Be advised S-1015 dated
12/31/2012 is included in its entirety at the end of this document for
reference only; the official version is available online.
Supplement 1015 details the compaction testing requirements for all
ODOT projects. ODOT technicians and
testing personnel provided by the Contractor must follow the testing procedures
described in S-1015.
When the Contractor provides the compaction testing,
one of two possible supplemental specifications will be included in the
Contract Documents. The two supplemental
specifications, SS-878 and SS-879, are similar, but SS-878 pays for the inspection and testing as a lump sum pay
item, while SS-879 pays for the work by providing incentive pay to the
Contractor.
There is one compaction and inspection table for S-1015, SS-878, and SS-879. Table
1015.9-1 in Section 1015.09 includes
columns for the materials, maximum lot size, and minimum number of tests. The same number and type of inspections and
compaction tests are taken regardless of which specification is used in the
Contract.
This item is used when construction personnel are
limited and the District wants full-time inspection and compaction testing for
the work.
SS-878 pays for the inspection and compaction testing as a
lump sum pay item and covers Items 203, 204, 205, 206, 304, 411, 503, 611, and MSE
wall select granular backfill.
The major aspects of the specification are as follows:
1.
The Contractor is
to supply full-time qualified inspection and compaction testing for all
specified items.
2.
The compaction
tests are performed according to S-1015.
3.
The documentation
is performed on department forms.
4.
The documentation
is presented to the Engineer daily and a summary report is required every 2
weeks.
5.
There are
qualifications requirements for the inspection and compaction personnel.
6.
The Department
will perform QA compaction tests.
7.
There is a lump
sum payment for this work.
The major aspects of the specification are as detailed
below:
1.
Several of the
sections in this specification refer to SS-878, because they are basically the same work with the
payment mechanism being different.
2.
The Contractor
supplies full-time qualified inspection and compaction testing for Items 203 and 204.
3.
The compaction
tests are performed according to S-1015.
4.
The documentation
is performed on department forms.
5.
There are
qualification requirements for the inspection and compaction personnel.
6.
The Department
will perform QA compaction tests.
This supplemental specification is very similar to SS-878, except there is a pay adjustment ± 4 percent to the
amount bid for Items 203 and 204. This specification allows for more Contractor
responsibility for the work with an appropriate incentive. It also allows the Department to reduce the
amount of full-time inspection of the work.
Most of the tables, forms,
graphs, curves, and tests in this section are in English and Metric units. The units are labeled with the English units
first and the metric units in parenthesis (i.e., English [metric]).
Weight measurements should be
measured to the nearest 0.01 of a pound or kilogram. All calculations are normally recorded to the
nearest 0.1 or 4 significant digits.
Normally the final compaction results are recorded to the nearest
percentage of compaction and acceptance is based on rounding. The rounding of 97.6 percent compaction is
rounded up to 98 percent compaction, while 97.5 is rounded down to 97 percent
compaction. The rounding of other
calculations and measurements are done in a similar manner.
The Contractor constructs the
embankment. As the representatives of
the Department, Inspectors and Engineers observe the work to ensure compliance
with the specifications. As the Department inspects the work, instructions are
given to the Contractor, such as the material is too dry, too wet, or does not
have enough stability or density.
What happens when an
embankment fails and we determine that one of the following has occurred?
1. The instructions to the Contractor were in error.
2. Compaction tests were performed incorrectly.
3. Compaction forms were incomplete.
4. No inspection or part-time inspection occurred during
the construction.
All of the above reasons are
arguments that are issues during a claim.
Valid or not, these are reasons that will be debated when responsibility
is discussed. Considerable financial
loss to the Department could result during these negotiations or in court
because of any one of the above reasons.
Our goal with this section is
to minimize the Department liability in the above claim situations.
Compaction testing is an
important evaluation tool that measures the quality of the earthwork
construction work. Therefore, this
entire section is dedicated to obtaining correct and accurate results.
In order to understand
compaction testing, the project personnel must first understand the
moisture-density relationship and some of the variables associated with this
relationship.
A relationship exists between
the density of a soil and the moisture content of a soil as the moisture
content is varied while the compactive effort remains constant. A standard force is used in the test that
closely approximates the densities that can be readily obtained in the field
with footed drum rollers and other types of common compaction equipment. The greatest dry density obtained in the test
is termed, “maximum dry density,” and the corresponding moisture content is
termed, “optimum moisture content.” This moisture-density relationship is shown
in Figure
1015.01.A.
Figure
1015.01.A - Typical Moisture-Density Curve
The test used by the
Department to determine the moisture-density relations of soil is AASHTO T-99, Method C, called the Standard Proctor test. The basic principle involved in the
moisture-density relationship is an important tool when evaluating a soil.
For a given force of
compaction and given moisture content, a soil will have a corresponding
density. Additionally, there is a
particular moisture content for each soil at which a given compaction
requirement can be obtained with less compaction effort than at any other
moisture content. This moisture content
is the optimum moisture content.
Structural properties of a
soil vary with moisture content and density.
For example, a clay soil at a low density will have very high
load-supporting strength when dry, but when it is saturated at this same
density, it will have a very low load-supporting strength. Hence, when the structural properties of the
soil are being determined, its moisture content and density must be defined and
controlled to permit accurate evaluation of the soil in that particular
condition.
Refer to Figure 1015.01.A
to understand the influence of moisture on the compaction of soils. At point 3, the soil is compacted at a
moisture content where the compactive effort cannot overcome the friction or
resistance of the soil to achieve a maximum dry density. As the water content increases, the particles
develop larger and larger water films around them, which tend to lubricate the
particles and make them easier to move about and reorient into a denser
configuration.
As the moisture content is
increased, we eventually reach point 1, where the density does not increase any
further with water content. At point 1,
the soil has just enough moisture to overcome most of the friction and not too
much to have excess pore pressure to displace the soil.
As the moisture is increased
from point 1 to 2, the density decreases as the water starts to displace and
replace soil particles because of the excess pore pressure.
This section outlines procedures
to determine the optimum moisture content, maximum wet density, and maximum dry
density of a soil, shale, or granular materials. This procedure is not normally performed in
the field. It is generally only needed
to determine the optimum moisture content for Test Section Method A.
The procedures outlined in
this section follow AASHTO T-99, Method C with some
minor modifications.
The equipment needed to make
a moisture-density curve is as follows:
1.
Proctor mold.
a.
Cylindrical brass
or cadmium-plated steel mold, approximately 4 inches (102 mm) in diameter,
4-1/2 inches (114 mm) in height, and has a capacity of 1/30 ft3
(9.43 × 10-4 m3).
b.
The cylinder is
mounted on a removable base plate and fitted with a detachable collar
approximately 2-1/2 inches (63 mm) in height.
2.
Proctor hammer.
a.
Brass or
cadmium-plated steel sleeve rammer which has:
i.
A striking face 2
inches (50 mm) in diameter.
ii.
A weight of 5.5
lbs (2.5 kg).
iii.
Equipped to
control the height of drop to 12 inches (305 mm).
3.
Steel
straightedge 12 inches (305 mm) long.
4.
Scale of 25 lb (12 kg) capacity sensitive to 0.01 lbs (1 gram).
5.
A 3/4-inch (19
mm) sieve.
6.
Oil or gas stove
or portable oven unless dried by other methods.
7.
Baking pans, approximately
12 inches × 8-1/2 inches × 2-1/2 inches (300 mm × 200 mm × 63 mm).
8.
Masonry trowel
and putty knife.
9.
If the test is
performed in the field, use a large concrete block or piece of concrete beam.
a.
Minimum size is a
12-inch × 6-inch (300 mm × 150 mm) cinder block.
b.
Or a 4-inch ×
12-inch (100 mm × 305 mm) solid concrete block.
c.
Do not use wood
or asphalt.
Use the form CA-EW-4 (shown in Figure 1015.01.B) to
record test data as obtained by the procedure outlined in this section. This form shows an example of recorded test
data. Each column is lettered and used
throughout this section to facilitate referring to the explanation.
1.
Secure a
representative sample of soil of about 40 lbs (20 kg).
2.
Pass the sample
through a 3/4-inch (19 mm) sieve.
3.
Wet or dry the
sample.
a.
Change the
moisture content to 4 to 6 percent below optimum.
b.
See 1015.01.F,
Estimating Optimum Moisture Content, in this section for more information.
4.
Make a Proctor.
a.
Make a specimen
by compacting the prepared soil in the Proctor mold.
i.
Make three equal
layers to give a total compacted depth of about 5 inches (130 mm).
b.
Compact each
layer by applying 25 uniformly distributed drops from the 5.5 lb. (2.5 kg)
rammer dropping from a height of 12 inches (305 mm) above the elevation of the
soil.
c.
See Figure 1015.01.D for
recommended loose and compacted soil lifts.
i.
Loose lifts will
change depending on the consistency of the soil.
d.
Ensure that the
cylinder is resting on a uniformly rigid foundation during the compaction.
i.
Use a large
concrete block or piece of concrete beam.
ii.
The minimum size
is a 12-inch × 6-inch (300 × 150 mm) cinder block.
iii.
Or a 4-inch ×
12-inch (100 × 305 mm) solid concrete block.
iv.
