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APPENDIX C
DIAMETRAL TEST PROCEDURE FOR RESILIENT MODULUS
OF ASPHALT CONCRETE
C - 1
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APPENDIX C
PROPOSED PROTOCOL
1. SCOPE
I.1 General
This proposed protocol describes procedures for the determination of the resilient
modulus of hot mix asphalt concrete (HMA), using repeated load indirect tensile
test techniques. The procedure involves resilient modulus testing over a range of
temperatures and loads.
I.2 Testing Prerequisites
Resilient modulus testing shall be conducted after system response has been
verified by testing synthetic specimens, as outlined in section 8. ~ ofthis protocol.
I.3 Sample Size
Resilient modulus testing shall be conducted on 4 inch diameter specimens that are
1.5 inches to 4 inches in thickness; for medium (or fine) gradation mixes. For base
courses or large-stone surface mixes a 6 inch diameter specimen with thickness
between 3 and 4.5 inch is recommended. Desired thickness for a 4 inch diameter
specimen is 2.5 inches and for a 6 inch diameter specimen desired thickness is 3.75
inches.
I.4 Pretest Tensile Strength
Prior to performing the resilient modulus test the indirect tensile strength shall be
determined for one test specimen taken from the same layer and as close as
possible to the location of the core specimenfs) to be tested for resilient modulus.
For lab specimens, a sample having the same mix properties will be selected for
indirect tensile strength testing. The indirect tensile strength test is performed as a
basis for selecting the loading levels for the resilient modulus testing. Test shall be
performed in accordance with attachment A of the SHRP P07 protocol (November
I, 19921.
I.S Definitions
The following definitions are used throughout this protocol:
Layer - that part of the pavement produced with similar material and
placed with similar equipment and techniques. The layer thickness can be
equal to or less than the core thickness or length.
(b) Core - an intact cylindrical specimen of pavement materials which is
removed from the pavement by drilling and sampling at the designated
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core location. A core may consist of, or include, one, two or more
different layers.
(d)
Test Specimen - that part of the layer which is used for, or in, the specified
test. The thickness of the test specimen can be equal to or less than the
layer thickness.
Haversine Shaped Load Form - the required load pulse form the resilient
modulus test. The load pulse is in the form (] - cos O)/2 and the cyclic
load is varied from the contact load (Pcon~ac~) to the maximum load (Pma,`~'
as shown in Figure C- ~ (from SHRP P07 protocol).
(e) Maximum Applied Load (PmaX) - the maximum total load applied to the
sample, including the contact and cyclic (resilient) loads.
Pmax = Pcontact + Pcyclic
(g)
(h)
Contact Load (PContact) - the vertical load placed on specimen to maintain a
positive contact between the loading strip and the specimen.
At 41°F
At 77°F,
PContact = 0.05 PmaX
PContact = 0.04 PmaX
At 104°F,
PContact = 0.04 Pma,,, not less than 5 Ibs, but not more than 20 Ibs.
Cyclic Load (Resilient Vertical Load, PCyclic) - load applied to a specimen,
respectively, which is directly used to calculate resilient modulus.
Pcyclic = Pmax ~ Pcontact
Instantaneous Resilient Modulus - determined from the deformation-time
plots (both horizontal and vertical) as described herein.
To determine the instantaneous deformation values, it is recommended to
perform regression in three portions of the deformation curve:
I. Linear regression in the straight portion of the unloading path
2.
Regression in the curved portion that connects the unloading path
and the recovery portion to yield the following hyperbolic
equation:
Y=a+b/X
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where
X =
Y = deformation value,
time, and
a, b = regression constants.
Regression in the recovery portion between 40% and 90%
(recommended range) of rest period to yield a hyperbolic
equation. A tangent should be drawn to this hyperbola at the point
corresponding to 55% (recommended point) of the rest period.
Two linear equations, one from the unloading path and the other from the
tangent of the hyperbola in the recovery period, shall be solved to
determine the intersection. Then the point on the hyperbolic curve
.. . .. .. ~ . ~ . . .. , ~ .
