asphalt is produced
by distilling crude petroleum (see Figure 3-1). A military engineer is seldom
concerned with natural asphalts because they are not usually available in
those areas of interest. Therefore, this chapter discusses the uses and testing
of manufactured asphalts.
All asphalt cements are solid or semisolid at room temperature (77°F) and
must be converted to a fluid state by heating, emulsifying, or dissolving in a
petroleum solvent.
Grading
There are two grade scales used for identifying asphalt cement—penetration
grade and viscosity grade. The penetration grade is determined by the
distance a standard needle under a standard load will penetrate a sample in a
given time under a given temperature condition. A correlating asphalt-
petroleum number from 00 to 7 is assigned to these penetration ranges. The
viscosity grade is determined using a standard viscometer under standard
conditions. Table 3-1 lists the penetration ranges and correlating asphalt-
petroleum numbers presently recognized along with the relative consistencies.
Table 3-1.
Penetration grades and asphalt petroleum numbers of asphalt cement
Asphalt-Petroleum
Penetration Grade
Relative Consistency
Number
40 to 50
7
Hard
60 to 70
5
85 to 100
3
Medium
120 to 150
1
Soft
200 to 300
00
3-2 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Oil well
Field storage Pumping station
Light distillate
Processing
Gasoline
Light solvents
Medium distillate
Kerosene
Light burner oil
Heavy distillate
Diesel oil
Lubricating oils
Tube
Condenser
still
Storage
Residual material
Process
unit
Refinery
Liquid
asphaltic
materials
Asphalt
SC-70
Slow-
SC-250
curing
SC-800
Residual
asphalts
SC-3000
fuel oil
SC-
MC-30
MC-70
Medium-
MC-250
curing
MC-800
asphalts
Asphalt cements
MC-3000
Gas
Penetrating
RC-70
grades
Rapid-
RC-250
Asphalt
40-50
curing
RC-800
(air-
60-70
asphalts
Petroleum
RC-3000
refined)
85-100
SC-800
120-150
Emulsion
200-300
RS-1
Still
plant
Sand and water
RS-2
Anionic-
Oxidized
MS-2
emulsified
Air
asphalts
SS-1
asphalts
SS-1h
Emulsion
plant
RS-2K
RS-3K
Cationic-
SM-K
emulsified
CM-K
asphalts
SS-K
SS-Kh
Figure 3-1. Simplified flow chart showing recovery and refinement of
petroleum asphaltic materials
Bituminous Mixtures
3-3
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Cutback Asphalts
When heating equipment is not available or is impractical to use, asphalt
cement can be made fluid by adding solvents (called cutter stock or flux oils).
Cutter stock may be any one of the more volatile petroleum-distillate
products. The resulting combination is called asphalt cutback. Exposure to
air causes the solvents to evaporate and leave the asphalt cement to perform
its functions.
The classification of the cutback is based on the evaporation rate of the
distillate in the mixture. Gasoline or naphtha (high volatility) produces a
rapid-curing (RC) cutback; kerosene (medium volatility) produces a medium-
curing (MC) cutback; and fuel oil (low volatility) produces a slow-curing (SC)
cutback. Road oils, referred to occasionally, are a heavy petroleum oil in the
SC grade of liquid asphalt. Table 3-2 shows the percentage of components by
grade for the three types of asphalt cutbacks.
Table 3-2. Asphalt-cutback composition (expressed in percent of total volume)
Grades
Type
Components
30
70
250
800
3,000
Asphalt cement
65
75
83
87
RC
Gasoline or naphtha
35
25
17
13
Asphalt cement
54
64
74
82
86
MC
Kerosene
46
36
26
18
14
Asphalt cement
50
60
70
80
SC
Fuel oil
50
40
30
20
As more cutter stock is mixed with a given amount of asphalt cement, a
thinner liquid results. In practice, different amounts of cutter stock are added
to a given amount of asphalt cement to obtain various viscosities, or grades, of
cutbacks. The Corps of Engineers has approved a set of specifications for
cutbacks based on kinematic viscosity. The number assigned to each grade
corresponds to the lower limit of kinematic viscosity as determined by a
standard test. The upper limit of each grade is equal to twice the lower limit
or grade number. The units used in the test are centistokes.
Thus, a number 70 cutback refers to a viscosity range of 70 to 140 centistokes.
The other grades and their limits are 250 (250 to 500), 800 (800 to 1,600), and
3,000 (3,000 to 6,000). In addition, the MC has a 30 grade (30 to 60). Figure
3-2 shows the scale of viscosity grades. The higher the viscosity, the thicker
the liquid.
Asphaltic penetrative soil binder is a special cutback asphalt composed of low-
penetration-grade asphalt and a solvent blend of kerosene and naphtha. It is
similar in character to standard low-viscosity, MC cutback asphalt but differs
in many specific properties. It is used as a soil binder and dust palliative.
Asphalt Emulsions
It is often advantageous to use an asphalt material that is liquid at room
temperature and yet will not burn. Asphalt emulsions possess these
3-4 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
properties. Emulsified asphalt is a liquid material made up of a mixture of
asphalt, water, and emulsifier. Asphalt and water will not mix alone so a
chemical agent (an emulsifying agent) must be added. Common emulsifying
agents are soaps, colloidal clays, and numerous other organic agents.
Emulsified asphalt is a heterogeneous system in which water forms the
continuous phase of the emulsion and the minute globules of asphalt for the
discontinuous phase. There is also an inverted asphalt emulsion in which the
continuous phase is asphalt (generally liquid asphalt) and the discontinuous
phase is minute globules of water in relatively small quantities. Emulsified
asphalts may be of either the anionic (electronegatively charged asphalt
globules) or cationic
(electropositively charged asphalt globules) types,
depending on the emulsifying agent.