Do not use wood
or asphalt.
5.
Remove the
extension collar.
a.
The soil should
be less than 1/2 inch (13 mm) above the mold.
b.
If the soil is
lower than the top of the mold, repeat the test.
c.
Carefully trim
the compacted soil even with the top of the mold using the straightedge.
d.
Add fine material
to fill any voids if necessary.
i.
Use the fines
from the tested soil.
6.
Weigh the
cylinder and sample. Input this
information in Column A
a.
Calculate the
density of the specimen by subtracting the weight of the mold from the weight
of the specimen and mold, and multiply the difference by 30 for English units
and 1,060 for metric units.
i.
Column A – 9.81
lbs = Column B
13.34 - 9.81 = 3.53
9.81 is the weight of the mold
ii.
Column B × 30 =
Column C
3.53 × 30 = 105.9
iii.
Column C is the
wet density of the Proctor soil.
7.
Remove the
material from the mold and slice vertically through the center.
a.
Take a representative
sample of the material from one of the cut faces and determine the moisture
content by a method outlined in Section 1015.02.H, Alternate Tests for
Moisture.
b.
If the only
available scales are those included in the compaction control kit, a 1 lb (0.5 kg) sample is required for the moisture
determination. However, if a more
sensitive scale is available, use a 0.22 lb (100
gram) sample. The smaller sample will
dry faster.
i.
The scales need
to be leveled with a carpenter’s level.
Put the scale on a piece of flat plywood then level the board. You may elect to level the weighting plate.
ii.
The older scales
must also be balanced once it is leveled.
The weighting mechanism should float between the top and bottom
bar. If it does not, sand or pebbles can
be added to the lever arm to make it balance.
c.
Calculate the dry
weight and the moisture content as follows:
i.
Column D…Weight
of the dish and the wet soil. 96.2
ii.
Column E…. Weight
of the dish and soil after drying. 93.4
iii.
Column F…Column D
- E = Weight of Water 96.2 - 93.4 = 2.8
iv.
Column H…Column E
- G= Dry Soil Weight 93.4
– 40.0 = 53.4
v.
ColumnI…F/H × 100 = Percent Moisture
Water Content = Weight of Water /Dry Weight (2.8/53.4)
× 100 = 5.2%
vi.
Column J…C/(1+ I)
= Dry Weight of the Soil
Dry Weight =Wet Weight/ (1 + Wc )
In the Example: WD=
105.9/(1+0.052) = 100.5
8.
Thoroughly break
up the remainder of the material until inspection shows that it will pass a
3/4-inch (19 mm) sieve. It is not
necessary to pass all of the material through the sieve.
9.
Add water in
sufficient amount to increase the moisture content of the soil sample by 2 or 3
percent, and repeat the procedure outlined in D through H.
10. Repeat D through H, each time adding water until you
obtain at least 4 readings for the wet weight, dry weight, and moisture
content.
a.
Continue the
process until a minimum of two points are plotted on the wet and dry side of
the dry weight curve and there is a decrease in the wet weight.
11. Use Figure 1015.01.C) as an example and plot test data as follows:
a.
Plot wet weight,
Column C, versus moisture content, Column I, of the successive tests on linear
graph paper.
i.
Draw a smooth
curve between the successive points.
ii.
The peak of this
curve is the maximum wet weight of the material being tested.
iii.
This maximum
weight is not used for compaction acceptance.
b.
Plot dry density,
Column J, versus moisture content, Column I, of the successive tests on linear
graph paper.
i.
Draw a smooth
curve between the successive points.
ii.
The peak of this
curve is the maximum dry density of the soil.
iii.
The moisture
content at this point is the optimum moisture content.
iv.
This curve can be
used for compaction acceptance.
Figure 1015.01.C (1015.01.C-M) shows curves
plotted from the test data in Figure 1015.01.B.
Figure
1015.01.B – Moisture-Density Calculation Form
Figure
1015.01.C – Moisture-Density Curve Plot
Figure
1015.01.D - Loose and Compacted Lifts for the Proctor Test
The Ohio Typical Density
Curves are a set of soil curves originally developed in the 1930’s and 1940’s
to represent all the soils in Ohio. They
were developed in the laboratory using the standard Proctor test. They started with an original set of nine
curves that represented over 1,000 samples.
Additional curves were added that represent over 10,000 lab
samples. These curves are plotted in
Figure 1015.01.E. These curves are still used today to represent
all the soils in Ohio. Using these
curves minimizes the need to make moisture-density curves for each type of soil
encountered in the field.
Figure
1015.01.E - Ohio Typical Density Curves
A one-point Proctor test is
used to choose the curve that represents the soil under consideration. The procedure is similar to the AASHTO T 272 test and is detailed in Supplement 1015.06.C.1.
By examining the
moisture-density or the Ohio typical density curves, one can gain general
information on the load-carrying capacity and other information about the soil
properties.
The optimum moisture content
and maximum dry density of the moisture-density relationship are comparative
factors. A high maximum dry density
ranges from 125 to 140 lbs/ft3 (2,000 to 2,250 kg/m3) dry
density. A low maximum dry density
ranges from 100 to 85 lbs/ft3 (1,600 to 1,350 kg/m3) dry
density. A low optimum moisture content
coincides with a high maximum dry density and will be on the order of 7
percent. A high optimum moisture content
coincides with a low maximum dry density and may be on the order of 25 percent.
The maximum dry density of a
soil gives approximate information on its gradation and soil type. The approximate range of the maximum dry
density for particular soils are as follows:
Soil Type |
Typical Maximum Dry
Density |
A-1 & A-2 |
120 to 135 (1922 to 2163)
Granular Soils |
A-2 |
120 to 130 (1922 to 2082)
Granular Soils |
A-3 |
110-to 120 (1762 to 1922)
Granular Soils |
A-4 |
105 to 120 (1682 to 1922)
Silty Soils |
A-6 & A-7 |
90 to 110 (1442 to 1762)
Clayey Soils |
The optimum moisture content
gives approximate information on the clay and silt content of the soil. The shape of the moisture-density curve varies
from a sharply peaked parabolic curve to a flat one or to one sloping
irregularly downward as the moisture content increases. This shape gives
additional valuable information showing the influence of moisture on the
load-supporting value of the soil. For
example, a flat moisture-density curve indicates a soil that will have about
the same load-supporting strength over a wide range in moisture contents, while
a moisture-density curve with a sharp peak indicates a soil that is sensitive
to changes in moisture content.
To truly understand the
moisture and density relationship as it relates to soil compaction, the project
personnel should understand what items affect this relationship. This section briefly addresses these issues.
This moisture-density
relationship is affected by, but not limited to, the following conditions:
1. A change in the laboratory compactive effort or a
field compactive effort that is different from the laboratory testing
compactive effort.
2. A temperature of the compacted soil that is near or
below freezing temperature.
3. Coarse aggregate that is added or subtracted from the
soil.
The AASHTO T 99 Proctor test, used to make the Department’s
moisture-density curve, was originally made to simulate field compaction
conditions. It uses a standard
compactive effort that allows us to evaluate and compare the compaction and
densities of different soils. What
happens to this moisture-density relationship as you increase or decrease this
compactive effort?
In Figure 1015.01.F,
the compactive effort may be increased or decreased to change the maximum
density as much as 10 to 15 lbs/ft3 (160 to 240 kg/m3). As the compactive effort increases, the curve
shifts to the left and up along the same line of optimum. If the compactive effort is lowered, the
compaction curve shifts to the right and down.
Figure
1015.01.F - Changing the Compactive Effort
If a soil is compacted at low
temperatures, the maximum density cannot be achieved in the field. The specifications do not allow soil to be
compacted that is frozen. Figure 1015.01.G shows why this is the case. The maximum density can change as much as 10
lbs/ft3 (160 kg/m3) for soils compacted at temperature
differences of 40 ºF (20 ºC). However,
there may not be any difference in maximum density. Temperatures affect some soils but not
others. There is not a formula that
takes this temperature difference into consideration.
Figure
1015.01.G - Temperature Effects on the M-D Curve
Compaction procedures must be
altered to check for this difference.
Use the following procedure when the Contractor is compacting the soil
at temperatures lower than 45º F (7º C) or when the site conditions
warrant:
1. Take the normal Proctor test during the compaction
testing. Choose the curve associated
with this compaction test.
2. Take enough soil from the same hole to make another
Proctor later. After the soil is warmed
to approximately 70 ºF (21 ºC) make an additional Proctor. Pick an additional curve using the wet weight
of the second Proctor and moisture content from a drying method.
3. Compare the two results and use the higher curve if
there is a difference. Use this
procedure at any time the material is suspect in the field.
The moisture-density
relationship is very good for soils passing the 3/4-inch (19 mm) sieve as it
relates to the field compaction of soils.
There are problems when this relationship is extrapolated to soils
larger than the 3/4-inch (19 mm) sieve material or for granular soils. Corrections must be made to account for these
materials. In certain circumstances,
field densities do not correspond to the laboratory results. These will be pointed out in later sections.
Figure 1015.01.H details a plot of adding
or subtracting coarse aggregate to a soil and the resulting change in the
moisture-density curves.