(i,
corresponding to the time coordinate ot the intersection tior convenience,
say point A) is selected to determine the instantaneous deformation by
subtracting the deformation at the point A from the peak deformation.
Total Resilient Modulus - determined from the deformation-time plots
(both horizontal and vertical) by subtracting deformation obtained at the
end of one load-unload rest period cycle, as determined by taking the
average of deformation values obtained for the time period between 85%
completion to 95% completion of the rest period from the peak
deformation values. This value includes both the instantaneous
recoverable deformation and the time-dependent continuing recoverable
deformation during the rest-period portion of one cycle.
2. APPLICABLE DOCUMENTS
SHRP protocol P07
3. SUMMARY OF METHOD
Resilient Modulus for Asphalt Concrete
3.! The repeated-Ioad indirect tension resilient modulus test of asphalt concrete is
conducted through repetitive applications of compressive loads in a haversine
waveform. The compressive load is applied along a diametrical plane of a
cylindrical Asphalt Concrete specimen. The resulting horizontal and vertical
deformations are measured. Values of resilient Poisson's ratio shall be calculated
using recoverable vertical and horizontal deformations. The resilient modulus
values are subsequently calculated using the calculated Poisson's ratio.
3.2 Two separate resilient modulus values are obtained. One, termed instantaneous
resilient modulus, is calculated using the recoverable horizontal deformation that
occurs during the unloading portion of one load-unIoad cycle. The other, termed
total resilient modulus, is calculated using the total recoverable deformation which
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includes both the instantaneous recoverable and the time-dependent continuing
recoverable deformation during the unload or rest-period portion of one cycle.
3.3
For each resilient modulus test, the following general procedures must be
followed:
(a)
~ ne tensile strength Is determined on a test specimen at 77 ~ 2°F using the
procedure described in attachment A to SHRP P07 protocol. The value of
tensile strength obtained from this procedure is used to determine the
indirect tensile stress and corresponding compressive load to be
respectively applied to the test specimens during the resilient modulus
determinations.
(b)
The test specimenfs) are to be tested along one diametral axis at one rest
period (i.e., 0.9 seconds) and at testing temperatures of 4 l, 77 and 1 04°F
plus or minus two degrees F (5, 25, and 40°C plus or minus one degree C).
For each test temperature, repetitive haversine load pulses of 0.! second
duration followed by a rest period of 0.9 seconds between load pulses are
applied to the individual test specimens. The magnitude of the load pulse
will be selected to produce a predefined indirect tensile stress on the
specimen based on a percentage of the indirect tensile strength (see section
3.3(a) above). The temperature testing sequence includes initial testing at
4 ~ OF followed by testing at 77°F, and final testing at 1 04°F.
After completion of resilient modulus testing at 104°F, the test specimen
shall be returned to 77°F and an indirect tensile strength shall be
performed in accordance with attachment A of the SHRP P07 protocol.
This test is performed to determine the tensile strength of the specific
specimen actually used in resilient modulus testing. For these specimens
the loading axis shall be 90° to the axis used for modulus determinations.
SIGNIFICANCE AND USE
Resilient modulus can be used in evaluations of materials quality and as input for pavement
design, evaluation and analysis. With this method, the effects of temperature and load on
resilient modulus can also be investigated.
s. SPINS
5.1 Testing Machine
The testing machine shall be a top loading, closed loop, electrohydraulic testing
machine with a function generator which is capable of applying a haversine shaped
load pulse over a range of load durations, load levels, and rest periods.
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5.2 Loading Device
The loading device should be capable of testing 4 inch and 6 inch diameter
specimens with thickness up to 4.5 inches. The device should be compact enough
to be used within the environmental chamber. It should have a fixed bottom
loading plate and a moving upper loading plate. The movement of the upper plate
should be guided by two columns, one on each side of the specimen and
equidistant from the loading axis and the loading strips, to ensure it has minimal
translational or rotational motion during loading of the specimen. The guide
columns shall have a frictioniess bearing surface that shall be kept well lubricated.