Emulsions are classified according to the setting or breaking rate which is the
speed at which the emulsion breaks or the asphalt and water separate. This
rate usually depends on the emulsifier used and the proportion of water to
asphalt. Emulsions are described as rapid-setting (RS), medium-setting (MS),
and slow-setting (SS) and also by viscosity numbers (see Figure 3-2). Because
of this breaking rate, emulsions can also be grouped according to their ability
to mix with damp aggregate. The RS emulsion breaks so fast that it cannot be
mixed; therefore, it is called a nonmixing type. The MS and SS emulsions
break slowly enough to permit good mixing until each particle of the aggregate
is uniformly coated. Emulsions may also be satisfactorily used as a tack coat
for bituminous pavements.
Figure 3-2. Viscosity grades at room temperature
Bituminous Mixtures 3-5
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
TARS
Tars are products of coal distillation (see Figure 3-3). No natural source of tars
exists. Coal tar is a general term applied to all varieties of tar obtained from
coal. It is produced by one of several methods, depending on the desired end
product.
When bituminous coal is destructively distilled, coke and gas are formed. Tar,
ammonia, light oils, sulfur, and phenol may be recovered. Coke-oven tar is
Figure 3-3. Simplified flow chart showing production of road tars from bituminous coals
3-6 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
produced in the greatest amount. Its chemical, physical, and adhesive
characteristics make it most suitable for road-tar purposes. Water-gas tar is
obtained in the manufacture of carbureted water gas. The nature of the
carbureting oil largely determines the character of the water-gas tar produced
and may vary widely in specific gravities, viscosities, and other physical and
chemical properties.
Road tars are manufactured in 12 grades of viscosity (see Figure 3-2, page
3-5). There are also some special grades for use in rubberized-tar binders.
Grades 1 through 7 are liquid at room temperature, while grades 8 through
12 are semisolid or solid. The difference is due to the liquid coal distillates
in the tar; the more distillate, the more liquid (or less solid) the tar. The
road-tar cutbacks (RTCBs) are products of cutting back the heavier or
harder grades with coal-tar distillates. RTCBs are manufactured in two
viscosity grades (5 and 6) only.
Tar, which is insoluble in petroleum distillates, is sometimes mixed with oil-
resistant, unvulcanized rubber to form a rubberized-tar binder material.
CHARACTERISTICS AND USES OF BITUMENS
Tables 3-3 and 3-4, pages 3-8 through 3-11, list the bituminous materials,
sources, curing, temperatures, and grades associated with bituminous
operations.
SAFETY PRECAUTIONS
Be extremely cautious when handling bituminous materials. Asphalt cement,
which is solid at room temperature, is heated to high temperatures to make it
workable as a binder material. Heated asphalt can cause severe burns if
allowed to come in contact with the skin. The vapors emitted by heating
bituminous materials may be harmful if inhaled. Use care during heating to
ensure proper ventilation. Asphalt cutbacks contain highly flammable
volatiles. The vapors will ignite at relatively low temperatures. The lowest
temperature at which they will ignite is called the flash point. The minimum
flash point for RC-250, RC-800, and RC-3,000 is 80°F; for MC-30 and MC-70,
about 110°F; for MC-250 to MC-3,000 and SC-70, about 150°F; and for the
remaining SC grades, about 25° higher per grade up to 225°F for SC-3,000.
NOTES:
1. The spraying and mixing temperatures in many cases are above
the flash point (see Table 3-3). Use extreme caution when handling
these mixtures. Do not expose their vapors to an open flame.
2. Cutbacks may also be classified as an environmentally hazardous
material.
Check with unit and installation environmental
representatives for further guidance as to proper storage, use, and
disposal of these substances.
If your unit’s environmental
representative is not known, consult your commander for assistance.
Bituminous Mixtures 3-7
Table 3-3. Characteristics of bituminous materials
Temperature of Application Ranges
Flash Point
Grade
Material
Form
Designa-
Spraying **
Mixing
(Min)
Remarks
tion
°F
°C
°F
°C
°F
°C
Penetrative soil
Contains naphtha
Liquid
130-150
55 - 65
80
27
binder
Caution: Highly flammable
*105-
RC cutbacks contain highly-
175
Liquids—asphalt
*41-79
volatile naphtha cutter stock.
RC-70
145-
95-135
35-57
residues fluxed
63-104
Naphtha evaporates quickly,
RC-250
220
135-175
57-79
80
27
Cutback (RC)
with more volatile
*82-124
leaving an asphalt-cement
RC-800
180-
170-210
77-99
80
27
petroleum
*102-
binder, permitting early use of
RC-3,000
255
200-240
93-116
80
27
distillate
143
the surface.
*215-
Caution: Highly flammable
290
Liquids—asphalt
MC-30
70-140
21-60
55-95
13-35
100
37
MC cutbacks contain less
residues fluxed
MC-70
105-175
41-79
95-135
35-57
100
37
volatile kerosene cutter stock.
Cutback (MC)
with more volatile
MC-250
145-220
63-104
135-175
57-79
150
65
Kerosene evaporates less
petroleum
MC-800
180-255
82-124
170-210
77-99
150
65
rapidly than naphtha.
distillate
MC-3,000
215-290
102-143
200-240
93-116
150
65
Caution: Flammable.
Liquids—asphalt
SC cutbacks contain slightly-
SC-70
105-175
41-79
95-135
35-57
150
65
residues fluxed
volatile diesel-fuel cutter
SC-250
145-220
63-104
135-175
57-79
175+
79+
Cutback (SC)
with more volatile
stock. Diesel fuel evaporates
SC-800
180-225
82-124
170-210
71-99
200+
93+
petroleum
slowly.
SC-3,000
215-290
102-143
200-240
93-116
225+
107+
distillate
Caution: Flammable.
Penetrations 40 to 100 used
40-50
300-350
149-177
for crack and joint fillers.
60-70
285-350
141-177
275-325
135-163
Penetrations 70 to 300 used
Asphalt cements
Solids
85-100
285-350
141-177
275-325
135-163
for plant mixes, penetration
120-150
285-350
141-177
275-325
135-163
macadam, and surface
200-300
260-325
127-163
200-275
93-135
treatment. Use test to
determine flash point.