Figure
1015.01.H - Coarse Aggregate Effects on Soil M-D Curve
As you add gravel or 3/4-inch
(19 mm) material to the soil, the optimum moisture content shifts to the left
and the maximum density increases. The
average increase in density is approximately 1 percent per 10 percent of
material retained on the 3/4-inch (19 mm) sieve. This effect is taken care of on the CA-EW-6 Compaction Form and is fully
explained in Section 1015.03
of this manual.
If you sieve the material
through the 3/4-inch sieve, remove 20 percent coarse aggregate, and do not
consider this, you could easily be one or two curves lower than intended.
Use the correction on the CA-EW-6 Compaction Form where more
than 10 percent of the material is retained on the 3/4-inch (19 mm) sieve. This correction usually increases the maximum
dry density and makes an optimum moisture content correction.
The accuracy of all
compaction testing is important; however, the importance of making temperature
and coarse aggregate corrections in compaction testing are less obvious to the
project personnel. Without these
corrections, the compaction testing could easily be off by more than 2 lbs/ft3
(32 kg/m3) without the project personnel being aware of a problem.
If the compaction testing is
off by 2 lbs/ft3 (32 kg/m3), or approximately one Ohio
Typical Density Curve, this may result in a loss of 15 percent of the soil
strength. If the testing is off by two
curves, the potential loss could be 30 percent, and so on. The strength may not be apparent in
construction, but in the long-term, it may have devastating effects on the
performance of the embankment.
All cohesive soils are
compacted at water contents less than the plastic limit of the material. For A-7-6 soils, the optimum moisture content
is around the plastic limit minus 3. For
A-4 and A-6 soils, the optimum is around the plastic limit minus 5. The optimum moisture content of granular
materials ranges between 5 and 10 and for non-plastic silts is around 11.
You can obtain an estimate of
the material’s consistency by using the above information and looking at the
soil’s water content from the soil borings before the work begins. Keep in mind, the water content on the soil
borings is the water content at the time the borings were drilled. They should be considered an estimate of the
present field conditions.
You can approximate the
optimum moisture content of a material by the feel of the material in the field
using one of the following methods.
1.
Take a sample of
the material in question in your hand.
2.
Squeeze the
material together and let go.
3.
4.
Consult the
following table:
If the material… |
Then material is… |
Falls apart in small pieces |
Dry of optimum |
Stays together |
At or above optimum |
Breaks into two or three large pieces |
At optimum |
Stays together and there is excess water on hands |
Above optimum |
5.
Roll the material
into a 1-inch ball.
6.
Place it between
your thumb and index finger and squeeze the material.
7.
Consult the
following table:
If the material… |
Then material is… |
Ball cannot be formed |
Below optimum |
Becomes oval |
Above optimum |
Breaks apart into uniform pieces (Some clays will have larger pieces than silts) |
At optimum |
8.
Spit on the
material.
9.
Consult the
following table:
If the saliva… |
Then material is… |
Beads up |
Above optimum |
Slowly sinks in |
At optimum |
Use these methods as
estimates; they do not replace compaction testing. These estimates are different for each type
of soil (clay, silt, granular).
Proper compaction at the
proper moisture is the most effective and most economical way to improve the
stability of soils. Satisfactory
performance of pavement and embankment depends on the good compaction of the
embankment and subgrade materials.
Careful control is necessary to ensure compliance with the specification
compaction requirements for embankments and subgrades.
The density test is the
principal means by which the Engineer determines whether or not the specified
compaction requirements have been met.
The number of tests to be made for a given quantity of embankment
material placed is set by Supplement 1015.09.
The Engineer has broad powers to increase or decrease this testing
depending on the field conditions. The
Engineer may use his or her judgment to make tests at locations where the
information is most needed for proper control.
For example, consider an area
of embankment under construction, where the soil and moisture conditions are
uniform and ideal for good compaction, and where previous compaction tests have
shown that the specification requirements are
consistently met under the same number of roller passes. As long as inspections show that the uniform
conditions of soil, moisture, lift thickness, and roller pass continue for this
area, only occasional check tests for compaction are required.
Where relatively few tests
are made because materials and conditions are uniform, document this by
describing conditions on the Compaction Forms or other appropriate project
records. Avoiding a large number of
tests in areas of uniform condition, where specified compaction is consistently
obtained, allow the project personnel to concentrate their effort on other
areas of the project where conditions are less uniform or suspect.
Tests must be made in areas
where inspection indicates that the material is questionable, even if specified
compaction is obtained. Evidences of
questionable compaction, which can be determined by inspection, include the
following:
1. Low number of roller passes to obtain compaction.
2. Excessive deflection under heavy construction
equipment.
3. The use of lightweight rollers.
4. Very wet or dry soil.
5. Areas compacted without full-time inspection.
6. Inconsistent materials, such as shale and rock
mixtures, or recycled concrete mixed with soil.
The observation that a footed
drum roller will “walk out” or “ride high” on a layer of hard, dry soil is not
evidence of satisfactory compaction.
This soil may be stable when dry, but weak when wet.
Areas where compaction or
moisture does not meet specification requirements must be corrected before the
next lift of embankment is placed.
The Engineer must give
specific directions to the Inspectors.
These directions must cover the Inspector’s responsibility and authority
given to them by the Engineer. This
ensures that timely decisions are made in the field and that full compliance
with the contract requirements is obtained on the project.
Control of compaction
includes making moisture and density determinations for establishing whether
the compaction meets the requirements prescribed in the specifications.
A sufficient number of tests
must be made to ensure that construction complies with the specifications. The Nuclear Gauge Method is the only method
used for compaction testing. The
sand-cone, rubber-balloon, and cylinder density tests have been eliminated.
Regardless of the method
chosen, a one-point Proctor test is used to identify the curve that represents
the soil in question for each compaction
test, except for materials requiring a test section.
1. Equipment listed in Section 1015.04.
2. A 3-inch (75 mm) or 4-inch (100 mm) post-hole auger.
3. A container with a 4-1/2-inch (114 mm) hole cut in the
bottom.
4. Troxler 3440 Nuclear Gauge.
5. 25 to 50 lbs (12 to 23 kg) of dry, uniform, natural
sand passing the No. 10 (2 mm) sieve.
6. Form CA-EW-5, Nuclear Gauge Compaction
Form, and Form CA-EW-6, Nuclear Gauge Compaction
with an Aggregate Correction.
Select a location for the
density test that is representative of a rolled area of the embankment layer
being constructed. If loose, uncompacted
material, similar to what results from sheepsfoot rolling, exists on the
surface, remove the loose material to expose the compacted material underneath. Carefully level the test area by any convenient
means, such as a dozer, grader, hand shovel, straightedge, etc.
The Department uses nuclear
equipment manufactured by Troxler Laboratories. Presently the Department uses the 3440 series
gauges. The operator should have a
Manual of Operation for the gauge.
There is no radiological
danger for the operation of a nuclear gauge so long as the correct operating
and safety rules are followed. Each
operator is issued a specific set of instructions governing safety when the
gauge is assigned to him or her. For
more information about the safety requirements see the following link to the
Nuclear Labs website:
www.dot.state.oh.us/Divisions/ConstructionMgt/Materials/Pages/Radiation-Safety.aspx
In addition, contact the
Nuclear Lab at (614) 275-1375 for more information.
For nuclear measurement of
density, gamma rays emitted into the soil from a gamma source are scattered by
the electrons in the soil and lose energy in the process. The number of scattered rays returned and
counted in the gauge depends on the average length of the path of the ray
between the detector and source. The electron
density increases proportionally with the density of the soil and causes
greater scattering and energy loss.
Therefore, the chances that scattered gamma rays returning to the
detector with sufficient energy to be counted become smaller with increased
soil density, and the count rate drops.
In common soil types, a low gamma ray count indicates a high density,
and a high count indicates a low density.
For nuclear measurements of
moisture, the neutron energy absorption technique measures the moisture content
of rock or soil materials. The nuclear
method for measuring the moisture content of soil and rock materials is based
on the principle of measuring the slowing of neutrons emitted into the soil
from a fast-neutron source. The energy
loss is much greater in neutron collisions with atoms of low atomic weight and
is directly proportional to the number of atoms present in the soil. The effect of such a collision changes a fast
neutron to a slow neutron. Hydrogen,
which is the principal element of low atomic weight found in soils, is
contained largely in the molecules of water in an inorganic soil. The number of slow neutrons detected by the
gauge, after an emission of fast neutrons from a radioactive source, is counted
electronically in the gauge. The count
obtained by the gauge is proportional to the amount of water in the soil or
rock.
Density and moisture
determinations can be made in any of the following two positions relative to
the material being tested:
1. Backscatter - Source and detector in the gauge are
resting on the surface of the material being tested.
2. Direct Transmission - Source in the rod is extended
below the gauge into the material being tested, and the detector in the gauge
is on the surface of the material being tested.
Figure 1015.02.A
- Nuclear Gauge Direct and Backscatter Positions
Use Form CA-EW-5 or CA-EW-6 for
moisture-density testing when using a nuclear gauge. The following is a summary of the gauge
operations when testing soils. Consult
the detailed explanation in the owner's manual of procedures. The gauge is self-driven throughout the
process. The operator pushes a button
and the gauge asks a question or gives an answer.