The surfaces of the guide columns shall be frequently inspected for any grooves
caused due to friction. Alignment of the device, within the loading system, shall
be achieved so that such friction is limited to the minimum possible extent. The
upper plate shall be rigid enough to prevent any deflections during loading. If
heavyweight plates are used to achieve rigidity, the testing system should be able
to counteract all the weight, such that no more than 2 Ibs. of load is transferred to
the specimen when load is not being applied. It is recommended that high strength
material be used to achieve rigidity and keep the weight small. The loading strips
shall preferably be perpendicular to the line connecting the two guide columns, so
that visual alignment of the sample in the device is easier.
5.3 Temperature Control Systems
The temperature-control system should be capable of maintaining temperature
control within 2°F (~.~°C), at settings ranging from 41°F (5°C) to 104°F (40°C).
The system shall include a temperature-controlled cabinet large enough to house
the loading device, and a cabinet adequate to pre-condition at least three test
specimens at a time prior to testing.
5.4
Measurement and Recording System
The measuring and recording system shall include sensors for measuring and
simultaneously recording horizontal and vertical deformations and loads. The
system shall be capable of recording horizontal and vertical deformations in the
range of 0.00001 inch (0.00025 mm) of deformation. Load cells shall be
accurately calibrated, with a resolution of 2 Ibs. or better.
5.4.! Data Acquisition - The measuring or recording devices must provide real
time deformation and load information and should be capable of
monitoring readings on tests conducted to ~ Hz. Computer monitoring
systems are recommended. The data acquisition system shall be capable
of collecting at least 200 scans per second (a scan includes all deformation
and load values at a given point of time). Capability to have real-time
plots (simultaneous to the data collection by the computer monitoring
system) shall also be provided to check the progress of the test. If strip
chart recorders are used without computer monitoring systems, the
plotting scale shall be adjusted such that there is a balance between the
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scale reduction required as a result of the pen reaction time and the scale
amplification needed for purposes of accurate measurement of values from
a plot.
Actual load values, and not the intended load values, shall be used for
calculation purposes and so the data acquisition system shall also be
capable of monitoring the load values continuously cluring testing.
S.4.2 Deformation Measurement - The vertical deformation shall be measured
on the surface of the specimen by mounting a LVDT between gage points
along the vertical diameter. The gage length shall be three quarters the
diameter of the specimen. if possible, two EVD[s, one each on the front
and back faces of the specimen, should be used and the deformation
averaged. Extensometers (or a comparable mountable device) should be
used for the measurement of the horizontal deformation. The EVDrs
shall be frequently calibrated, preferably each day before testing.
Extensometers, if used, should also be calibrated from time to time. The
surfaces on which the knife edges of the extensometer assembly rests
should be kept smooth and free of grooves.
5.4.3 Load Measurement- The repetitive loads shall be measured with an
electronic load cell with a capacity adequate for the maximum required
loading, and a sensitivity of 0.5% of the intended peak load. At higher
temperatures, this limit can be relaxed to a sensitivity of ~ ~ Ibs.
During periods of resilient modulus testing, the load cell shall be
monitored and checked once a month with a calibrated proving ring to
assure that the load cell is operating properly. Additionally, the load cell
shall be checked at any time that the QA/QC testing with in-house
synthetic specimens (section 8.1 ) indicates a change in the system
response or when there is a suspicion of a load cell problem.
5.5 Loading Strips
Steel loading strips, with concave sample contact surfaces, machined to the radius
of curvature of a 4.000 ~ 0.004 inch diameter specimen or a 6.000 ~ 0.006 inch
diameter specimen, are required to apply load to the test specimens. The contact
area of the loading strip shall be 1/2 inches wide and 3/4 inches wide for 4 inch and
6 inch diameter specimens respectively. The outer edges of the curved surface
shall be filed lightly to remove sharp edges that might cut the specimen during
testing. Thin lines should be drawn along the length of the strip at its center, to
help in alignment. Also, appropriate markings should be made so as to center the
specimens within the length of the strips. This could be either done by matching
the center of specimen with a mark at the center of the strip or by positioning the
specimen between two marks at the ends of the specimen thickness, or both.
