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OCR for page 295
1X A
i I~I HEM ~ NATIONS
~R LEA ~LCI1ON
A-1
OCR for page 296
APPENDIX A
DIAMETRAL TEST EQUIPMENT AND EQUATIONS FOR DATA REDUCTION
DIAMETRAL TEST DEVICES
This section gives a detailed description of the different diametral test devices used in Me study
to evaluate the resilient modulus of asphalt concrete. Bow the construction of the equipment and its
operation are described.
Retsina Device.
The Retsina device is We most simple device studied. This device uses a fixed bottom loading
strip with an independent loading strip that is placed on the top of the specimen. The load is transferred
through a small (0.5 in. diameter) metal ball which rests on an inverted conical groove on the top of Me
upper loading strip (Figure Add. For this device to work properly, the loading plane should be perfectly
aligned with the vertical diametral plane of the specimen, and the loading system should be very
accurately aligned. Due to the absence of a rigid connection between the loading strip and the load cell,
or Me loading system which applies load through He ball, a tendency exists for separation of Me loading
system (ram) from the loading strip. Also, there is a tendency for the upper loading strip to move during
testing.
Since there is no room on the upper loading strip to measure the deformation using a spring-
loaded EVDT, the vertical deformation of the MTS ram was used to calculate resilient modulus.
Deflections in the horizontal diametral plane were measured using both mountable and stand-alone
measurement devices (extensometers and EVDTs). EVDTs were attached to the side walls of the bottom
portion of the MTS device which acted as the fixed bottom loading strip. A high degree of freedom
exists in the Retsina device, and hence it is more liable to equipment and operator errors. This fixture
can be easily used in many standard environmental chambers without modifications.
M7S Device.
An MTS Mode! 643.01A Resilient Modulus Fixture was also used in this study (Figure A-21.
The fixture can be installed in a load unit having either a crosshead or a baseplate mounted actuator. It
is small and simple enough to be used in many small environmental chambers. The MTS device has
upper and lower platens goading plates). A pulfrod (ram) connects the upper platen to the load cell. To
insure Mat the longitudinal center line of the loading strips remain in the vertical diametral plane of the
test specimen throughout the testing, an alignment bar is connected to one side of the upper loading
platen. This alignment bar is guided between tow cam rollers mounted on the side plate of Me lower
loading platen hence preventing the rotation of Me upper plate in a horizontal plane. The specimen seats
between He loading strips attached to the upper and lower loading platen. Different loading strips are
used for 4 in. and 6 in. diameter specimens.
The deformations are measured by extensometer assemblies supplied by MTS. A vertical
extensometer can be mounted between the upper and lower platen on one side wall of He lower platen
(wall opposite to the one with the alignment bar and cam rollers). A horizontal extensometer assembly
can be mounted on He specimen to measure horizontal deformation. The assembly consists of two
extensometers held by springs against He sides of the specimen. Two slots are provided in each side wall
of He lower platen to help mount the extensometers on to the specimen. Four thumbscrews are provided
with He device (Figure Add. These hold the extensometer assembly in place while a new specimen is
A-2
OCR for page 297
Figure A-lb.
LOAD
sea BAR L
UPPER LOADING
~ STRIP PLACED ON
INS Mu CONIC ~ SPECIMEN
GROOVE ~I -
~- 1
1
\
\~ SPECIE
I . ~
-7
, ,
=~/BOTTOM LOADING
~ jet S1 RIP AND PLATE
T. ~
Figure A-la.
Sehcmatic view of the Retsina device
Retsina device test setup at NCSU with Extensometers
A-3
OCR for page 298
RAM
SPECIMEN
. . . - . ~
VERTICAL DISH ~J\
[ATERAL DEFOR~ON ~ ~ ~
EXTENSOM=F~.RY.~ ~ ~-~ i
~ ~ ~ ~7 Jl
SPECIMEN LOADING
STRIPS
/
/
LOWER PENSION ROD
:111
·1<
/
LOW FRICTION
ANTI-ROTATE FUTURE
. ~
it.