1. Determine the standard count.
a. Perform at the beginning of each day the gauge is used
or when the test location environment changes.
b. Put the gauge on the standard block with the handle
opposite the metal plate. See Figure
1015.02.B.
Figure
1015.02.B - Nuclear Gauge on the Standard Block
c. Make sure the standard block is resting on material
which weighs more than 100 lbs/ft³ (1600 kg/m3).
d. Press the "ON" button on the gauge panel (see
Figure 1015.02.C).
i.
Wait
approximately 4 minutes for the gauge to warm-up.
ii.
The gauge may
already be on prior to placing it on the block.
iii.
The gauge will
beep when ready.
Figure 1015.02.C
- Nuclear Gauge Keypad
iv.
Readout:
1. Depth: safe position.
2. Time: 1 minute (possibly a longer duration).
3. Battery: volts.
e. Press the standard button.
i.
Readout:
1. Do you want to take a new standard?
2. Press "YES."
3. Is the gauge in the safe position?
4. Press "YES."
ii.
Readout:
1. Taking a standard count.
2. Takes 240 seconds.
3. Gauge will beep when complete.
iii.
Readout when
standard count is complete:
1. MS XXXX X.X%P
2. DS XXXX X.X%P
3. P-Pass, F-Fail
4. If reading is within 1 percent for density or 2
percent for moisture, the standard passed.
f. Record standard count on lines 4 and 7 on the CA-EW-5 and lines 1 and 2 on the CA-EW-6.
g. Do you want to accept the new standard?
i.
Press
"YES" if acceptable.
ii.
Readout:
1. Ready.
2. Depth.
3. Volts.
4. Ready to take the readings.
2. Taking Nuclear Gauge Readings.
a. Clear away all loose material or dried crust.
i.
Obtain a level
area with sufficient size to accommodate the gauge.
ii.
Use the scraper
plate to help smooth out the surface.
iii.
See Figure
1015.02.D.
Figure
1015.02.D - Scraper Plate and Use
b. Use the native fines or fine sand to fill the voids to
finish smoothing out the surface.
i.
The maximum void
beneath the gauge should not exceed 1/8 inch (3 mm).
c. Make a hole perpendicular to the prepared surface by
using the pin (drill rod) provided by the manufacturer.
i.
Drive 2 inches
(50 mm) further than the depth of the reading.
d. Mark the outside of the scraper plate.
e. Remove the scraper plate and position the nuclear
gauge on the prepared location.
i.
Raise the gauge
up on one side and extend the rod out about 2 inches (50 mm).
ii.
Place the rod
over the hole and extend the rod the rest of the way.
f. Extend the rod to the required depth. See Figure 1015.02.E.
Figure
1015.02.E - Positions of the Nuclear Gauge
i.
Backscatter
Position is used for:
1. Bases.
2. Granular Materials.
3. Materials requiring a test section.
ii.
8-inch (200 mm)
depth used for embankment.
iii.
12-inch (300 mm)
depth used for subgrade.
iv.
The gauge gives
the depth.
v.
The deepest depth
is the most accurate.
g. Pull the gauge toward the detector end or away from
handle to seat the gauge into position (see Figure 1015.02.A).
i.
Eliminates the
air gap between the source rod and the hole.
h. Press "START/ENTER."
i.
After one minute:
i.
Readout:
1. DD = Dry Density = Line 6= 133.0 lbs/ft3
2. WD = Wet Density = Line 5 =144.4 lbs/ft3
3. % M = % moisture = Line 8 = 8.3%
j.
Record
information on Lines 5, 6, and 8 of the CA-EW-5 Form and on lines 3, 4, and 5
on the CA-EW-6 form.
k. See Figure 1015.02.F.
i.
DD = Dry Density
= Line 6= 133.0 lbs/ft3
ii.
WD = Wet Density
= Line 5 =144.4 lbs/ft3
iii.
% M = % Moisture = Line 8 = 8.3%
Optimum moisture content and
maximum dry density can be determined from the Proctor test results, nuclear
gauge results, and the Ohio Typical Density Curves as described in Section
1015.01.C and 1015.01.D. Use the Plotted
Ohio Typical Density Curves for compaction testing, which are in S-1015.
Once the wet density and
percent moisture is obtained from the Proctor test, it can be used to find the
curve that represents the soil being tested.
Use nuclear method or drying method to determine percent moisture in
lieu of the penetration resistance method; do not use the penetration
resistance method.
Figure
1015.02.F - Completed CA-EW-5 Compaction Form
1. Secure a representative soil sample of about 10 lbs (5
kg).
a. Use the soil between the end of the probe and the back
of the gauge (see Figure 1015.02.A).
2. Sieve the material through a 3/4-inch (19 mm) sieve.
a. Use Form CA-EW-5 if less than 10 percent of the soil
is retained.
b. Use Form CA-EW-6 if more than 10 percent of the soil
retained.
c. Use a Test Section Method if more than 25 percent is
retained.
3. Thoroughly mix the material passing the 3/4-inch (19
mm) sieve.
4. Make a proctor using Section 1015.01.B.2 of this
manual.
a. Make a Proctor test for every compaction test (a soil
cannot be correctly identified without this test).
b. When weighing the Proctor mold and soil, the scales
must be level and balanced.
i.
The scales need
to be leveled with a carpenter’s level.
Put the scale on a piece of flat plywood and then level the board. You may elect to level the weighting plate.
ii.
The older scales
must be balanced once it is leveled. The
weighting mechanism should float between the top and bottom bar. If it does not, then sand or pebbles can be
added to the lever arm to make it balance.
5. Record and calculate the proctor results on Lines 10
through 13 on the CA-EW-5 and lines 11-14 on the CA-EW-6.
a. Use Figure 1015.02.F.
b. Line 10 (14.01 lbs) – Line 11(9.24 lbs) = Line 12
(4.77 lbs)
c. Line 12 (4.77 lbs) × 30 = Line 13 (143.1 lbs/ft3)
6. Pick the Wet density Curve Using
a. The Proctor wet density.
b. Line 13 = 143.1lbs/ft3
c. Moisture from gauge readings or by another drying
method.
d. Line 8= 8.3%
7. Use the printed Ohio Typical Density or Project Curves
(see Figure 1015.02.G).
a. Draw a horizontal line through the wet density on the
Ohio Typical Density Curves from the Proctor weight on Line 13, on the CA-EW-5,
or Line 14, on the CA-EW-6 Form.
i.
Line 13 = 143.1
lbs/ft3
b. Extend a vertical line from the percent moisture shown
on Line 8 on the CA-EW-5 or Line 5 on the CA-EW-6 Form to intersect the
horizontal line.
i.
Line 8 = 8.3%
Figure
1015.02.G - Example of Using the Ohio Typical Density Curves
c. If the intersection falls on a curve, choose the
curve.
d. If the intersection falls between two curves, choose
the next highest curve.
8. Use the maximum dry weight and optimum moisture data
in the upper right hand corner of Figure 1015.02.G from the curve that is
chosen.
a. In this example, curve “D” is the correct curve.
9. After the curve is selected, record optimum moisture
content on Line 14 and the maximum dry density on Line 15 of Form CA-EW. For
the CA-EW-6, record the optimum moisture content on Line 15 and the maximum dry
density on Line 18.
a. Line 15 = Maximum Dry Density = 134.1 lbs/ft³
b. Line 14 = Optimum Moisture Content = 8.5%
Use Figure 1015.02.F.
1. Use line 16 to calculate the difference in moisture
contents.
a. Line 14 = 8.5 percent - Line 8 (8.3 percent) = - 0.2
percent (below optimum)
2. Use line 17 to calculate compaction.
a. (Line 6/ Line 15) × 100 = (133.0 lbs/ft3/ 134.1
lbs/ft3) × 100 = 99.2 percent.
3. Compare to the allowable in the specifications shown
in Table 203.07-1.
Table
203.07-1 Embankment Compaction Requirements
Maximum Laboratory Dry Weight (lb/ft3 ) |
Minimum Compaction (percent) |
90 to 104.9 |
102 |
105 to 119.9 |
100 |
120 and more |
98 |
a. Since Line 15 = 134.1 lb/ft3
> 120 the minimum required compaction is 98 percent.
b. Line 17 = 99.2 percent > 98 percent
c. The test passes.
4. If density and stability are achieved, then moisture
passed.
a. See Manual of Procedures Section 203.07.
5. Check zero air voids.
a. Use Figure 1015.01.02.H.
b. Use line 6 = 133.0
i.
Get 9.5
c. 9.5 percent > Line 8 = 8.3 percent
d. Good (Line 8 may be a maximum of 1 percent above the
Figure 1015.02.H value).
Can calculate the percentage
by using the formula in Figure 1015.02.H
i.
Where G = 2.67
and D = line 6
ii.
If you are good
with math, then the formula is much easier to use than the graph.
6. The check on the zero air voids is not required by
S-1015, but it is a good check on the nuclear gauge readings. The moisture obtained from the curve or graph
is the maximum moisture that can exist in the soil being tested. If the gauge moisture readings are larger
than the ones obtained from the graph, then an error may exist in the test.