5.6 Marking and Alignment Devices
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A marking device shall be used to mark mutually perpendicular axes on the front
and back faces of the specimen through the center. The device shall be capable of
marking axes on different sizes (thickness and diameter) of specimens. The axes
shall be simultaneously marked on the front and back faces of the specimen to
ensure that the axes on the front and back lie in a single plane.
An alignment device shall be used to position and place the vertical EVDT along
the vertical diameter of the specimen and hold it there, until the glue that holds the
EVDT cures. It shall be easily removable, without disturbing the EVDT (once He
glue cures), and shall not be destructively mounted on the specimen. The device
shall preferably have the capability to mount the EVDT at different gage lengths
but mainly at a gage length of three quarters of the diameter of the specimen. The
EVDT when positioned shall be parallel to the surface of the specimen and in line
with the vertical diameter of the specimen. The EVDT shall be as close to (but not
touching) the surface of the specimen so as to minimize the bulging effect. To
ensure uniform test results, a height of 0.2 inch is recommended. The axis of
EVDT shall not be at a distance greater than 0.25 inch from the surface of the
specimen.
6. TEST SPECDIENS
6.1
Core specimens - Cores for test specimen preparation, which may contain one or
more testable layers, must have smooth and uniform vertical (curved) surfaces, and
must be no less than 3.X5 inch or more than 4.15 inch in diameter. Cores which
are obviously deformed or have any visible cracks must be rejected. Irregular top
and bottom surfaces shall be trued up as necessary, and individual layer specimens
obtained by cutting with a diamond saw using water or air as a coolant.
It is recommended that base course or large-stone mixes shall be no less than 5.85
inches or more than 6. ~ 5 inches in diameter.
6.2 The test specimens designated for testing shall not be more than 4 inches in
thickness. However, for base course or large-stone mixes the thickness shall not
be greater than 4.5 inches. If a core specimen has more than one layer the layers
shall be separated at the layer interface by sawing. Layers containing more than
one lift of the same material as placed under contract specification, may be tested
as a single specimen. Traffic direction shall be marked on each layer after cutting,
to maintain the correct orientation. Layers too thin to test (less than I.5 inch for 4
inch diameter specimen or 3 inches for 6 inch diameter specimen), as well as any
thin surface treatments, shall be removed and discarded. However, 6 inch diameter
specimens with thickness less than 3 inches but greater than I.5 inch, shall be
reduced to a 4 inch diameter specimen and tested where possible.
A test specimen shall consist of a single pavement material or layer greater than
I.5 inches in thickness. The desired thickness for testing is approximately 2.5
inches for a 4 inch diameter specimen and 3.75 inches for a 6 inch diameter
specimen. If the thickness of a particular AC layer scheduled for testing is one
inch or more greater than the desired testing thickness, then the specimen to be
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used for testing shall be obtained from the middle of the AC layer by sawing the
specimen. If the thickness of a core from an AC layer is between I .S and 4 inches
for a 4 inch diameter specimen and between 3 and 4.5 inches for a 6 inch diameter
specimen, and has relatively smooth front and back faces then no sawing is
required and the specimen for this layer may be tested as is.
6.3
6.4
7. PROCEDURE
7.! General
Diametral Axis - Marking of the diametral axis to be tested shall be done using a
suitable marking device as described in section 5.6. The axis shall be parallel to
the traffic direction symbol (arrow) or "T" marked during the field coring
operations. This diametral axis location can be rotated slightly, if necessary, to
avoid contact of the loading strips with abnormally large aggregate particles or
surface voids; or to avoid the mounting of the vertical EVDT over large surface
voids. Rotation of test axis is also required if the surfaces to be loaded taper by
more than .005 inch from parallel. Finally, the mid-thickness of the specimen shall
be marked if necessary, to aid in centering the specimen on the loading strips.