EXTFNSOME I OR AND SPECIMEN
ALIGNMENT FIXTURE
Figure A-2. Schematic view of the MTS Resilient Modulus Fixture with an installed
specimen
A-4
OCR for page 299
a a
- ~
screw in
En.} 1
i
r 1 storage
0 0 0 (, ~
front view
assembly
pulled away
ED
ton view
Figure A-3. Using the Thumbscrews on the MTS device (installation arid removal of
the specimen)
r ~
AT
~ ,~,n
install,
center on loading strip
41_
roll gently
against bracket
1. 1 -- ' ' -~l
_ It,tillll~ylU~tl j At, jar, \
Q~ ~n
- 1 _ ~
I ~' 1t
-
=
Figure A-4. Aligning the specimen in the MTS device
A-5
OCR for page 300
put in or replaced. The specimen can be rocked in the lower platen to make sure that it has full contact
with the extensometer assembly and hence ascertaining the longitudinal alignment of the specimen with
the loading strips (Figure And. Once Mat is accomplished, the thumbscrews are unscrewed which pulls
the extensometer assembly on to the specimen in the horizontal diametral plane.
To facilitate the simultaneous use of the stand-alone and mountable measurement devices for
horizontal deformation, holes were drilled in Be side plates to mount spring-Ioaded EVDTs. Also, long
arm attachments were designed and fabricated to hold vertical EVDTs (that could be spring-Ioaded on
the top of the upper platen on opposite sides of the ram). These were fixed to the base of the side walls
of the lower platens with a rotating arm on the top which held the EVDTs. The same attachment was
used for the SHRP EG device setup for the measurement of vertical deformation.
A marking device (described later) was developed to accurately mark mutually perpendicular axes
on both faces of the specimen with precision. The specimens were then aligned between We loading
strips and the extensometer assembly using He marked axes as datum. This was generally observed to
provide a good control on rocking. Very thin lines were precisely drawn at the ends of the loading strips
to facilitate alignment of the specimen. However, it should be ensured that the loading system is
perfectly aligned to minimize rocking. The alignment of the MTS loading system was periodically
checked.
A very short Hence smaller weight) ram attached to the upper loading platen was used in one
experiment to determine if a significant difference existed in the control of rocking compared to a long,
heavy ram.
The MTS device is simple in design. The upper loading platen is thinner than those used in the
Baladi and SHRP devices. However, only the MTS device is rigidly connected to the loading system.
A little control over the rotation of the upper platen is provided by the presence of an alignment bar and
cam rollers, but careful alignment of the loading system is still required. Due to the absence of heavy
guide columns, friction is not a major concern to the movement of the device in either the transverse or
the vertical direction. The absence of resistance to the movement in the transverse direction might be
considered as a drawback of the device. However, absence of resistance friction in the vertical direction
ensures that the load cell measures the full load applied to the specimen. The MTS device is open enough
to be adaptable to different measurement systems, a flexibithe SHRP EG and Baladi~s device.
Baladi's Device.
The Baladi device used in this study was supplied by the Gilson Company, Inc. (Ohio) as mode}
MS 40 (Figure A-51. This device can only be loaded from the top. The Baladi device consists mainly
of a fixed top and bottom cylindrical assembly supported by four columns, two on the side and one each
in the front and back of the specimen (when installed). Holes are drilled in these columns so that the
deformations can be obtained by use of EVDTs mounted through them. A short attachment is made on
the fixed upper part of the device to obtain measurements in the vertical direction with a EVDT mounted
through it. The Baladi device is the only one to permit deformation measurements in three dimensions.