Figure
1015.02.H - Zero Air Voids Curve
This section discusses
moisture controls during construction, details some of the variables in the
moisture controls, and discusses alternate methods used to verify or modify the
moisture readings from the nuclear gauge.
Experience has shown that to
obtain the specification density, the moisture content must be at or near
optimum. Some soils, particularly silty
soils with low plasticity, may meet the moisture (± 3 percent from optimum) and
the compaction requirements, but have unsatisfactory stability.
Some soils compact better and
meet the density and stability requirements at minimum moisture of -3 or more
below optimum. The reason for limiting
the moisture contents for soil embankment this way is to ensure stable
embankments.
The Elasticity and
Deformation of Soils is discussed in Section 203.02 and Moisture Controls are
discussed in Section 203.07.A of this manual.
There is not a numerical
moisture requirement in the specifications.
The Contractor must compact the material at a moisture content to obtain
the density and stability of the material.
Moisture and compaction controls are necessary to secure the quality of
embankments and subgrades that are essential for the long life and performance.
The specifications do not
numerically limit the moisture content of embankment or subgrade soils. Moisture determinations must be made in the
field to pick the required moisture-density curve and to control the Contractor’s
compaction operations. The following
sections deal with various methods of determining moisture contents of soils.
For engineering purposes, the
moisture of soil is expressed in percent of dry weight.
Percent Moisture = |
Weight of water in soil |
× 100 |
Weight of dry soil |
Most of the time, the
moisture of a soil should be obtained by using the nuclear gauge readings. However, there are situations where drying
methods can and should be used. Moisture
content is the most variable reading from the nuclear gauge. There are varieties of chemicals in the soils
that can minimize the moisture content reading reliability. This is particularly true for recycled
materials, such as fly ash, bottom ash, foundry sand, or asphalt.
Use the moisture estimating
principles detailed in Section 203.02 Estimating Optimum
Moisture Content. This section guides
the determination of an alternate moisture measurement.
For each drying method, the
soil to be tested should be a representative sample of at least 1 pound (0.5
kilograms). The soil should be placed in
a small, clean can or jar and covered with a tight lid at the construction site
to prevent evaporation of moisture while moving to the location of the
test. The test should be conducted as
soon as possible after taking the sample.
Location where sample is taken must be noted.
All the moisture tests should
be checked against each other to ensure accuracy of the moisture testing. To record the moisture results, use Figure
1015.01.B, Moisture-Density Calculation Form, and read the appropriate
sections.
This method of determining
moisture content is applicable to all types of soils. The time required to dry the sample depends
on the size and moisture content of the sample and the type of soil.
This method should be used
for any recycled material. This can be
used to apply a moisture correction to the nuclear gauge readings when the
material is uniform. This is
particularly true for fly ash.
1. Two-burner stove.
Either oil stove or a camp stove using white gasoline.
2. “Boss 75” portable oven or equivalent.
a. This oven measures approximately 20 inches (0.5
meters) high, 20 inches (0.5 meters) wide, and 13 inches (0.3 meters) deep.
b. It sets on and is heated by the stove.
3. Several baking pans approximately 12 inches × 8-1/2
inches × 2-1/2 inches (300 mm × 200 mm × 63 mm).
4. Masonry trowel or putty knife.
5. Can of fuel.
The can has tight stoppers and is painted red if used for gasoline.
6. Scale of 25 pound (12 kilogram) capacity sensitive to
0.01 pound (1 gram).
7. Piece of flat glass or pieces of bond paper with
texture similar to the compaction forms.
1. Weigh the pan to the nearest 0.01 pound (1 gram). Record the weight.
2. Place approximately 1 pound (0.5 kilograms) of
representative sample of wet soil in the pan on the scale.
a. Record the combined weight.
3. Break-up all lumps of soil with the putty knife or
trowel and avoid any loss of the sample.
4. Place the pan with the sample in the oven with the
stove on. Stir the soil every 3 to 5
minutes.
5. After the soil has changed to a lighter color and
appears to be dry, remove the soil sample from the oven and test to determine
if it is completely dry by using one of the following methods:
a. Lay a piece of bond paper approximately 2 inches × 3
inches (50 mm × 75 mm) on the sample.
i.
If the paper
curls immediately when laid on the sample, the soil contains moisture.
ii.
The paper used
for this test must be bond of hard surface texture like the paper used for the
compaction forms.
b. Hold a piece of clean glass or a mirror in a
horizontal position about 1 inch (25 mm) above the soil sample.
i.
If the glass
steams up, this is an indication of further moisture in the sample.
c. Keep the glass away from the heat of the stove or
direct rays of hot sun prior to the test since this test depends upon condensation
of moisture in the hot air onto the cooler glass.
6. If the test indicates further moisture in the sample,
stir the sample and continue drying.
a. Test the soil every 3 to 5 minutes until the test
indicates the soil is dry.
7. Weigh the dried sample and pan to the nearest 0.01
pound (1 gram). Record this weight.
8. Subtract the weight of the pan from the weight of the
pan and the dry sample to obtain the weight of the dried sample.
9. Subtract the weight of the dried sample from the
weight of the wet sample. This is the
weight of water in the original sample.
10. Divide the weight of the water by the weight of the
dried sample. Multiply this result by
100. This gives the percentage of
moisture in the sample. The equation is:
Percent Moisture = |
Weight of wet soil – Weight of dry soil |
× 100 |
Weight of dry soil |
This method is quick, simple,
and obtains accurate results for granular material. This method should not be used for fine-grained
soils (silts or clays) because the high temperatures may burn away the organic
material if it happens to be present.
This method can be used for fine-grained soils where limited accuracy is
satisfactory and approximate moisture results are acceptable.
This method should not be
used for any recycled material. It has
been found to give lower moisture contents than is really in the material. This is particularly true for fly ash.
1. Scale of 25 lbs (12 kg) capacity sensitive of 0.01 lbs
(1 gram).
2. Several baking pans approximately 12 inches × 8-1/2
inches × 2-1/2 inches (300 mm × 200 mm × 63 mm).
3. Putty knife or other device for breaking up and
stirring the soil.
4. Two-burner stove burning white gasoline.
5. Piece of flat glass or pieces of hard surface bond
paper with texture similar to the compaction forms.
Follow steps outlined in
Section 1015.02.H.3, Oven-Drying Method, Steps A thru L, except place the pan
directly over the burner instead of in the oven.
The following cautions should
be taken to avoid introducing errors into the test.
1. Avoid overheating the soil.
a. Use two pans, one inside the other, to avoid hot spots
that may occur when a single pan is used.
2. Avoid baking the soil.
a. Baking can be prevented by testing the material with a
paper or glass test at sufficiently close intervals, so that further heating
can be discontinued after all the moisture has been evaporated.
3. Ensure that no soil is lost during the test.
This method is quick and
simple. The alcohol burns at a low
enough temperature 286 ºF to 320 ºF (140 ºC to 160 ºC) so that it can be used
with accuracy for most soil types.
This method should be done
outside or in a well-ventilated area.
1. Scale of 25 lb (12 kg)
capacity sensitive of 0.01 lb (1 gram).
2. 12 × 8.5 × 2.5 inches (300 × 200 × 63 mm) baking pan.
3. Pan or can with perforated bottom and filter paper to
fit bottom.
a. A 10 oz (300 mL) round
sample can is suitable for this purpose.
4. Glass stirring rod.
5. Supply of alcohol in tightly sealed can.
1. Weigh perforated pan or can with filter paper in the
bottom. Record weight.
2. Place sample of wet soil in perforated pan or can;
weigh and record weight.
3. Place perforated pan or can in larger pan and stir
alcohol into the soil sample with a glass rod until the mixture has the
consistency of a thin mud or slurry.
a. When stirring, do not disturb the filter paper on the
bottom.
b. Clean the rod.
4. Ignite the alcohol in the other pan and in the sample
and burn off all alcohol.
5. Repeat the process three times or until successive weighings indicate no reduction in weight after each time
burning.
6. After final burning, weigh perforated can or pan and
dry soil, and record weight.
7. The weight of dry soil equals the weight minus weight
of perforated pan or can and filter.
8. Calculate moisture content as shown in Section J
though L of Section 1015.02.H.3.
This is a quick and simple
method of drying. However, the gasoline
burns at such a high temperature that it should be used only to dry granular
materials. This method should only be
conducted outside.
This method of drying is
similar to the alcohol-drying method with the exception that the perforated pan
and filter are not used. The gasoline
can be mixed with the sample in the baking pan and burned in the pan. Except for this, the test is run exactly the
same as the alcohol-burning method, described in Section 1015.02.H.5.
As detailed in Section 1015.01.E.3
Coarse Aggregate Problem, the moisture-density relationship is very good for
soils passing the 3/4-inch (19 mm) sieve as it relates to the field compaction
of soils. There are problems when this
relationship is extrapolated to soils larger than the 3/4-inch (19 mm) sieve
material or for granular soils. Corrections
must be made to account for these materials.
In certain circumstances, field densities do not correspond to the
laboratory results.
Figure 1015.03.A details a
plot of adding or subtracting coarse aggregate to a soil and the resulting
change in the moisture-density curves.