Hard and solid
Powdered
Used with SC to produce
asphalts ground
asphalt
extra tough road surfaces.
to powder
* RC cutbacks are seldom used for spraying.
** Low temperature is based on a viscosity of 200 centistokes kinematic viscosity and the higher temperature is based on a 50-centistoke
viscosity.
Li id
h l
Table 3-3. Characteristics of bituminous materials (continued)
Grade
Temperature of Application Ranges
Flash Point
Material
Form
Designa-
Spraying **
Mixing
(Min)
Remarks
tion
°F
°C
°F
°C
°F
°C
Liquids—asphalt
Freezing destroys emulsion.
particles held in
RS-1
50-140
10-60
Nonmixing
10-60
Use for road and plant mixes
Asphalt
an aqueous
RS-2
50-140
10-60
50-140
10-60
with coarse aggregates (SS).
emulsions (RS)
suspension by an
RS-2K
50-140
10-60
50-140
10-60
All emulsions with “K” suffix
emulsifying
RS-3K
50-140
10-60
50-140
10-60
are cationic.
agent
Liquids—asphalt
particles held in
MS-2
50-140
10-60
50-140
10-60
Asphalt
an aqueous
SM-K
50-140
10-60
50-140
10-60
emulsions (MS)
suspension by an
CM-K
50-140
10-60
50-140
10-60
emulsifying
agent
Liquids—asphalt
particles held in
SS-1
50-140
10-60
50-140
10-60
Asphalt
an aqueous
SS-1h
50-140
10-60
50-140
10-60
emulsions (SS)
suspension by an
SS-K
50-140
10-60
50-140
10-60
emulsifying
50-140
10-60
50-140
10-60
SS-Kh
agent
RT-1
60-125
15-52
Priming oils. RT-4 through
Road tars
Liquids
RT-2
60-125
15-52
RT-12 not generally used.
RT-3
60-125
27-66
RTCB-5
60-120
16-49
Patching mixtures.
RTCBs
Liquids
RTCB-6
60-120
16-49
Caution: Flammable.
Mixed and used locally where
Rock asphalt
Solids
found. Cutback may be
added if necessary.
* RC cutbacks are seldom used for spraying.
** Low temperature is based on a viscosity of 200 centistokes kinematic viscosity and the higher temperature is based on a 50-centistokes
viscosity.
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Table 3-4. Typical uses of bituminous materials
Grade or Designation1
Purpose or Use
CB - Asphalt Cutback2
RC
MC
SC
MC-30, -70, -250
Dust palliative
DCA-703
SC-70, -250
APSB4
Prime coat:
Tightly bonded surfaces
MC-30
Loosely bonded, fine-grained surfaces
MC-70
SC-70
Loosely bonded, coarse-grained
MC-250
SC-250
surfaces
Tack coat
RC-250, -800
MC-250, -800
Surface treatment and seal coat:
Coarse sand cover
MC-250, -800
RC-70, -250
Clean coarse aggregate cover
MC-800
RC-250, -800,
Graded gravel aggregate cover
MC-250-, -800
SC-800
-3,000
Gravel mulch
MC-250
SC-250
Mixed in place road mix:
Open-graded aggregate:
Sand
RC-70, -250
MC-800
Maximum diameter 1 inch, high
MC-800
percentage passing No. 10
Macadam aggregate
RC-250, -800
Dense-graded aggregate:
High percentage passing No. 200
MC-250
SC-250
Maximum diameter 1 inch, medium
MC-250, -800
SC-250, -800
percentage passing No. 200
Premix or cold patch:
Open-graded aggregate
RC-250
MC-800
SC-800
Dense-graded aggregate
MC-250
SC-250
Cold-laid plant mix:
Open-graded aggregate:
Sand
RC-250, -800
Maximum diameter 1 inch, high
RC-800
SC-800
percentage passing No. 10
Macadam aggregate
RC-800, -3,000
Dense-graded aggregate:
High percentage passing No. 200
Maximum diameter 1 inch, medium
percentage passing No. 200
Aggregate precoating followed with
asphalt
1Prevailing temperature during construction also affects selection of bitumen and may be the
determining factor rather than size and gradation of aggregate.
2Caution: Do not overheat aggregate when cutbacks are used to produce hot mixes.
3DCA-70 is a water emulsion of a polyvinyl acetate containing chemical modifiers (formerly UCAR-
131). Proprietary product of Union Carbide Corporation, New York, NY.
4Asphaltic penetrative soil binder (APSB)
3-10 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Table 3-4. Typical uses of bituminous materials (continued)
Grade or Designation1
Purpose or Use
CB - Asphalt Cutback2
RC
MC
SC
MC-30, -70, -250
Dust palliative
DCA-703
SC-70, -250
APSB4
Hot-laid plant mix
RC-3,000
MC-3,000
SC-3,000
Penetration macadam:
Cold weather
RC-800, -3,000
SC-3,000
Hot weather
1Prevailing temperature during construction also affects selection of bitumen and may be the determining
factor rather than size and gradation of aggregate.
2Caution: Do not overheat aggregate when cutbacks are used to produce hot mixes.
3DCA-70 is a water emulsion of a polyvinyl acetate containing chemical modifiers (formerly UCAR-131).
Proprietary product of Union Carbide Corporation, New York, NY.
4Asphaltic penetrative soil binder (APSB).
ADVANTAGES AND DISADVANTAGES
Advantages and disadvantages of the bituminous materials used in
construction are as follows:
Asphalt-cement cutbacks are flammable. Asphalt pavements are susceptible to
damage by the blast from jet planes, and they can be dissolved by petroleum
products that may be spilled on them such as during refueling at an airfield.
Tars, on the other hand, are not affected by petroleum derivatives since they are
products of coal. Tars, when used as a prime for base courses, seem to possess
better penetration qualities than asphalts and are less susceptible to stripping
(loss of bond to aggregate) in the presence of water. Tars are affected by
temperatures and have a wide range in viscosity with normal surrounding
temperature changes. Tar can become so soft during warmer weather that the
pavement will rut under traffic. In colder weather, it can become so brittle that
the pavement will crack. The temperature susceptibility of tar binders is
improved by blending with oil-resistant rubber. Asphalt pavements and tar
pavements are generally ready for traffic within a few hours after placement
since they can be used as soon as they reach normal temperature.