The thickness (t) of each test specimen shall be measured to the nearest 0.01 inch
(0.25 mm) prior to testing. The thickness shall be determined by averaging four
measurements located at ~J4 points around the sample perimeter, and 1/2 to ~ inch
in from the specimen edge.
The diameter (D) of each test specimen shall be determined prior to testing to the
nearest 0.01 inch (0.25 mm) by averaging diametral measurements. Measure the
diameter of the specimen at mid-height along (~) the axis parallel to the direction
of traffic and (2) the axis perpendicular (90 degrees) to the axis measured in (~)
above. The two measurements shall be averaged to determine the diameter of the
test specimen.
The asphalt cores shall be placed in a controlled temperature cabinet/chamber and
brought to the specified test temperature. Unless the core specimen temperature is
monitored in some manner and the actual temperature known, the core samples
shall remain in the cabinet/chamber for a minimum of 24 hours prior to testing at
41°F (5°C) and 77°F (25°C). Specimens shall be held at 104°F (40°C) for a
minimum of three hours, but not exceeding six hours prior to testing.
(a) Determine the tensile strength of the test specimens at 77° ~ 2°F using the
procedure described in Attachment A to SHRP Protocol P07.
(b) The test speciments) designated for resilient modulus testing shall be
brought to the first test temperature (41 ~ 2°F) as specified in section 7.! .
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The procedure described in section 7.1 shall be completed to bring the test
specimens to the remaining desired test temperatures (77 +2°F, 104
2°F).
7.2 Alignment anti Specimen Seating
At each temperature, position the test specimen so that the mid-th~ckness mark on
the test specimen is located in the line of action of the actuator shaft or alternately,
ascertain that the specimen is centered exactly between end markings on loading
strips. The diametral markings are then used to ensure that the specimen is aligned
from top to bottom and front to back. The alignment of the front face of the
specimen can be checked by ensuring that the diametral marking is centered on the
top and bottom loading strips. With the use of a mirror, the back face can be
similarly aligned.
The electronic measuring system shall be adjusted and gains set as necessary.
Prior to testing, zero the extensometers and the surface-mounted EVDT. An initial
negative offset might be necessary if high gain is being used andJor there is a
possibility of exceeding the range of voltage otherwise.
The contact surface between the specimen and each loading strip is critical for
proper test results. Any projections or depressions in the specimen to strip contact
surface which leave the strip in non-contact condition over a length of more than
0.75 inches after completion of load conditioning stage, shall be reason for rotating
the test axis or rejecting the specimen. If no suitable replacement specimen is
available, test shall be conducted on the available sample and the situation
documented.
Preconditioning
Preconditioning and testing shall be conducted while the specimen is located in a
temperature-controlled cabinet meeting the requirements of section 6.3.
7.3.1 Selection of the applied loads for preconditioning and testing at the three
temperatures is based on the indirect tensile strength, determined as
specified in Attachment A to the SHRP Protocol P07. Tensile stress levels
of 30, 15, and 4 percent of the tensile strength measured at 77°F are to be
used in conducting the test at temperatures of 41 ~ 2, 77 ~ 2, and 104
2°F, respectively. Specimen contact loads specified in section 1.5 (f) shall
be maintained during testing.
7.3.2 The sequence of resilient modulus testing shall consist of initial testing at
41°F, followed by intermediate testing at 77°F and final testing at 104°F.