The upper part has five holes, one for the loading piston and four for the low friction guide posts, and
through which the upper plate moves. The load is applied through a standard ~ in. diameter steel ball
that rests on the upper loading plate in an inverted conical groove on the center. The Baladi device, in
contrast to the others, has a hinged upper loading strip so as to accommodate a nonuniform diameter
specimen. The device is compact, and hence it is very cumbersome to put the extensometer assembly
on the specimen. Also, the installation of the specimen is not easy, although a rubber stopper is provided
at the top to assist in the installation of specimen. centerlines were marked on the end of the loading
A-6
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LOAD
STANDARD 1.
STEEL BALL
UNBAR MORON
BUSHING
1
LOADING PISTON '
or
11 1 \
11 I Let
for
r LOADING PISTON
I GUIDE PLANE
-___' r- ~ I
l l r GUIDE POST
. .~ .
UPPER STATIONARY
_ PILATE ,7
ll
f'
BEARING
RETAINER
CUP -
UPPER LOADING-
S1RIP, HINGED
~ !1_ ~ a---~
~ T___d I r-~
\
L
. ~
\ _1_
. ~1
cot--~ ! ·! I
. . 11 :
r ~
\
. ,
L
TEST
SPECIMEN
1 1
1 \
BOrrOM LOADING
STRIP, FIXED
Figure A-S. Schematic view of Baladi's device
A-7
POST, LVDT
! HOMER
- LO\VER STATIONARY
PLATE
OCR for page 302
strips to help in the alignment of the specimens. Friction in the vertical direction generated by the use
of four guide posts, reducing the load applied to the specimen, is a concern. To overcome this problem,
a load cell can be place between the lower curved loading strip and the lower stationary plate [171.
SHRP Load Guide (ZG) Device.
The SHRP EG device was developed as a part of the Strategic Highway Research Program's
Long-Term Pavement Performance project (Figure Add. The device has to be used under a top loading
system. The device is a die set with upper and lower loading platens constrained to remain parallel
during testing by the presence of two heavy guide posts. The guide posts are in line with the loading
strips hence assuring minimal lateral movement of the top loading strip with reference to the lower. the
lading platens are very heavy and rigid. The loading system is connected to the device with a complex
arrangement using a metal ball and springs between two flanges (Figure Ado. The loading system is
a compromise between the very rigid connection used in the MTS device and a free connection used in
Baladi's device. A counterweight system prevents the heavy weight of the loading system from being
applied to the specimen (which is very critical at high temperatures).
Two standoffhor~zontal transducer holders are attached to the lower platen of the load frame such
that the EVDTs can be positioned at the mid height of the specimen on either side. The holders are
movable by a fine screw adjustment that makes it very easy to zero the EVDTs prior to testing. Stee!
loading strips. curved to a diameter of a 4 in. specimen are fixer! to the Platens. The outer edges of
, ~ . · ~ · . . e _ ~ ~
these strips are rounuecl to remove Sharp edges mat might cut specimens during testing. l he LVL) 1 S and
the extensometers cannot be used simultaneously for He measurement of horizontal deformation.
Therefore, two sets of tests had to be performed to evaluate these measurement systems wig the SHRP
device.
The bulky guide columns and the counterbalance systems could be a source of appreciable friction
to the vertical movement and causing a lower load to be applied to the specimen. Due to the size of the
device and counterbalance system, the device cannot be conveniently used within a conventional
environmental chamber. Also, the loading strips are not easily removable, and hence it would be
difficult, but not impossible, to test 6 in. diameter specimens in in the device is cumbersome and requires
a significant amount of time and patience to obtain proper alignment.
Some modifications have been made by SHRP personnel to the SHRP EG device since its use on
this project. The loading strips have been changed and the transducer standoff devices have been
modified to account for the thicker loading strips now used. The thinner load strips formerly used were
provided less contact area and were believer to be deforming due to a pre-existing deformation in the
upper platen. The SHRP personnel also suggested mounting the EVDTs directly on to He top of He
upper loading strip by drilling a hole through the upper loading platen or to use snap-in spring-Ioaded
EVDTs between He loading strips (while using a stop collar on the guide posts to avoid damaging the
EVDTs during testing).