Asphalt emulsions are not flammable and are liquid at normal temperatures.
Since they are mixed with water, they can be used with more damp aggregate
than required for the cutbacks. Additional water may be added to the emulsion
up to proportions of 1:3 for use in slurry seal coats. Because emulsions contain
water, they have certain disadvantages. During freezing weather, the
emulsions can freeze and the components separate. Emulsions are difficult to
store for extended periods because they tend to break even in unopened drums.
When shipped, the water in the emulsion takes up valuable space which could
be used to transport hard-to-obtain materials.
Bituminous Mixtures 3-11
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
SECTION II. SAMPLING MATERIALS
When conducting tests, use the materials that represent those that will be
used in construction; otherwise, test results will be misleading. Sampling of
materials for testing should receive close attention. When large samples must
be subdivided into small units for the actual tests, take care to keep the
sample representative of the original mass. Reduce aggregate samples to the
proper size for testing by means of quartering. Methods for sampling natural
deposits of sands and gravels are discussed in soil surveys and are applicable
here.
Take samples of bituminous materials at the place of manufacture or at the
delivery point.
(This manual assumes that sampling is done at the point of
delivery.) Samples may be taken for either of two purposes:
• To obtain an average of the delivered material.
• To find the maximum variation in the material's characteristics.
Take samples for analysis to identify bituminous materials if records are not
available. Obtain sufficient quantities of materials at the time of sampling to
meet specification requirements and to provide for laboratory pavement-
design tests. Normally, aggregates that will produce 150 pounds of the desired
gradation and 2 gallons of bituminous material will produce sufficient data.
BITUMINOUS MATERIALS SAMPLING (ASTM D 140-88)
Use clean, dry containers for sampling. Keep the containers tightly closed and
properly marked. A sample for a routine laboratory examination should not
be less than one quart.
LIQUID MATERIALS
When sampling liquid bituminous materials from nonagitated vertical tanks,
take samples from near the top, middle, and bottom. Test the samples from
the three levels separately to detect stratification. Materials shipped in tank
cars may be sampled from valves and taps. Take samples from drain cocks on
the side of the tank or car. If cocks are not present, take the samples by
lowering weighted bottles or cans into the material (see Figure 3-4). Fit the
bottle or can with a stopper that can be removed by a string or wire after it
has been lowered to the proper depth.
SOLID AND SEMISOLID MATERIALS
When sampling solid or semisolid materials in drums, barrels, cartons, and
bags, take samples at least 3 inches below the surface and 3 inches from the
side of the container or cake. Use a clean hatchet on hard material and a stiff
putty knife on soft material.
AGGREGATE SAMPLING (ASTM D 75-87)
Aggregate varies in size from the larger stones or rocks to the gravels and
sands. These materials for paving may still be in their natural deposits or
may be in stockpiles previously gathered.
3-12 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
NOTE: A wide-mouthed
glass bottle can be
Approx 1 1/2”
improvised, using wire or
rope sling
Cork with
Wire or rope lines
wire hook
Sample bottle
Weight
Approx 5”
Metal sample bottle
Approximate sample locations
Figure 3-4. Sampling liquid bituminous materials from tank car or storage tank
STONE FROM LEDGES AND QUARRIES
Obtain separate samples of unweathered stone weighing at least 50 pounds
each from all strata that appear to vary in color and structure. Prepare a
sketch plan with elevation, showing the thickness, length, width, and location
of the different layers so that the quantity available can be estimated.
NATURAL DEPOSITS OF SAND AND GRAVEL
Select samples that represent the different materials available in the deposit.
Sketch the area and indicate the approximate quantities of different
materials. If the deposit is an open-face bank or pit, take the sample by
channeling the face so that it will represent material that visual inspection
indicates may be used. Cut the face immediately before sampling, and discard
any material that has fallen from the surface along the face. Do not include in
the sample any overlying material (overburden) that is not suitable for use as
an aggregate, since this material would be stripped away when the aggregate
is removed from the pit. It may be necessary to make test borings or dig test
pits to determine the approximate extent of the material. If test pits are dug,
they must be adequately shored to prevent material from caving in on
personnel working in the pit. Obtain from the pit representative samples for
each change in strata. If the material being sampled is all sand, about 25
pounds is sufficient for tests. If it consists of sand and gravel, a somewhat
larger sample (about 75 pounds) is required for preliminary tests. The coarser
the gravel portion, the larger the sample required.
Bituminous Mixtures 3-13
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
STOCKPILES
If the material has been stockpiled previously, take care in obtaining samples.
There is a natural tendency toward separation of similar size fractions into
groups in the stockpile. The material near the outer edges and near the base
of the pile is likely to be coarser than the average. Cut a face into the stockpile
near the base, the center, and the top on at least two opposite sides. Combine
samples from at least three different sections of the pile to give a
representative sample.
COMMERCIAL AGGREGATES
It is preferable to obtain samples of commercial aggregates at the plant,
during loading, from stockpiles or bins. Obtain separate samples at different
times while the material is being loaded, to determine variations in the
grading of the material. Take bin samples from the entire cross section of the
flow of material as it is being discharged. Testing separate samples gives a
better idea of variations that occur, but samples should be mixed and reduced
by quartering when the average condition is desired. When it is not
practicable to visit the plant to obtain samples, the next preferred method is to
sample the material in cars or trucks or while it is being unloaded. Take
railroad-car samples from three or more trenches dug across the car at points
that appear on the surface to be representative of the material. When
obtaining the sample, remember that segregation of the different sizes has
probably taken place and choose samples that are representative.
SECTION III. FIELD IDENTIFICATION
Laboratory tests conducted on bituminous materials to check compliance with
specifications are not considered field tests. They are described in this section
for information purposes only. The field tests discussed in this section are
limited to the bitumen identification procedures, flash-point tests, and
penetration tests. These tests are applicable to both tars and asphalts and are
conducted to determine safe uses for a material.