The test specimens shall be brought to the specified temperature prior to
each test, in accordance to section 7. I. The computer generated waveform
shall be as closely matched as possible by adjusting the gains. The
number of load applications to be applied depend upon the test
temperature and the recommended number are 100, 100, and 50 for 41, 77,
and 104°F respectively. However, the minimum number of load
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7.4
7.5
applications for a given situation must be such that the resilient modulus
deformations are stable (section 7.5.~. When, using more preconditioning
cycles, the number of preconditioning cycles shall be recorded and the
reason documented. Also, if specimen has to be realigned, or when
preconditioning has to be stopped for any other reason, sufficient time
should be given to the specimen for relaxation before resuming the test.
Both the horizontal and vertical deformations shall be monitored during
preconditioning. If total cumulative vertical deformations greater than 0.015 inch
for 41°F, 0.03 inch for 77°F and 104°F occur, the applied load shall be reduced to
the minimum value possible and still retain adequate deformations for
measurement purposes. If use of smaller load levels are not adequate for
measurement purposes, discontinue preconditioning end generate 10 load pulses
for resilient modulus determination, and so indicate on the test report.
Testing
At the end of preconditioning at a specific test temperature, the resilient modulus
shall be conducted as specified below.
7.5.! Record measured deformation as specified in section 7.6 of this protocol
as soon as preconditioning is over (the load pulses are to be applied
continuously through preconditioning and data collection for resilient
modulus). Four of the last five cycles being utilized for resilient modulus
calculations shall be within ~ 5% of the average resilient modulus value.
7.5.2 After the specimenfs) have been tested at a specific test temperature, bring
the specimen to the next higher temperature in accordance with section 7.
and repeat section 7.3.2 through section 7.5. ~ of this protocol.
7.5.3 After testing is completed at 104°F, the specimen shall be brought to a
temperature of 77 ~ 2°F and an indirect tensile strength test conducted on
the test specimen as specified in Attachment A of SHOP P07.
Measure and record the recoverable horizontal and vertical deformations over the
last 5 loading cycles of the total applied load pulses. One loading cycle consists of
one load pulse and a subsequent rest period. The resilient modulus will be
calculated and reported for each cycle using the equations in section 9 of this
protocol. An average resilient modulus shall be obtained by calculating an average
of the resilient modulus values for the last 5 load cycles. If one or more individual
modulus value varies from the average by more than 15%, the value with the
greatest deviation shall be omitted from the average. If a second individual
modulus value varies by more than 15% from the average of the four remaining
values than the test shall be rerun. If the variation of individual modulus value is
less than ~ 5% from the average than the average of the four remaining values shall
be reported. The variation from the average is calculated as follows:
% Variation = ((MRi-MRa)/MRa)100
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where
MR; = InJiV;JUa! resilient modulus value, and
MRa = Average resilient modulus value.
7.7 Additionally, the cumulative horizontal and vertical deformation shall be
determined as per Attachment C of the S`IRP P07 Protocol.
8. QUALITY ASSURANCE/QUALITY CONTROL
8.! Prior to the start of resilient modulus testing each week, the laboratory testing
personnel shall perform testing on one or more of in-house QA/QC specimens
(L`ucite, Polyethylene and Teflon) specimens to verify the system response for
each test temperature to be used during the week. The synthetic specimens shall
be tested at a temperature of 77°F, at one rest period (0.9 sec.) on one axis and at
three load levels. The synthetic specimens for weekly QA/QC have been selected
to provide a response similar to the expected asphalt concrete specimen response at
a given temperature as follows:
- response similar to asphalt concrete testing at 41 °F
Polyethylene - response similar to asphalt concrete testing at 77°F
Teflon
- response similar to asphalt concrete testing at 104°F
If AC resilient modulus testing is to be performed at all three temperatures In a
given week, then all three samples shall be tested. If testing is to be conducted
only at 41°F for that week, then the Lucite specimen shall be tested at 77°F to
verify system response. If testing is to be conducted only at 77°F that week, then
the Polyethylene specimen shall be tested at 77°F to verify system response. And,
if testing is to be conducted only at 1 04°F that week then the Teflon specimen shall
be tested at 77°F to verify system response.
However, QAJQC testing shall be done whenever alignment of the loading system
may have changed.