As you add gravel or add 3/4
inch (19 mm) material to the soil, the optimum moisture content shifts to the
left and the maximum dry density increases.
The average increase in density is approximately about 1 percent per 10
percent of material retained on the 3/4-inch (19 mm) sieve.
Figure
1015.03.A - Coarse Aggregate Effects
If you sieve the material through
the 3/4-inch-sieve, remove 20 percent coarse aggregate, and do not consider
this, you could easily be one or two curves lower than intended.
This correction usually
increases the maximum dry density and reduces the optimum moisture
content. This effect is taken care of on
the Compaction Form CA-EW-6.
Use the correction on the CA-EW-6 Compaction Form where more
than 10 percent but less than 25 percent of the material is retained on the
3/4-inch (19 mm) sieve. See Figure
1015.03.B, Aggregate Correction Method.
Figure
1015.03.B - Aggregate Correction Method
Caution: Sand which is almost
pure may have between 10 to 25 percent retained on the 3/4 inch-sieve. A test section method would be used in this
case. This method is to be used with
Fine Grained Materials with significant granular material retained.
A completed form is detailed
in Figure 1015.03.C. The general
sections of this form are as follows:
Figure
1015.03.C - Completed CA-EW-6 Compaction Form
(Pictures
added for clarity)
Lines
1 thru 5 are explained in Section 1015.02.D.
This
section is a straightforward calculation of the stone retained on the 3/4-inch
sieve. Calculate through lines 6 through
10.
The
percentage on line 10 is represented by the following equation:
Percent of Stone in Sample = |
Weight of stone retained |
× 100 |
Weight of total soil sample |
See
Section 1015.02.F,
Section D, and 1015.01.B.2
for an explanation of lines 11 thru 14.
See
Section 1015.02.F
for an explanation of lines 15 through 18.
Line
19 is explained in Section 1015.02.G.
This
section uses Figure 1015.03.D, Aggregate Correction Graph A, and Figure
1015.03.E, Moisture Correction with an Aggregate Correction, to find a new
maximum dry density and optimum moisture.
The
Nuclear Gauge Test is similar to Section 1015.02 with the exceptions being the
calculation of the percent retained on the 3/4-inch sieve on line 10 in Section
II and Section VI is new.
This section details Figure 1015.03.D,
Aggregate Correction Graph A.
The instructions are on the
graph.
1. The inputs needed are:
a. The specific gravity of the stone retained on the
3/4-inch sieve.
i.
The typical
values are listed on the graph.
b. The maximum density found on line 18: 109.6 lbs/ft3.
c. The percent retained on the 3/4-inch sieve on line 10:
20 percent.
2. Draw a line between the specific gravity and the value
on line 18.
3. Input line 10 value on the bottom of the graph and
draw a vertical to the line drawn previously.
4. Continue the line to the left on a right angle to the
corrected maximum dry density.
5. Input this value found on line 20 on the CA-EW-6.
This is the corrected maximum
dry density: 116.5 lbs/ft3.
Figure
1015.03.D - Aggregate Correction Graph A
New optimum moisture is found
by inputting the new maximum dry density into the maximum density values in the
upper right hand corner on Figure 1015.03.E.
Figure
1015.03.E - Moisture Correction for an Aggregate Correction
For example, the maximum dry
density on line 20 is 116.5 lbs/ft3.
This value is between curve K (117) and L (114.5). The new optimum value is 13.5 percent which
is the moisture corresponding to the next highest curve which is Curve K.
The compaction, the
difference in optimum moisture content, and the zero air voids are calculated
on lines 22 to 24.
Figure 1015.03.F
- Zero Air Voids Curve
Figure
1015.03.G - Outline for Using Forms CA-EW-5 and CA-EW-6 (1 of 2)
Figure
1015.03.H - Outline for Using Forms CA-EW-5 and CA-EW-6 (2 of 2)
Figure
1015.03.I - Compaction and Testing Guide
This section describes how to
perform compaction testing for materials used as granular soil, sand,
structural backfill Type 1 or 2, 304, 411, select granular backfill for MSE
walls, granular material Type A, B, C, D or F, or any materials that requires a
test section.
The dry density of the
material is used for compaction control.
The wet density method is no longer used.
Moisture-density Proctor
curves were originally developed for use on cohesive (clays and silts)
soils. Errors or complications arise
when trying to extrapolate these principles to other materials. This is the reason the Engineer or Inspector is
given the latitude to choose density requirements that are based on the test
section results.
A one-point Proctor method
using the typical density curves may be used for granular soils. The top curves of the Ohio Typical Density
Curves A through E are usually chosen in this case. These curves will only work in a very limited
number of cases. This method should only
be used as a last resort.
These materials must have a
moisture-density curve made a few weeks before the Contractor proposes to use
the material. Curves may be made in the
field or by the Laboratory.
Making a moisture-density
curve for these materials is the same procedure explained in Section 1015.01.B. A typical moisture-density curve for a
granular material is shown in Figure 1015.04.A.
Figure
1015.04.A - Typical Granular Moisture-Density Curve
The district should contact
the Office of Geotechnical Engineering
to have a moisture-density curve made.
The maximum dry density and
optimum moisture content data obtained from this curve may or may not work in
the field. The following are examples
and further explanation of some of the problems associated with the density
control of these materials.
It may not be possible to
obtain the maximum density of the curve no matter how or with what equipment
the Contractor uses to compact the material.
This is particularly true for sandy material with silt fines.
The Proctor mold used to
produce the moisture-density curve confines the sand in all directions. In the field, since sand doesn't interlock or
knit together well without being confined, the roller will squeeze the material
laterally. The Proctor maximum densities may not be obtained in the field.
The sand may not even support
the weight of the roller. The lab and
field confining pressures and compactive effort are not compatible in this
case.
This is shown in Figure 1015.04.B
Use the test section maximum
density.
In this case, the maximum dry
densities obtained in the field, using the test section method, often exceed
the maximum dry density of the moisture-density curve.
The 304 type material is well
interlocked and allows the roller to transfer more energy, compactive effort,
or load to the material.
This roller load or energy is
much larger than the Proctor hammer load of 5.5 lbs. (2.5 kg) dropped 12 inches
(305 mm) in three lifts.
This is shown in Figure 1015.04.B.
Figure
1015.04.B - Maximum Density Problems
Use the test section maximum
density.
If the material is being
compacted on a soft foundation, then the maximum density cannot be
achieved. Excessive rolling will only
result in pumping and creating an unstable foundation.
This applies to all types of
materials. You cannot compact good material over bad material and expect to
achieve a maximum density. You cannot
compact material on jello-type material to a maximum
density either. The maximum test section
densities, if taken at all, would be less than the maximum curve value.
There are a variety of
locations where light equipment is used to compact material. Some examples are for:
1. Pipe backfill.
2. Manhole backfill.
3. Around abutments.
4. MSE walls.
The potential maximum density
is limited to the type of equipment used to compact this material in these
confined spaces.
Throughout the specifications
for these items, ODOT requires minimum compaction equipment weight for these
areas where a test section is used for compaction acceptance.
The maximum density that can
be achieved is proportional to the heaviest equipment that can be used in these
locations. The maximum density that can
be achieved in these locations is usually less than the moisture-density curve
value.
The granular material should
be brought on site at or near optimum moisture.
When this is not the case, moisture should be added before rolling
occurs. This is particularly important
for 304 gradation materials since this material cannot readily absorb water.
In 304.03, it is required
that the stockpile of 304 material have a moisture content of at least 2
percent below optimum.
Optimum moisture from the
Proctor moisture-density curve of granular materials is not always
correct. Sometimes the granular material
begins to roll or pump when the material is compacted at or near optimum
moisture obtained from the moisture-density curve. This is caused by excess water in the
material and the difference between the field and curve confining forces. In this case, dry the material until
stability is achieved; usually 1 to 3 percent below optimum will work.
A granular moisture-density
curve should always be used to estimate the maximum density and optimum
moisture. When using these materials,
the Proctor moisture-density curve is used as a guide; the exact maximum density
and optimum moisture can only be found in the field.
The test section method of
compaction acceptance compensates for:
1. Material differences.
2. Moisture-density curve and potential field density
differences.
3. Moisture problems.
4. Soft foundations.
5. Confined construction.
The maximum density
determined in the field is relative to all of the above.
The equipment used for
compaction testing is listed in 1015.04.
The compaction testing is the
same as in section 1015.02.D,
except for the following:
1. A Proctor is not taken for every test.
a. Only used to obtain the moisture-density curve.
2. The “Backscatter Mode” on the gauge is used.
a. Ensure that the surface voids are all filled or the
surface texture is the same.
b. Variation in the measurements will result.
3. Use Form CA-EW-5.
Throughout the
specifications, you will find minimum roller weight requirements when a test
section method is used for acceptance.
The following is from
C&MS 203.06.A, page 92.
“For soil or granular material, when a test section is used, use a
minimum compactive effort of eight passes with a steel wheel roller having a
minimum weight of 10 tons (9 metric tons).”
The maximum potential
obtained in the field is relative to the roller weight used in the test
section. Therefore, minimums were
established to fit the field conditions.
