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Proposed Standard Practice for
Preparation of Cylindrical Performance Test
Specimens Using the Superpave Gyratory
Compactor
NCHRP 9-29: PP 01
1. SCOPE
1.1 This practice covers the use of a Superpave gyratory compactor to prepare 100 mm
diameter by 150 mm tall cylindrical test specimens for use in a variety of axial
compression and tension performance tests. This practice in intended for dense-,
gap-, and open-graded hot mix asphalt concrete mixtures with nominal maximum
aggregate sizes to 37.5 mm.
1.2 This standard may involve hazardous materials, operations, and equipment, This
standard does not purport to address all of the safety problems associated with its
use. It is the responsibility of the user of this procedure to establish appropriate
safety and health practices and to determine the applicability of regulatory
limitations prior to its use.
2. REFERENCED DOCUMENTS
2.1 AASHTO Standards
· T 312, Preparation and Determining the Density of Hot-Mix Asphalt (HMA)
Specimens by Means of the Superpave Gyratory Compactor.
· R 30, Mixture Conditioning of Hot-Mix Asphalt (HMA)
· T 166, Bulk Specific Gravity of Compacted Asphalt Mixtures Using Saturated
Surface-Dry Specimens.
· T 209, Theoretical Maximum Specific Gravity and Density of Bituminous Paving
Mixtures.
· T 269, Percent Air Voids in Compacted Dense and Open Bituminous Paving
Mixtures.
2.1.1 ASTM Standards
· D 3549, Thickness or Height of Compacted Bituminous Paving Mixture
Specimens.
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3. TERMINOLOGY
3.1 Gyratory Specimen Nominal 150 mm diameter by 170 mm high cylindrical
specimen prepared in a Gyratory compactor meeting the requirements of AASHTO
T 312.
3.2 Test Specimen Nominal 100 mm diameter by 150 mm high cylindrical specimen
that is sawed and cored from the gyratory specimen.
3. 3 End Perpendicularity - The degree to which an end surface departs from being
perpendicular to the axis of the cylindrical test specimen. This is measured using a
combination square with the blade touching the cylinder parallel to its axis, and the
head touching the highest point on the end of the cylinder. The distance between the
head of the square and the lowest point on the end of the cylinder is measured with
feeler gauges.
3.4 End Planeness Maximum departure of the specimen end from a plane. This is
measured using a straight edge and feeler gauges.
4. SUMMARY OF PRACTICE
4.1 This practice presents methods for preparing 100 mm diameter by 150 mm tall
cylindrical test specimens for use in a variety of axial compression and tension
performance tests.
5. SIGNIFICANCE AND USE
5.1 This practice should be used to prepare specimens for the following standard tests:
· AASHTO TP 62, Determining Dynamic Modulus of Hot-Mix Asphalt Concrete
Mixtures
· NCHRP 9-29 PP 03, Determining the Dynamic Modulus and Flow Number for
Hot-Mix Asphalt (HMA) Using the Simple Performance Test System
5.2 This practice may also be used to prepare specimens for other non-standard tests
requiring 100 mm diameter by 150 mm tall cylindrical test specimens.
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6. APPARATUS
6.1 Superpave Gyratory Compactor - A compactor meeting the requirements of
AASHTO T 312 and capable of preparing finished 150 mm diameter specimens that
a minimum of 170 mm tall.
Note 1 - Research completed to date has not determined if it is critical that the
compactor maintain the internal angle specified in AASHTO T 312 when compacting
170 mm tall specimens. Until additional work is completed compactors meeting
either the external or internal angle requirements of AASHTO T 312 may be used.
6.2 Mixture Preparation Equipment Balances, ovens, thermometers, mixer, pans, and
other miscellaneous equipment needed to prepare gyratory specimens in accordance
with AASHTO T 312 and make specific gravity measurements in accordance with
AASHTO T 166, T 209, and T 269.
6.3 Core Drill An air or water cooled diamond bit core drill capable of cutting nominal
100 mm diameter cores meeting the dimensional requirements of Section 9.5.3. The
core drill shall be equipped with a fixture for holding 150 mm diameter gyratory
specimens.
Note 2 Core drills with fixed and adjustable rotational speed have been
successfully used to prepare specimens meeting the dimensional tolerances given in
Section 9.5.3. Rotational speeds from 450 750 RPM have been used.