The specimens shall be tested as follows:
Sail.! The specimen shall be located in a temperature-controlled cabinet meeting
the requirements of section 5.3 and at a temperature of 77°F. The applied
loads for preconditioning and testing for the synthetic specimens are
defined below:
S.~.2 The test specimen shall be preconditioned along the proper axis prior to
testing by applying a minimum of 30 cycles of the specified haversine-
shaped load pulse of 0. ~ second duration with a rest period of 0.9 second.
Load level 2 specified for the synthetic specimens in section 8.! .! will be
used for preconditioning. The computer generated wave form shall be
matched as closely as possible by adjusting gains and preconditioning
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shall continue until the horizontal deformations are stable and appear to be
uniform.
S.~.3 For each synthetic material, apply a minimum of 30 load pulses (each 0.1
second load pulse has a rest period of 0.9 seconds) and record measured
deformations as specified in section 7.6 of this protocol.
Perform the QA/QC testing by preconditioning a synthetic specimen at
load level 2, and then testing at levels 1, 2, and 3 respectively. To verify
the system response the deformation values shall fall within prescribed
limits that will be set by testing across various well-equipped laboratories
across the country.
S.2 The results from the QA/QC testing shall be stored as a permanent record of the
system response to obtain the system fingerprint. If all the synthetic specimens
have not been tested for each set of 100 resilient modulus tests, QA/QC testing
shall be performed on the remaining synthetic specimens in order to verify the
system response.
9. CALCULATIONS
The following equations are intended for the calculation of either instantaneous or total
values depending upon whether instantaneous or total deformation values are used.
Consider horizontal deformation as positive and vertical deformation as negative The load
value is assumed to be positive.
9.!
where,
it=
~v=
~. _
Poisson's ratio:
Poisson's ratio shall be calculated from the vertical and horizontal deformation
values by the use of the following equation:
1.9345-O.2699-
~ =. ah
0.4309+ V
ah
instantaneous or total Poisson's ratio,
the recoverable vertical deformation measured over a gage length equal to
three quarters of the diameter of the specimen, inches, and
the recoverable horizontal deformation measured over the horizontal
diameter ofthe specimen, inches.
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The calculated Poisson's ratio shall be subject to the following ranges:
4 ~ °F: 0. ~ -0.3
77°F: 0.25-0.45
104°F: 0.4-0.5
The upper or lower limits may be used for resilient modulus calculation, depending
upon whether the calculated Poisson's was greater than the upper limit or tower
than the lower limit, respectively. However, when in doubt about the validity of
the calculated Poisson's ratio, the calculated values shall be reported but the
following values shad! be assumed for purposes of resilient modulus calculation:
41°F: 0.2
77°F: 0.35
104°F: 0.5
When the calculated Poisson's ratio is outside of the ranges defined above, the
calculated values shall be reported and a visual inspection of the specimen should
be made to study the deformation in shape and/or presence of cracks due to
damage, and so reported.
When the resilient modulus test is being done to evaluate the deterioration in
condition of the pavement, initial values of calculated Poisson's ratio (at the
beginning of pavement life), if available, shall be used for resilient modulus
calculations. In case of unavailability, assumed Poisson's ratios as defined above
shall be used. However, Poisson's ratio shall also be calculated, and can be
compared to give another estimate of the deterioration or damage.
9.2 Resilient modulus:
The resilient modulus can then be calculated from the Poisson's ratio, as obtained
from section 9.l, and the recoverable horizontal deformation (instantaneous or
total) according to the following equation.
P
MR= (0.2699+~)
Act
where,
MR =
instantaneous or total resilient modulus, psi,
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ah - recoverable horizontal deformation, inches,
thickness of the specimen, inches,
Pcyclic = PmaX- Pcontact
.
cyclic load applied to the specimen, Ibs.,
Pmax = maximum applied load, Ibs.
Pcontac~- contact load, Ibs., and
11 =
10. REPORT
instantaneous or total Poisson's ratio.