You will notice that the confined areas have a much lower minimum weight
and less maximum acceptance value.
Do not be confused by the
word centrifugal force. It is only the
effective weight when including the vibration of the equipment.
Method A is used when the
moisture-density curve can be established to estimate the maximum density and
optimum moisture.
The following is an outline
of the procedure:
1. Test section size is 400 square yards (for embankment
or aggregate base).
2. Spread the material at the correct lift thickness.
a. Usually 6 to 8 inches.
3. Moisture content at - 1 to + 1 of optimum.
a. Water or dry throughout the lift.
b. Reduce moisture if unstable.
4. Compact with two passes.
5. Take a compaction test.
a. Mark the location with paint.
b. Record on line 6 of form CA-EW-5.
6. Compact with one more pass and continue testing until:
a. No further increase in density.
b. Or the density decreases.
7. Once a maximum is obtained.
a. Make two additional passes and take one additional
test.
b. Verifies the maximum value (Verification Test).
8. Record the total number of passes.
a. Use line 9 of CA-EW-5.
9. Use this number of passes or the specification minimum
in the production area.
10. Compact the production area to at least 98 percent of
the test section maximum.
There are statements
throughout the specifications that require a minimum number of passes. Experience has shown that these minimum
passes for the different materials result in more uniform compaction in the
production areas.
If the specification calls
for 8 passes, use the 8 passes even though the test section may show that 6
passes are needed to obtain a maximum.
More production area tests will pass by using these minimum passes.
There are also statements
throughout the specifications that allow a decrease in minimum number of
passes, such as:
“The Engineer may reduce the minimum passes if the passes are
detrimental to compaction.”
There are also statements
about making a new test section when conditions change.
“Construct a new test section if the pipe type, bedding material,
backfill material, or trench conditions change.”
All of these statements allow
the Engineer to control the work to meet the field conditions and to obtain
maximum densities.
Table 1015.06.A – Test Section Value Examples (‘X’
denotes Maximum Used)
Passes |
2 |
3 |
4 |
5 |
6 |
Verification Passes (2) |
Density |
126 |
134 |
135 |
140X |
122 |
125 |
|
110 |
108 |
112 |
116 |
116X |
109 |
|
120 |
129 |
132 |
130 |
|
145 (Take more Tests) |
This type of test section is
used when a moisture-density curve cannot be made or is not available at the
time of construction. Recycled
materials, such as some foundry sands or fly ash can be tested this way. Since the maximum density or optimum moisture
are unknown, we have to create the field curve.
Use the same procedure as in
Section 1015.05,
except for the following.
1. Place the material in the required lifts.
a. Bone dry (0 to 3 percent).
2. Compact and test until:
a. A maximum value is reached.
b. Record the density on line 6 on the CA-EW-5.
c. Record the number of passes on line 9.
3. Place new material.
a. At a new location.
b. At a moisture content 2 percent higher.
4. Compact and test to a maximum value.
5. Repeat the procedure.
a. At higher moisture until.
i.
Maximum value is
achieved.
ii.
Two test sections
have the same or lower densities.
iii.
Material becomes
unstable.
6. Use this maximum density, optimum moisture, and number
of passes in the production areas.
Figure
1015.06.A - Typical Fly Ash Curves
This test section is used for
open graded material, such as non-stabilized drainage base. It can also be used for open graded aggregate
bases where the surface texture is very open and/or non-uniform.
The test section procedure is
the same as detailed in 1015.05 except for the following:
1. Place and compact the material at 1.5 percent above
saturated surface dry (SSD).
2. Construct a test section.
a. 400 square yards.
b. Take three tests.
c. Average them.
d. Compare the averages.
3. The maximum dry density is reached when:
a. A maximum density average is achieved.
b. The aggregate breaks.
c. Whichever comes first.
4. Take 10 tests in the control section.
a. Use 98 percent of this density as the control section
maximum.
5. For acceptance.
a. Take five tests in a 5,000 square yard lot.
b. This average must be greater than 98 percent of the
control section maximum.
Compaction testing for shale will
depend on the durability of the shale.
Perform the durability test (Bucket test) outlined in 703.16.D in the
C&MS. The compaction testing is
directly associated with the results. It
provides a ready means to determine what test method to use for compaction
acceptance.
In practice, different
materials will always be mixed together in a fill situation. However, the durability test gives a good
indication of how the material should break down during compaction and is an
excellent way to determine how to test the compaction of the shale.
Compaction acceptance is
always based on the dry density of the material. After the material is compacted, the dry
density does not change with the addition or reduction of water, while the wet
density does increase with the addition of water and decrease as the material
dries.
Use Forms CA-EW-5 and CA-EW-6 for recording
and reporting results of compaction tests.
Retain these test reports in the project files. Keep these test reports in the folders of the
items of work.
This section outlines the lot
size and number of tests that are used on each lot for acceptance.
Under normal field
conditions, the number of density and moisture checks required should not be
that great after the initial period of adjustment, assuming that the work is
proceeding smoothly and materials being compacted are uniform.
The Engineer and Inspector
will learn to judge the moisture content of the material quickly by appearance
and feel. If adequate densities are
obtained and the proper moisture content is maintained, the job of inspection
may consist of deciding on the number of passes of the roller required for
satisfactory test section density and ensuring that this number of passes is
made.
Under such conditions, only
one or two density checks per day may be required. Where conditions are more variable, density
and moisture checks may be needed as often as once an hour. The Engineer and Inspector can determine the
exact number of checks required.
1. Document all materials, inspection, and compaction
information on Form CA‑EW‑12.
2. For Items 203, 204, 205, 206, 840, 503, 611, Soil Embankment, and all items
that 203 Embankment is specified:
a. If less than 10 percent of material passes the
3/4-inch sieve, document on form CA-EW-5.
b. If more than 10 percent, but less than 25 percent of
the material passes the 3/4-inch sieve, document on form CA-EW-6.
c. If more than 25 percent of the material passes the
3/4-inch sieve, document on form CA-EW-5.
3. Items 203, Granular Embankment; 203 Granular Material Types A, B, C,
D, or F; Item 304, 411, 503, Select Granular Backfill for
MSE Walls; and Structural Backfill and Granular Embankment, document on form CA-EW-5.
SUPPLEMENT
1015
Compaction Testing of Unbound Materials
December 31, 2012
1015.01 General
1015.02 Definitions
1015.03 Referenced Standards
1015.04 Apparatus
1015.05 Forms
1015.06 Procedure
1015.07 Shale
1015.08 Compaction Acceptance
1015.09 Number of Tests
Typical Moisture Density Curves – Set C – May 1949
Aggregate Correction Chart
1015.01 General. Compaction testing of unbound materials
consists of determining the in-place density of a material (such as
fine-grained soil, granular material, or shale) and calculating the percent
compaction of the material based on a maximum dry density. Depending on the material, determine the
maximum dry density using either the one-point Proctor method, the one-point
Proctor with aggregate correction method, or the test section method.
Perform compaction
testing according to this supplement for Items 203, 204, 205, 206, 304, 411, 503, 611, 840 and other items when this
supplement is specified.
The Department will
perform the compaction tests unless specifically stated otherwise in the
Contract Documents.
Fine-grained soil. A soil with more than 35 percent of the material
finer than the No. 200 sieve.
Fine-grained soils include soils classified as A-4a, A-4b, A-5, A-6a,
A-6b, A-7-5, and A‑7‑6 according to AASHTO M 145 (as modified by the Department’s Specifications for Geotechnical Explorations).
Granular material. A soil, aggregate or stone with 35 percent or less
of the material finer than the No. 200 sieve.
Granular material includes coarse aggregate; granular material types A
through F; sand; select granular backfill for MSE walls; Items 304, 410, 411, and
614; and material classified as A-1-a, A-1-b, A-2-4, A-2-5, A-2-6, A-2-7, A-3,
and A-3a according to AASHTO M 145 (as modified by the Department’s Specifications for Geotechnical Explorations).
Roller pass. When used in the context of compacting soil and
unbound materials, one roller pass is when compaction equipment travels over a
given point on a surface one time. The
compaction equipment may consist of a roller or may also consist of other types
of equipment, such as a vibratory plate compactor.
Test
Method |
AASHTO Designation |
Moisture-Density Relations of Soils (Standard
Proctor) |
|
Correction for Coarse Particles in the Soil
Compaction Test |
|
Family of Curves – One Point Method |
|
In-Place Density and Moisture Content of Soil and |
1015.04 Apparatus. Use a nuclear density/moisture gage and other
equipment required by AASHTO T 310. Use a mold, rammer, balance or scale,
straightedge, sieves, and other equipment that conforms with AASHTO T 99, Method C.
1015.05 Forms. Use the
following ODOT forms to record compaction test results.
One-point Proctor Method...................................................... CA-EW-5
One-point Proctor with Aggregate Correction Method.......... CA-EW-6
Test Section Method A and B................................................ CA-EW-5
Moisture Density Curve.......................................................... CA-EW-4
A. General. Depending on
the material type, determine the in-place density and maximum dry density using
the mode of operation and method as shown in the following table. The test section method may also be used for
fine-grained soils instead of the one-point Proctor method if justified by the
material or site conditions.