Field identification enables the military engineer to determine the type of
surface that can be constructed with the type and grade of material available.
With the type of surface known, the construction procedure may be outlined
and scheduled. This procedure will then determine the proper equipment and
the necessary safety procedures.
The aggregate materials must also be tested for acceptable bituminous
construction use.
BITUMEN FIELD-IDENTIFICATION TESTS
Perform field tests to identify the bituminous paving materials as asphalt
cement, asphalt cutback, asphalt emulsion, road tar, or RTCB. In addition,
identify the viscosity grade of the bitumen. To distinguish among the several
asphaltic and tar products, it is necessary to know something of their origin,
physical properties, and the manner in which they are normally used. Some
of this information is contained in Tables 3-3 and 3-4, pages 3-8 through 3-11.
3-14 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
The identification procedure outlined in Figure 3-5 is based on a consideration
of the physical properties of these materials.
Unknown bituminous materials
Solubility test
Dissolves
Beads
Strings
asphalt
emulsions
tar
Color test
Water-mixing test
Flame test
Stone-coating test
Will not mix
Will mix
RS
MS or SS
Pour test
Pour test
1-3
4-7
8-12
RT
RT
RT
Will not pour
Will pour
Asphalt cement
Asphalt cutback
(Determine viscosity 30 - 3,000)
Smear test
Oily
Tacky
Penetration test
RTCB
RT
40-85
85-150
150-300
Hard
Med
Soft
Smear test
Tacky
Oily
RC
MC or SC
Heat odor test
Definite kerosene odor
No odor
MC
SC
Figure 3-5. Identification of unknown bituminous materials
Bituminous Mixtures 3-15
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Ensure that all tests are performed away from open flames and in well-
ventilated areas. Also ensure that all materials are properly disposed of
according to local environmental policy.
ASPHALTS AND TARS
The first procedure in identifying an unknown bituminous material is to
determine, by a solubility test, whether it is an asphalt or a tar. Attempt to
dissolve an unknown sample (a few drops, if liquid, or enough to cover the
head of a nail, if solid) by stirring it in any petroleum distillate. Kerosene,
gasoline, diesel oil, or jet fuel is suitable for this test. Since asphalt is derived
from petroleum, it will dissolve in the petroleum distillate. Road tar will not
dissolve. If the sample is an asphalt, the sample distillate mix will consist of a
dark, uniform liquid. Asphalt cements or cutbacks dissolve completely.
Asphalt in emulsions is also distinguishable as it dissolves and forms black
beads or globules in the bottom of the container of distillate. A road-tar
sample will be a dark, stringy, undissolved mass in the distillate. A check can
be made by spotting a piece of paper or cloth with the mix. Asphalt dissolved
in distillate will produce a brown to black stain. The clear distillate above the
settled tar will not cause a stain. The solubility test provides a positive
method of identification.
ASPHALT CEMENT AND CUTBACKS
Perform the following procedure to determine if the specimen is an asphalt
cement or a cutback.
The various grades of asphalt cement are solid at room temperature while
cutbacks are liquid, and a pour test will distinguish between them. Place a
sample of the material in a small container and attempt to pour it. If the
material does not pour, it is an asphalt cement. If it pours, it is a cutback or
an emulsion. Note that at 77°F even the softest asphalt cement will not pour
or deform if the container is tilted.
The various grades of asphalt cement are distinguished principally by their
hardness, as measured by a field penetration test. The information obtained
may be sufficient for planning for or starting emergency construction. The
exact penetration grade is not determined, but the field test will distinguish
between hard, medium, or soft groups of asphalt cement. Perform the test by
pushing a sharpened pencil or nail into the container of asphalt (at about
77°F) using about 10 pounds of force. If only a slight penetration is made with
considerable difficulty, a hard asphalt cement is present. If the penetration is
made with some difficulty, a medium asphalt cement is present. If the
penetration is made with ease, the asphalt cement is a soft asphalt cement in
the high-penetration scale. Even the highest penetration will not pour or
deform at 77°F if its container is tilted.
ASPHALTIC-CUTBACK TESTS
There are three tests used to determine the grade of an asphaltic cutback:
Pour Test
As stated previously, an asphalt cement will not pour at 77°F, but a cutback
will. The pour test can be used to determine whether the unknown material is
3-16 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
an asphalt cutback. If the material pours, it is an asphalt cutback. The
approximate viscosity grade number of the cutback is found by comparing the
flow to well-known materials such as water, syrup, and others. If this test is
made at a temperature below 77°F, the materials will appear more viscous
(stiff) than at 77°F and the opposite if tested when warmer than 77°F. The
cutbacks of a given viscosity grade will pour in a manner similar to the
following:
30—water.
70—light syrup.
250—syrup.
800—molasses.
3,000—barely deform.
After the pour test, the approximate viscosity grade of the cutback is known,
but the type (RC, MC, or SC) is not.
Smear Test
Perform the smear test to determine if a cutback is an RC. This is done by
making a uniform smear of the substance on a piece of glazed paper or other
nonabsorbent surface. Volatile materials, if present, will evaporate. Since RC
materials are cut back with a very volatile substance, most of the volatiles will
evaporate within
10 minutes. The surface of the smear then becomes
extremely tacky. This is not true of the lighter grades (MC and SC), which
remain fluid and smooth for some time. An MC will not result in a tacky
surface for a matter of hours. SC materials may require several days.
Perform a prolonged smear test to identify an 800- or 3,000-grade MC or SC
cutback. This is necessary because these grades contain such small quantities
of cutter stock that they may become tacky in the 10-minute period specified
above. Place a thin smear of the material on a nonabsorbent surface and let it
cure for at least 2 hours. By the end of that time, if the material being tested
is not an MC or SC, the smear will be hard or just slightly sticky. However, if
the material being tested is an MC or SC, the smear will be uncured and still
quite sticky. If the material is an RC-3,000, it will cure completely in 3 hours,
whereas an RC-800 will take about 6 hours to cure. Even after 24 hours, an
MC or SC will still be sticky.