Marking Devices
The device used to accurately mark diametral specimens is described in detail in this section. The
device has two parallel metal plates wig windows to facilitate the marking of axes through them. These
metal plates are connected by steel rods through He bottom. The metal plates can be slid over these rods
so as to adjust to any Sickness of the specimen. A marking tool, which is essentially a long steel bar
plate rod, etc., with a tapered edge, is used to etch a thin line on the sample surface. A hinged plexi-
glass window is provided wig horizontal lines etched on it. The horizontal lines are precision-etched so
A-8
OCR for page 303
Cl
c:
\
in
o
:,
ME
1
~ -
c)
·5
· _
V
A-9
:r
UJ
G
G
n
o
VO
·
3
as
en
U]
a'
it_
o
3
·5
Cat
._
U]
set
AS
._
OCR for page 304
~ 1
Figure A-7. SHRP LO Device setup at NCSU with a synthetic specimen
A-10
OCR for page 305
as to be perfectly perpendicular to the marking edge in the window of Me front plate. The plexi-glass
window can be rotated in the horizontal plane and locked in one the front plate. In an unlocked position
it can be moved up and down. If it is required to mark axes at different angles (other Wan 90°), lines
should be etched on Me window at the required angle.
The marking of the axes on a specimen using this device is accomplished by Me following steps:
The specimen is cradled between the connecting rods near the front plate so that it sits
comfortably. Rocking tendency is checked by applying light pressure near the approximate
vertical diametral plane on the top of the specimen near the front and back faces.
2. The back plate is Men brought close to the specimen and screwed in place.
3. The specimen is rotated again to ensure that it sits correctly between the two plates. Small light
lines are marked at the front and the back near the center of Me specimen.
4. Rotate (approx. 120° or less) Me specimen and repeat the above step. Once at least three lines
are marked, check Me specimen faces to see that they pass through a corrunon point. If the
specimen is not of uniform diameter or was not seated properly, the liens will form a polygon.
In Me first case, determine Me approximate center of Me polygon. For Me later case, repeat Me
procedure again.
J
Once Me center is determined for both faces, cradle Me specimen correctly between Me rods wig
Me plates as close to Me specimen as possible. Then mark the diametral axis on Me front and
back of Me specimen (without moving the specimen) making sure Mat it passes Trough the center
points.
6.
Rotate Me specimen and rotate the plexi-glass window about its hinge so that it locks into place
on Me front plate, one of Me lines coinciding with Me center of Me specimen. Rotate the
specimen so Mat Me first diametral axis coincides completely wig Me etched line on Me plexi-
glass window.
7. Unlock Me window carefully so as net to disturb Me specimen and mark diametral axes on Me
front and Me back.
This marking device, along wig lines etched on the center of Me loading strips, helps in reducing rocking
and making the alignment of Me specimen much easier.
Indirect Tension Test Analysis Methods
AS7M Analyst
Lois analysis is from Me ASTM D 4123-82 procedure for Me resilient modulus testing of asphalt
cohere. Absolute vadues of all deformations are to be Ken for He purpose of His analysis. Poisson's ratio
(m) and resilient modulus (MR) are determined by Me following two equations:
p=359g,~ -02~7
my
t8,
A-11
(1)
(2,
OCR for page 306
where,
P = applied repetitive load
t = Sickness of the specimen
ME = resilient modulus, and
m = resilient Poisson's ratio
dx,dy = measured deformations in Me x and y axis, respectively.
According to ASTM D4123-82, a Poisson's ratio of 0.35 can be assumed, if n~;sary, at a temperature of
77 F. The above equations can be used ~ calculate Me instantaneous or Me gal Poisson ratio and resilient
modulus depending upon whether instantaneous or total deformation is used.
Elastic Analysis.