TABLE 1015.06-1 Compaction Testing Procedure
Material Type |
Nuclear Gage Mode of Operation |
Method of Determining |
Fine-grained soil, percent
oversize particles (retained on ¾-inch sieve) |
||
less than 10% |
Direct transmission |
One-point Proctor |
10 to 25% |
Direct transmission |
One-point Proctor with
aggregate correction |
more than 25% |
Backscatter |
Test section |
Granular material |
Backscatter |
Test section |
Shale |
(See 1015.07) |
(See 1015.07) |
B. In-place Density and Moisture. Determine the
in-place density and moisture content using a nuclear gage according to AASHTO T 310 and as described below.
1. Standard
count. Take a standard count at the beginning of
each day the gage is in use. To take a standard count, place the reference
block on a flat surface at least six feet (2 m) from any building or structure
and at least 30 feet (10 m) from any other radiation source (like another
nuclear gage). The flat surface must have
a density greater than 100 lb/ft³ (1600 kg/m³), so
asphalt, concrete, compacted aggregate, compacted soil and similar materials
are acceptable, but truck beds, tailgates, tables, etc. are not. Place the gage on the reference block such
that it rests between the raised edges of the block and the right side of the
gage is firmly against the metal butt plate on the block. Ensure the source rod is in the “safe”
position and start the standard count.
If the standard count passes, accept the new standard. If the standard count does not pass, do not accept it. Check to see if all the requirements above were met. If so, take another standard count. If the second standard count also fails, erase all the stored standard counts and take four new sets of standard counts. Record the standard counts (both density and moisture) on the compaction testing form.
2. Preparation
of surface. Remove all loose and disturbed material from
an area large enough to accommodate the gage (for rough surfaces compacted with
a footed roller, this may mean removing around 6 inches of material). Smooth
the area with the scraper plate. Fill any voids in the smoothed surface with
fine sand or fine-grained soil from nearby the test location.
If using the direct transmission mode to determine in-place density, place the scraper plate on the surface and press down firmly. Place the extraction tool over one of the guides on the scraper plate and then place the drill rod through the guide. Hammer the drill rod two inches (50 mm) deeper than the measurement depth. (Note that many drill rods have markings which include the additional two inches). Mark at least two edges of the scraper plate to make it easier to correctly place the gage. Remove the drill rod by pulling straight up and twisting the extraction tool. Pick up and remove the scraper plate.
3. Taking a
measurement. While taking a
measurement, ensure there are no other radiation sources (such as other nuclear
gages) within 30 feet (10 m) of the gage.
If using the backscatter mode, place the gage on the prepared surface, extend the source rod to the backscatter position, and take a measurement.
If using the direct transmission mode, slightly tilt the gage and extend the source rod two inches (50 mm). Place the source rod into the hole formed by the drill rod, and lower the gage to the surface. Then extend the source rod to the required measurement depth. When testing subgrade compaction (Item 204 or 206) use a measurement depth of 12 inches (300 mm). When testing compaction of embankment or backfill materials, use a measurement depth of 8 inches (200 mm) (other measurement depths may also be used depending on lift thickness and site conditions.) Pull the gage to the right so that the side of the source rod that faces the center of the gage is in firm contact with the side of the hole. Take a measurement.
For both modes of operation, use a count time of at least one minute. A four minute count time may also be used for more accuracy.
Record the in-place readings for wet density, dry density, and percent moisture on the compaction testing form.
Return the source rod to the “safe” position and remove the gage.
4. Trench
correction. When performing compaction testing in a
trench, follow the gage manufacturer’s recommended procedure to perform a
trench correction (also called a trench offset).
The nuclear gage determines moisture content by measuring reflected slow neutrons, and it determines density in the backscatter mode by measuring reflected gamma photons. When operating the gage in a trench, the gage will measure additional reflected gamma photons and neutrons that “bounce” off the sides of the trench, thus increasing the density and moisture content readings. The trench correction procedure typically consists of taking two standard counts on the reference block, one outside of the trench and one inside of the trench, before determining the in-place density and moisture content of the trench backfill.
5. Moisture
correction. The moisture content
reading from the gage may be greater than the actual moisture content when
testing soil that contains significant amounts of organic material, coal,
gypsum, cement, lime, lime kiln dust, fly ash, or reclaimed asphalt concrete
pavement (RACP). When directed by the
Engineer, correct the moisture content according to the gage manufacturer’s
recommended procedure.
The nuclear gage determines moisture content by measuring the amount of hydrogen present in the material. If the material being tested contains significant amounts of hydrogen in a form other than free water (such as soil containing organic material, coal, gypsum, cement, lime, lime kiln dust, fly ash, or RACP), then the gage will report a moisture content reading that is greater than the actual moisture content. As a result, the gage will also report a dry density reading that is less than the actual dry density. The correction procedure typically consists of comparing the gage moisture content reading to the actual moisture content (determined using other applicable test methods) and determining the offset correction.
Do not perform a moisture correction on chemically
stabilized soil (Items 205 and 206) unless directed by the
Engineer. The specifications for Items
205 and 206 account for the fact that the cement, lime, or lime kiln dust mixed
into the soil reduces the actual moisture content by binding with free water
while not reducing the moisture content reading from the nuclear gage.
C. Maximum Dry Density. Determine the
maximum dry density using the method specified in Table 1015.06-1 for the
material type being tested. The methods
are described below.
1. One-point
Proctor. Determine the maximum dry density and optimum
moisture content for the material according to AASHTO T 272, Method C, except as modified below. For the family of curves, use the “Typical
Moisture Density Curves – Set C – May 1949” included with this document.
Perform a one-point Proctor test for each and every compaction test. Obtain a soil sample from the area that was directly under the gage during the in-place density and moisture measurement. Prepare the sample by sieving it through a ¾-inch (19 mm) sieve. If a significant amount of oversize particles are retained on the ¾-inch (19 mm) sieve, calculate the percentage of oversize particles as compared to the total sample weight and check to see if an aggregate correction is required.
Do not dry the sample. Use the sample at the in-place moisture content.
Place the Proctor mold on a concrete block or concrete surface when compacting the sample.
Use the wet density of the Proctor sample and the percent moisture from the in-place moisture reading to mark a point on the family of curves. If the point falls on one of the curves, use the maximum dry density and optimum moisture content for that curve. If the point falls in the space between two curves, use the higher curve to determine the maximum dry density and optimum moisture content. Record the curve letter, the maximum dry density and the optimum moisture content on the compaction testing form.
2. One-point
Proctor with Aggregate Correction. Determine the maximum dry density and optimum
moisture content for the material as described above for the one-point Proctor
method. If the amount of oversize
particles that are retained on the ¾-inch (19 mm) sieve is greater than or
equal to 10 percent of the total sample and less than or equal to 25 percent,
adjust the maximum dry density and optimum moisture content to account for the
fact that the oversize particles were removed from the in-place soil
sample. Calculate the corrected maximum
dry density according to AASHTO T 224, using either the
following equation or the Aggregate Correction Chart included with this
document.
MDDc= |
62.4 Gs MDD |
MDD %C+62.4 Gs (1-%C) |
Where:
MDDc = corrected maximum dry density
MDD = maximum dry density from one-point Proctor method
Gs = bulk specific gravity (oven-dry basis) of oversize
particles retained on
¾-inch (19 mm) sieve
%C = percent of oversize particles (expressed as a decimal, e.g. 12% = 0.12)
After calculating the corrected maximum dry density, determine the corrected optimum moisture content by using the Typical Moisture Density Curves. Find the lowest curve that has a maximum dry density equal to or greater than the maximum dry density. Use the optimum moisture content for that curve as the corrected optimum moisture content.
3. Test Section. Determine the maximum dry density of the material by constructing a test section. Use Test Section Method A when the moisture-density curve (AASHTO
Table
1015.06-2 Approximate size of test section
2. Compact the material in the test section
with two roller passes.
3. Measure the in-place density and moisture
content according to 1015.06.B.
5. Compact the material in the test section
with one more roller pass.
6. Measure the in-place density and moisture
content again.
1. Place the material in the test section at a
moisture content from 0 to 3 percent.
2. Compact the material in the test section
with two roller passes.
5. Compact the material in the test section
with one more roller pass.
D. Calculations. Calculate the percent compaction by dividing
the in-place dry density measurement by the maximum dry density for the
material. Use the corrected maximum dry
density if an aggregate correction was required.
1015.07 Shale. The compaction testing method for shale
depends on the durability of the shale. Test shale for durability according to 703.16.D to determine if the shale is durable
or nondurable shale. Use the results
from the durability testing to determine the appropriate compaction testing
method for shale according to the following table. Perform the compaction testing according to 1015.06.
TABLE
1015.07-1 SHALE Compaction Testing
Procedure
1015.08 Compaction Acceptance. The minimum
compaction requirement as a percentage of the maximum dry density is given in
the corresponding specification for the material. All compaction percentages are calculated
based on the dry density of the material.
1015.09 Number of Tests. Divide the work into lots as
shown in the following table. Perform the minimum number of compaction tests as
shown in the table. When a lot is
measured in square yards (square meters) and the material is placed in multiple
lifts, perform at least the minimum number of compaction tests on each lift.