Heat-Odor Test
The main difference between MC material and SC material is that the MC
material is cut back with kerosene and the SC with diesel or a low-volatility
oil class. In this test, apply heat to the sample to drive off the kerosene, if it is
present, and make it show up in the form of an odor. Heat the unknown
sample in a closed container to capture the escaping vapors, using minimal
heat. An MC sample will have a strong petroleum or kerosene odor. An SC
sample will have no kerosene or petroleum odor but may have a faint odor of
hot motor oil. The ability to differentiate between the RC, the MC, and the SC
is an essential part of field identification.
Bituminous Mixtures 3-17
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
ASPHALT-EMULSION (ANIONIC) TESTS
Another asphaltic material used in paving is asphalt emulsion, which is a
mixture of asphalt, water, and an emulsifying agent. The anionic emulsions
specifications cover three types of asphalt emulsion—RS grades 1 and 2, MS
grade 2, and SS grades 1 and LH.
Solubility Test
The solubility test will make an emulsion’s identity known by forming into
globules or beads that fall to the bottom of the container of petroleum
distillate. During this test, the emulsion will present a distinctive dark brown
color while all other bituminous materials are black.
Water-Mixing Test
If mixed with water, an emulsion will accept the extra water and still remain a
uniform liquid. The sample and water will mix uniformly if the material is an
emulsion. This test is positive since no other bituminous material will mix
with water.
Flame Test
Since an emulsion contains water, a small piece of cloth saturated with it will
not burn if a flame is applied. The other bitumens will burn or flame.
Stone-Coating Test
After establishing that the material is an emulsion, determine whether the
emulsion is a mixing grade (MS or SS) or a nonmixing grade (RS). Mix a
small amount (6 to 8 percent by weight) with damp sand using a metal spoon.
Exercise care not to add so much emulsion to the sand as to saturate it. An RS
emulsion will break so quickly it will not be possible to mix it with sand. It
breaks immediately, gumming up the spoon with the relatively hard original
asphalt cement. On the other hand, if the sample is a MS or SS emulsion, the
material will mix easily and coat all the particles completely (as well as the
mixing spoon) with a uniform coating of asphalt.
ROAD-TAR TESTS
There are three tests for road tars—the solubility test, the pour test, and the
smear test.
Solubility Test
As determined earlier, if the unknown bituminous material does not dissolve
during the solubility test but forms a stringy mass, the material is a tar (see
Figure 3-5, page 3-15). The next step is to determine its viscosity grade.
Pour Test
By comparing the flow of the material to that of common materials (see Figure
3-3, page 3-6), the viscosity of the tar may be closely estimated. The grades
run from RT-1 to RT-12 and vary in consistency from very fluid to solid.
Smear Test
If, during the pour test, the identified tar seems to be in the range of an RT-4
to RT-7 material, perform a smear test to determine whether it is a road tar or
3-18 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
an RTCB. Perform the smear test in the manner previously described for
cutback asphalt. The material is a road tar if the material remains with the
same amount of stickiness. If it shows a great increase in stickiness in 10
minutes, it is an RTCB. If field identification yields a grade of about 5 or 6, it
is not of particular importance specifically which grade of cutback it is since
both are used under approximately the same conditions.
AGGREGATE IDENTIFICATION AND SELECTION
Identify the aggregate by shape or roughness, hardness, cleanliness,
hydrophobicity, gradation, and particle size. Select aggregate with the best
combination of these characteristics. Also consider the availability, length of
haul, and overburden.
SHAPE AND ROUGHNESS
The aggregate in a pavement must transmit the traffic load to the base,
usually by the interlocking of the particles. This interlocking is much more
pronounced when the particles are angular in shape and rough in surface
texture. If angular pieces of aggregate are in a pavement, the individual
particles will not slip or slide over one another, but will lock together.
However, more binder may be required since the angular shape has a greater
surface area per unit volume than a round particle. Although angular
particles are desired, the aggregate should not contain an excessive number of
flat or elongated particles, as these particles cause bridging, thereby making
compaction difficult.
Aggregates very seldom occur in nature as angular, so it is necessary in most
cases to crush the aggregate to obtain the desired angular particles.
HARDNESS AND DURABILITY
The aggregate must be able to withstand the applied loads without cracking
or being crushed. Resistance to weathering is also a function of the durability.
An aggregate's resistance to wear can be determined by the Los Angeles
abrasion test. The Mohs hardness scale may be used to determine the
hardness of the aggregate. This scale is fully explained in FM 5-410. It
ranges from 1 for talc or mica to 10 for diamond. By trying to scratch the
aggregate or the common material, it is possible to establish which is harder;
this determines the hardness of the aggregate. If both are scratched, the
hardness of both is the same. Rub the scratch mark to see that it is really a
scratch and not a powdering of the softer material. Some common materials
and their approximate level of hardness are as follows:
• Fingernail—2.0.
• Copper coin—3.5.
• Knife blade—5. 0.
• Window glass—5.5.
• Steel file—6.5.
Bituminous Mixtures 3-19
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
CLEANLINESS
The bituminous binder must penetrate into the pores of the aggregate and
also adhere to the surface of the particles. Aggregates coated with clay or dust
or having water-filled pores prevent the penetration or the adherence of
bitumen and result in stripping of the binder. If the aggregate is not clean, it
should be washed, either as part of the crushing operation or by spreading it
on a hard surface and hosing it with water. When washing is impractical, dry
screening may remove a great deal of dust and clay. Handpicking may have to
be done if no other method can be used. The aggregate should be made as
clean as possible with the equipment and manpower available.
HYDROPHOBICITY
Affinity for water can make an aggregate undesirable. If the aggregate is
porous and absorbs water easily, the binder can be forced out of the pores, the
bond between the aggregate and binder can weaken and break, and stripping
can occur. Stripping is the loss of bituminous coating from the aggregate
particles due to the action of water, leaving exposed aggregate surfaces. One
of the following tests can be used to determine the detrimental effect of water
on a bituminous mix:
• The stripping test.