The elastic analysis method was developed during this study and is based on an assumption of
linear elastic behavior of a statically loaded specimen. The following equations were developed for Me
strains along the tic and y axes from the stress equations given by Hondros [A-21:
4P
£X =
{MR7C
-4P
~ {MR7C I
where,
(1 X ) · 2a
_-
+ 2-cos2a +
R2 R4
X4 (F 1)~ (R: + z teals)
(I + lo) ~ ~ (l - Stan ( R 7 - Ye )
ex, e', = strains along the ~ and y axes, respectively
(3)
(4)
2a = angle subtended at the specimen center by Me loading strip
R = radium of the specimen
x, y = distances along the x and y axes, respectively
P = applied repetitive load
A-12
OCR for page 307
thickness of the specimen
MR =
m
resilient modulus, and
resilient Poisson's ratio
By integrating these equations from -~/2 to L/2, where ~ is the gage length for Me mounted EVDT, We
deformation over a gage length of ~ (symmetric over the center) can be found. The equations given
below are only valid for 4 in. diameter specimens loaded with a 0.5 in. wide rigid loading strip. The
equations derived for a 4 in. diameter specimen are also valid for a 6 in. diameter specimen loaded by
a 0.75 in. wide loading strip, provided the ratio of gage length to specimen diameter is the same. For
example, the equations derived for a 1 in. gage length on a 4 in. diameter specimen are valid for a I.5
in. gage length on a 6 in. diameter specimen. For Me purpose of this analysis, horizontal (tensile)
deformation is considered positive, while vertical (compressive) deformation is considered negative.
Equal gage lengths along the two ax" - - Integrating Equations (3) and (4) over a gage length of C,
the deformation in the tic and y directions and, respectively, is obtained:
AL = M ~ (a + tell)
at = M , (C + by)
(5)
(6)
where aJb,c, and d are constants given in Table A-1, dependent on Me gage length L (refer to Table A
1). .
Table A-1. Values of constants a,b,c, and ~ in the elastic analysis for different gage lengths
on a 4 in. diameter specimen
Gage Length | Constants
L (ins) a
. .
1 0.1444 0.4508 0.4886
2 0.2339 0.7801 1.0695
3 1 0.2699 1 1 1 3.5879
. -
d
0.1558
0.3074
.0627
A-13
OCR for page 308
Taking the ratio of vertical and horizontal deformation, is determined as follows:
~yL
-c-a
.. =-
~ L
d+b A
(7)
The resilient modulus can then be determined by using Equation (3) for horizontal deformation.
Equation (5) can then be solved ~ obtain the resilient modulus. Equation (5) when solved for resilient
modulus and Equation (7) closely resemble We analogous equations for resilient modulus given in ASTM
D 4123-82.
Different gage lengths along the two axes - - The following equations were derived for the analysis of
tests on 4 in. and 6 in. diameter specimens with a gage length to diameter ratio of 3/4 and ~ for vertical
and horizontal deformation, respectively. Equation (2) was integrated over a gage length of 3 in. for the
4 in. diameter specimen (or 4.5 in. for a 6 in. diameter specimen) to obtain
6) ,3 ~ ~ M ~ (19345 + 0.430911)
To determine Poisson ratio, a ratio of Me vertical deformation given by Equation (6) to Me horizontal
deformation for a 4 in. gage length, given in Equation (5) was taken to obtain
- I.9345 - 0~699 Y
6)r4
-0.4309+ Y
a)~4
(9)
The resilient modulus can Men be determined from Equation (5) using a gage length of 4 in. to measure
horizontal deformation.
SHRP PO? ALSO
The SHRUB P07 (November I, 1992) procedure uses Me following equations:
0.859- O.O8R
~ =
~0.2851t - 0.04
(IO)
In general, for different configurations of Me measurement system, Me venicalIhor~zon~ deformation
ratio R' can be defined as,
(1 l)
A-14
OCR for page 309
In He above equation VO us He vertical compliance favor. The use of a compliance factor VO would
improve He value of Be vertical deformation for He purpose of He calculation of Poisson's ratio. However,
a compliance factor will have to be de=Tnined for each different test setup.