10.! The following general information shall be recorded:
10.~.! Sample Identification.
10.~.2 Average thickness of the test specimen (t), to the nearest 0.01 inch (as per
section 6.4~.
10.13 Average diameter of the test specimen (D), to the nearest 0.01 inch (as per
section 6.5~.
10.~.4 Indirect tensile strength (initial), to the nearest psi.; from a comparable test
specimen used to select the stress (or load) level for the testing.
10.~.5 Indirect tensile strength (final), to the nearest psi; for the test specimen
after the resilient modulus test has been completed.
10.~.6 Comments: The following (and additional, if so required) comments
should be recorded, when relevant.
(a)
(b)
(c)
If sawing was required for core specimens.
If the specimen was skewed (either end of the specimen departed
from perpendicularity to the axis by more than 0.5 degrees or I/8
inch in 12 inches), as observed by placing the specimen on a level
surface and measuring the departure from perpendicularity.
If a "dummy" specimen was used to monitor the temperature. If
not, the time specimen was maintained at the test temperature in
the environmental chamber.
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(~) If tests could not be completed at all temperatures due to
damage/failure of test specimen.
(e)
If the projections/depressions on the test surface were higher or
deeper than 1/16 inch and the specimen was tested as no
replacement specimen was available. Record the
projections/depressions in such a case.
If for core specimens, no traffic direction was marked, or if test
was not performed on the marked axis due to some reason.
10.2 The following information shall be recorded at each test temperature:
10.2.! Instantaneous Resilient Modulus:
(a) The vertical load levels (Pcyc~ic)
(b) The contact load (PContact) used over the last 5 loading cycles for
each test temperature.
(c) Instantaneous recoverable horizontal and vertical deformations
measured over the last five cycles.
(~) The calculated instantaneous Poisson's ratio (pi) over the last S
loading cycles for each test temperature.
(0
The calculated instantaneous resilient modulus (Mu) over the last
5 loading cycles for each test temperature.
The average calculated instantaneous Poisson's ratio and
instantaneous resilient modulus for the last 5 load cycles and
standard deviation calculated at each test temperature. If any one
modulus value varies from the average by more than 15%, it shall
be omitted from the average calculation. However, all five values
shall be reported and those not included in the average should be
noted in the general remarks.
10.2.2 TotaIResilient Modulus:
(a) The vertical load levels (PCyc~ic).
(b) The contact toad (PCon~ac') used over the last 5 loading cycles for
each test temperature.
(c) Total recoverable horizontal and vertical deformations measured
over the last five cycles.
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(d)
The calculated total Poisson's ratio (I over the last 5 loading
cycles for each test temperature.
The calculated total resilient modulus (Ma) over the last 5 loading
cycles for each test temperature.
The average calculated total Poisson's ratio and total resilient
modulus for the last 5 load cycles and standard deviation
calculated at each test temperature. If any one modulus value
varies from the average by more than 15%, it shall be omitted
from the average calculation. However, all five values shall be
reported and those not included in the average should be noted in
the general remarks.
10.23 Permanent Horizontal and Vertical Deformations:
(a)
The number of preconditioning cycles used for each test
temperature.
(b) The cumulative permanent vertical deformation measured,
including the preconditioning cumulative deformation and the
resilient modulus testing cumulative deformation.
(d)
(g)
(h)
The cumulative permanent horizontal deformation measured,
including the preconditioning cumulative deformation and the
resilient modulus testing cumulative deformation.
The total number of load cycles conducted during the test. This
includes the number of cycles for preconditioning and those
cycles conducted for the determination of resilient modulus.
The cumulative vertical deformation measured after
preconditioning prior to initiation of resilient modulus testing.
The cumulative horizontal deformation measured after
preconditioning prior to initiation of resilient modulus testing.
The cumulative permanent vertical deformation per load cycle.
The cumulative permanent horizontal deformation per load cycle.
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Representative terms from entire chapter:
test specimen