• The swell test.
• The immersion-compression test.
Stripping Test (ASTM D 1664-80)
Prepare a test sample by coating a
100-gram aggregate sample with
bituminous material at the right temperature for the grade of bitumen to be
used. Spread the mixture in a loose, thin layer and air-cure it for 24 hours.
Place a representative sample in a jar (no more than half full) and cover it
with water. Close the jar tightly and allow it to stand 24 hours. At the end of
24 hours, vigorously shake the jar with the sample for 15 minutes. Make a
visual examination to determine the percentage of exposed aggregate surface
and report it as the percent of stripping.
Swell Test
Asphaltic mixtures containing fines of doubtful quality are sometimes
measured for swell as a basis for judging the possible effects on a pavement.
This test is more frequently used with dense-graded mixtures using
emulsified and cutback asphalts. Compact a sample of the mix in a metal
cylinder
(usually
100 millimeters in diameter), and cool it to room
temperature. Obtain a height measurement for the specimen. Place the
specimen and mold in a pan of water, and mount a dial gauge above the
sample in contact with the surface. Take an initial reading. Allow the
specimen to soak for a specified period (usually 24 hours) or until there is no
further swelling. Take another dial reading. The difference in readings,
divided by the original height and expressed in percent, is the swell of the
mixture. Experience has shown that bituminous pavement made with clear,
sound stone; slag; or gravel aggregate and mineral filler produced from
3-20 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
limestone will show test values of swell of less than 1.5 percent of the original
specimen thickness.
Immersion-Compression Test (ASTM D 1075-88)
This test is intended to measure the loss of Marshall stability resulting from
the action of water on compacted bituminous mixtures containing
penetration-grade asphalt. The result is a numerical index of reduced
stability obtained by comparing the Marshall stability with the stability of
specimens that have been immersed in water for a prescribed period. Prepare
six standard Marshall specimens (4 inches in diameter and 2 1/2 ± 1/16 inches
high) for each test. Determine the specific gravity of each specimen. Separate
the set of eight into two sets of four so that the average specific gravity of one
set is essentially the same as the other. Test one set using the Marshall
method. Immerse the other set in water (at 140°F ± 1°) for 24 hours and then
test it. Compute the result as a ratio of soaked stability to unsoaked stability,
and express it as a percentage as follows:
S2
index or reduced stability
= ----- × 100
S
1
where—
S1 = average stability of unsoaked specimens
S2 = average stability of soaked specimens
Mixes with an index of less than 75 percent are rejected or an approved
method of processing aggregate and treating asphalt is required to increase
the index to a minimum of 75 percent.
GRADATION
The following designations help identify aggregates:
• Uniform gradation occurs when all particles are about the same size,
normally less than 1 inch.
• Macadam gradation consists of uniformly sized particles except that
they are in excess of 1 inch.
• Open gradation involves a considerable range of particle size, from
large to small, usually containing little or no mineral filler. The void
spaces in the compacted aggregate are relatively large.
• Dense gradation occurs when there is a good representation of all
particle sizes and coarse, fine, and mineral fillers.
PARTICLE SIZE
In bituminous construction, it is common practice to designate aggregates
according to particle size. There are three types of designations under this
system, based on two sieve sizes—No. 4 and No. 200.
• Coarse aggregate is all material too large to pass the No. 4 sieve (see
ASTM D 692-88).
Bituminous Mixtures 3-21
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
• Fine aggregate passes the No. 4 sieve but is retained on the No. 200
sieve. In bituminous paving, the fine aggregate is usually a sand, but
small pieces of crushed rock may be used (see ASTM D 1073-88).
• Mineral filler or mineral dust refers to all nonplastic materials which
pass the No. 200 sieve. Most clays are too plastic and are not used.
Generally, crushed rock dust, agricultural mineral filler, lime, or
portland cement may be used as the mineral filler (see ASTM D 546-
88).
SECTION IV. BITUMEN TESTING
The field-identification tests on bitumens identify the material during
expedient conditions or until more detailed tests can be performed. The
identification determines whether the material is an asphalt or a tar and
whether it is a cutback or an emulsion.
Bituminous materials are manufactured to meet specifications established by
the federal government, the AASHTO, and the ASTM. These specifications
define the extreme limits permitted in the manufacture of the material and
assure the user that the material will possess definite characteristics and
fulfill the project requirements. Conforming to specifications tests includes
determining the material’s specific gravity, solubility, analysis by distillation,
and softening point. The equipment for performing these tests is not included
in the asphalt test set and is not normally available to the materials
technician. However, these tests are described for information and, when the
equipment is available, to identify the material beyond field identification, to
furnish information for mix design, or to establish safe-handling procedures.
SPECIFIC-GRAVITY TEST (ASTMS C 127-88 AND C 128-93)
Specific gravity of a bituminous material is defined as the ratio of the weight
of a given volume of the material at 77°F to the weight of an equal volume of
distilled water at the same temperature. The results of a bitumen’s specific-
gravity test are used in the selection of the temperature-volume-weight
correction factor to convert volumes to volume at 77°F. Space is provided on
DD Form 1216 to make this determination (see Figure 3-6). Weigh an empty
pycnometer (specific-gravity bottle), fill it with water, then reweigh. Empty
the water from the bottle and add the bitumen. Weigh the pycnometer and
bitumen. Add water to the same level as the start of the test and weigh the
entire combination. Follow the procedure outlined on the form to compute the
weight of water displaced by the bitumen and the bitumen's apparent specific
gravity. The specific gravity of asphalt cements will usually be in the range of
1.00 to
1.06, with the higher values being characteristic of the harder
materials. The specific gravity of an asphalt has little bearing on quality or
other properties of the asphalt. However, the specific gravity is needed for
other tests and computations. It is needed to adjust the specific gravity of the
water bath in the ductility test. In acceptance and control testing on a job, it
is used as a check on the uniformity of succeeding shipments of asphalt.