The SHRP procedure limits Poisson's ratio to a range of 0. ~ to 0.5, even when He circular values
go outside these bounds. For He purpose of comparison with over methods ~ this project, He value of
Poisson's ratio was not array changed, even when it was out of He specified range.
The resilient modulus Is Hen calculated accords to the following equation
PD(O.08+0.297P ~0.0425[12)
MR=- tH
where
(12)
H = ~ e recoverable ~nstar~taneous or total horizontal deformation, in.
(Absolute values of all deformations are to be taken for He purpose of Ads
analyses.),
applied repetitive load ,lbs.
~= sample thickness, in.
D =
ROqUe and Busier) A,~S`S
Roque and Buttiar (A-3) proposM an analysis system for He Gage~o~nt-mount~ system of
measuremerK. It only applies for a gage length to diameter ratio of I:4 and when He height of He surface
mounted EVDT Is 0.25 in. from He specimen surf. Horizontal ( - site) deformation is considerM to be
positive, while vertical (compressive) deformation is considered to be negative for this analysis. A stq~by~tep
procedure for Ads analysis Is described below:
sample diameter, in.
t. Assume Poisson's ratio, m (for example, assume 0.35 at 77 E9.
2. Correct horizontal deformation (to ~ far bulging)
H = (~.0 ~-0.12 p-0.O: ~-): HM
where,
=
= measured specimen Lichens
~=
H -
M ~
standard specimen Richness (2.5 in. for 4 in. diameter specimen)
measured horizontal deformation
A-15
(13)
OCR for page 310
5.
Correct vertical deformation (to account for bulged
Y = (O .994 - O . 128~) $ Y.,'
where YM is He measured vertical deformation.
4. Horizontal point swain at the center of speck s given by,
Achy = ~ 07 Gil,
and He vertical point strain at die center of specimen is given by,
y
£ CT3? = 0 98 GL,
where,
~=
H -
-
gage length, in.
horizontal deformation, in.
Y = vertical deformation, in.
5. Corrupts horizontal point stress at He center of specimen
~ = 0.! 859-
SCOUR t,~
Corrected vertical point stress at He center of specimen
Or =~.4636
COM
(14)
(15)
(16)
(1~
(18)
(Note: Lee factors used in Equations (17) and (18) were obtained Tom Table I in Roque and Buttiar's
paper and are only valid for a Richness to diameter ratio of 0.625 for He specimen and a Poisson
ratio of 0.35)
A-16
OCR for page 311
6. Capable Po~n's ratio use
(£CTRX ~
XCOM ~ ~ ) YCOM
C7Rr
£CTR,`
(S YCOM ~ ~ ECrR, , IS XCOM
(19)
If Poisson's ratio calculated In Step 6 differs by more Man 0.01 win Poisson ratio In Step ~ Men
replace m in Step ~ by Me value calculated In Step 6 arm repeat Steps 2 - 6, else go on to the next
stop.
7. The asphalt concrete modulus can Men be determined by,
M * = (~ x
~ C TRY CON* rCO'R
Notation Used In Experiments
(20)
A standard set of notations is described below which is used in presenting Me diametral test
experimental findings. Additional notation employed is described where it appears.
Value of Resilient Modulus and Poisson's Ratio
Notation Used
pr:
mr:
1:
EXSUM and GPM Alignment System
Variable Presented
Poisson's ratio
Resilient modulus
This letter is used as a suffix to the resilient modulus (mr) and
Poisson's ratio (pr) notations given above if the value is
calculated from the instantaneous values of recoverable
deformation. Otherwise, the values of pr and mr were calculatM
from the total recoverable deformation.
A precision L~VDT alignment system was used in both Me gag~point-mounted (GPM) and the
general EXSUM deflection measurement method. This alignment system and its installation is described
here.