3-22 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Figure 3-6. Sample DD Form 1216
Bituminous Mixtures 3-23
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
FLASH-POINT AND FIRE-POINT TESTS
These tests are applicable to asphaltic materials and are of some use in
identifying these materials. Their greatest usefulness, however, is in
determining safe heating temperatures. Material heated above its flash point
presents a real danger, particularly if it is exposed to an open flame.
FLASH POINT AND FIRE POINT BY CLEVELAND OPEN CUP
Perform this test on all petroleum products except fuel oils and those having
open-cup flash points above 175°F.
Equipment
Use the following equipment for this test:
• The flash-point apparatus (see Figure 3-7).
• A knife.
• A frying pan or copper beaker.
• A hot plate.
• A stopwatch.
Figure 3-7. Flash-point apparatus; Cleveland open cup
3-24 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Steps
Perform this test away from any bright light or shield the apparatus, if
necessary. Clean the cup thoroughly before starting. Heat the bituminous
material until it is fluid enough to pour into the cup. Do not move or disturb
the cup and its contents within the last 30° before the expected flash point is
reached. Prevent air movement or drafts across the specimen’s surface.
Perform the following steps:
Step 1. Set up the open-cup apparatus.
Step 2. Adjust the thermometer in a vertical position, 1/4 inch above the
bottom of the cup and about midway between the center and back of the cup.
Step 3. Fill the cup with the heated material until the top of the meniscus is
exactly at the fill line. Let the material cool.
Step 4. Apply heat to the cup so the specimen’s temperature is raised at a rate
of 25° to 30° per minute until a temperature of about 100° below the probable
flash point is reached.
Step 5. Reduce the heat and adjust it so that for the last 50° before the
expected flash point the temperature rise will be not less than 9° and not more
than 11° per minute. Use the stopwatch to regulate this rate. Failure to set
the rate of rise between these limits will result in inaccurate readings.
Step 6. Adjust a test flame to 1/8 to 3/16 inch in diameter, the size of the
comparison bead if one is mounted on the apparatus.
Step 7. Start at least 50° below the expected flash point and pass the test
flame in a straight line across the center of the cup at right angles to the
thermometer and level to the upper edge of the cup. The time for each pass
should be no more than 1 second. Repeat the test-flame pass for each
successive 5°. The flash point is reached when a flash (distinct flicker)
appears at any point on the surface of the material. Read the thermometer at
this time and record the temperature as the flash point.
Step 8. Continue heating at the same rate and applying the test flame at the
same interval until the oil ignites and continues to burn for at least 5 seconds.
Record the temperature at this point as the fire point.
Results
Duplicate tests on the same material by the same operator should not differ by
more than 15°. Results by different laboratories should be considered suspect
if the flash points differ by more than 30° and the fire points differ by more
than 25°.
FLASH POINT BY TAG OPEN CUP (ASTM D 4552-87)
Perform this test on RC- and MC-asphalt cutbacks having a flash point below
200°F.
Bituminous Mixtures 3-25
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Equipment
Use the following equipment for this test:
• A flash-point tester.
• A tag open cup (see Figure 3-8).
• A hot plate.
• A thermometer (20° to 230°F in 1° divisions).
• A torch or test flame.
Figure 3-8. Flash-point apparatus; tag open cup
Steps
Set up the tester in a draft-free and dimly-lit location. Fill the copper water
bath to 1/8 inch below the top of the glass cup (when the top is in place). The
bath may have an overflow to control the water level. Clean and dry the glass
cup and assemble the water bath. Perform the following steps:
Step 1. Place the thermometer vertically midway between the center and the
outer edge of the cup and diametrically across from the guide wire. Set the
bottom of the bulb about 1/4 inch above the bottom of the glass cup.
Step 2. Fill the glass cup with the sample to 5/16 inch below the edge.
Step 3. Place the guide wire in position, touching the rim of the glass cup.
3-26 Bituminous Mixtures
FM 5-472/NAVFAC MO 330/AFJMAN 32-1221(I)
Step 4. Adjust the heat for the sample temperature to rise at 2° ± 1/2° per
minute. Stir thicker material occasionally.
Step 5. Adjust the test flame to not greater than 5/32 inch in diameter, the
size of the comparison bead if one is mounted on the apparatus.
(Some
instruments have a 5/32-inch hole in comparison instead of the bead.)
Step 6. Remove any bubbles that may have formed on the surface before
starting the flame test.
Step 7. Pass the flame at successive 2° intervals; pass the flame across the
sample in a continuous motion, making each pass last 1 second.
Step 8. Record as the flash point the temperature at the time the test-flame
application causes a distinct flash in the interior of the cup.
Step 9. Repeat the test using a fresh sample and starting at least 20° below
the previously determined flash point.
Results
The results of two properly conducted tests by the same operator on the same
asphalt should not differ by more than 18°F. The results of two properly
conducted tests from two different samples of the same asphalt should not
differ by more than 27°F.
PENETRATION TEST (ASTM D 5-86)
The penetration test determines the grade of an asphalt cement. Penetration
is defined as the distance that a standard needle vertically penetrates a
sample of the material under standard conditions of time
(5 seconds),
temperature (77°F), and loading (100 grams). The units of penetration are
hundredths of a centimeter. Other conditions of temperature, load, and time
that are used for special testing are given.
EQUIPMENT
Use the following equipment for this test:
• A hot-water bath.
• A copper beaker or frying pan.
• A stainless-steel box.
• An electric hot plate.
• A sieve pan, 8-inch diameter.
• An asphalt-testing penetrometer (see Figure 3-9, page 3-28).
• A thermometer (66° to 80°F).
• A stopwatch.
STEPS
The described test depends on the water bath being maintained as closely as
possible to the standard temperature of 77°F. Since the penetration of an
asphalt cement varies with temperature, maintain the bath at 77°F. If this is
Bituminous Mixtures 3-27

 

 

 

 

 

 

 

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