Device Description'
The device has two brass arms fitted perpendicular to each other. The arms are made using
channel selections and have grooves in them in which small mounting blocks can be positionM. Along
A-17
OCR for page 312
the length of Be arm, small holes are precision~rilled on Me side such ~at, when screws are put through
them to hold the mounting blocks tight in the groove, the correct gage length is maintained between the
glue points on the mounting blocks. Holes are drilled at regular intervals to define gage lengths from
in. to 6 in. at a 0.5 in. interval.
Support legs can be slid over the four ends of the brass arms to support the alignment device in
place over the specimen while the glue sets. Lines are etched on He inside of the support legs which
should coincide with the marked diametral axes. This design insures that the mounting blocks and the
EVDT (Note: two EVDTs are used in the GEM setup) are in perfect alignment with the diametral axis.
Setup of the EXSUM System
The procedure for the setup of the EXSUM deformation measurement system on a diametral test
specimen is as follows:
7.
Just before testing, He diametral axes are marked on a specimen. Unless there is a
requirement to perform testing along a particular axes, select the axes so that the gage-points
are on the best side of the specimen and over relatively homogenous portions of He asphalt
concrete. mark the axes on the front and back of the specimen using the marking device.
Place the specimen on its side wig the top side being the one on which the EVDT is to be
mounted.
Position the alignment device, with He four support legs loosely slid over the ends, on the
specimen such Hat the lines marked on the four legs match the diametral axes. Now, tighten
the support legs in position.
Remove the alignment device by vertically lifting it over the sample. Lay it upside down so
Hat the channels of He brass arms are visible.
Take a pair of mounting blocks and loosely tighten the EVDT body in one and screw in the
EVDT core in the over. Position the mounting blocks in He groove (one by one) and hold
them tight along the bottom and the side opposite to the one having holes in the brass
channel.
Insert He screws from the side and tighten them in place. This ensures that the mounting
blocks, when glued, are perpendicular to the surface of the specimen.
Zero He EVDT by screwing in or out the EVDT core connecting rod. Invert the alignment
device and Den tighten He plastic screws so Hat the EVDT remains in the zero voltage
output position.
Next, uniformly mix the epoxy on a glass plate or other suitable surface. Apply the epoxy
at the gluing surfaces on the mounting blocks, and then carefully align the alignment device
such that the lines marked on the support legs match the diametral axes. Alignment should
be easy to accomplish since the legs have already been fixed on He brass arms in ache proper
positions. By aligning one or maybe two legs, all the four legs should be in position. Use
a flashlight, if required, to make sure that the axes match with the center lines on He legs.
Cure the epoxy at or above room temperature. Applying heat from a blower accelerates
curing. Tape the EVDT connecting wires to the specimen so that He weight of He
A-18
OCR for page 313
connecting wire does not pull down on the glued mounting block when the alignment
assembly is taken off.
10.
~-
References
A-t
A-2.
A-3.
Once the epoxy is hard enough (normally ~ to 10 hours), carefully loosen the screws holding
the legs and the mounting blocks. Remove the alignment device by lifting it vertically from
the surface of the specimen. Allow He specimen to cure for an additional 6 to ~ hours. The
total recommended time for curing is approximately 16 hours.
Mount the extensometer assembly on the specimen taking care that it does not touch the
mounted EVDT. The specimen is ready for testing after bringing it to the required
temperature in the environmental chamber.
Baladi, G.Y. and Harichandran, R.S. (1989), "Asphalt Mix Design and the Indirect Test: A
New Horizons, Asphalt Concrete Mix Design: Development of More Rational Approaches,
ASTM STP 1041, W. Gartner, Ir., Ed., American Society for Testing and Materials,
Philadelphia, PA.
Hondros, G. (1959), "The Evaluation of Poisson's Ratio and the Modulus of Materials of a
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OCR for page 314
Representative terms from entire chapter:
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