Note 3 Core drills with automatic and manual feed rate control have been
successfully used to prepare specimens meeting the dimensional tolerances given in
Section 9.5.3.
6.4 Masonry Saw An air or water cooled diamond bladed masonry saw capable of
cutting specimens to a nominal length of 150 mm and meeting the tolerances for end
perpendicularity and end flatness given in Section 9.5.3.
Note 4 Single and double bladed saws have been successfully used to prepare
specimens meeting the dimensional tolerances given in Section 9.5.3. Both types of
saws require a fixture to securely hold the specimen during sawing, and control of the
feed rate.
Note 5 In National Cooperative Highway Research Project 9-29, a machine that
performs both the sawing and coring operation within the tolerances specified in
Section 9.5.3 was developed. Contact: Shedworks, Inc., 2151 Harvey Mitchell
Parkway, S., Suite 320, College Station, TX 77840-5244, Phone (979) 695-8416, Fax
695-9629, email wwc@shedworks.com.
6.5 Square Combination square with a 300 mm blade and 100 mm head.
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6.6 Feeler Gauges Tapered leaf feeler gauges in 0.05 mm increments.
6.7 Metal Ruler Metal ruler capable of measuring nominal 150 mm long specimens to
the nearest 1 mm.
6.8 Calipers Calipers capable of measuring nominal 100 mm diameter specimens to the
nearest 0.1 mm.
7. HAZARDS
7.1 This practice and associated standards involve handling of hot asphalt binder,
aggregates and asphalt mixtures, and the use of sawing and coring machinery. Use
standard safety precautions, equipment, and clothing when handling hot materials and
operating machinery.
8. STANDARDIZATION
8.1 Items associated with this practice that require calibration are included in the
AASHTO Standards referenced in Section 2. Refer to the pertinent section of the
referenced standards for information concerning calibration.
9. PROCEDURE
9.1 HMA Mixture Preparation
9.1.1 Prepare HMA mixture for each test specimen and a companion maximum specific
gravity test in accordance with Section 8 of AASHTO T 312.
9.1.2 The mass of mixture needed for each specimen will depend on the gyratory specimen
height, the specific gravity of the aggregate, the nominal maximum aggregate size
and gradation (coarse or fine), and the target air void content for the test specimens.
Appendix A describes a trial and error procedure developed in NCHRP Project 9-19
for determining the mass of mixture required to reach a specified test specimen target
air void content for gyratory specimens prepared to a height of 170 mm.
Note 6 Test specimens with acceptable properties have been prepared from
gyratory specimens ranging in height from 165 to 175 mm. The height of the
gyratory specimen that should be used depends on the air void gradient produced by
the specific compactor, and the capabilities of the sawing equipment.
9.1.3 Perform mixture conditioning for the test specimens and companion maximum
specific gravity test in accordance with Section 7.2 of AASHTO R-30, Short-Term
Conditioning for Mixture Mechanical Property Testing.
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9.2 Gyratory Specimen Compaction
9.2.1 Compact the gyratory specimens in accordance with Section 9 of AASHTO T 312.
9.2.2 Compact the gyratory specimens to the target gyratory specimen height.
Note 7 Each laboratory should determine a target gyratory specimen height based
on the procedure for evaluating test specimen uniformity given in Appendix B, and an
evaluation of the ability of the sawing equipment to maintain the dimensional
tolerances given in Section 9.5.3.
9.3 Long-Term Conditioning (Optional)
9.3.1 If it is desired to simulate long-term aging, condition the gyratory specimen in
accordance with Sections 7.3.4 through 7.3.6 of AASHTO R-30.
9.3.2 To obtain accurate volumetric measurements on the long-term conditioned
specimens, also condition a companion sample of short-term conditioned loose mix
meeting the sample size requirements of AASHTO T 209 in accordance with Sections
7.3.4 through 7.3.6 of AASHTO R-30.
9.4 Gyratory Specimen Density and Air Voids (Optional)
9.4.1 Determine the maximum specific gravity of the mixture in accordance with AASHTO
T 209 (If long-term conditioning has been used, determine the maximum specific
gravity on the long-term conditioned loose mix sample). Record the maximum
specific gravity of the mixture.
9.4.2 For dense- and gap-graded mixtures, determine the bulk specific gravity of the
gyratory specimen in accordance with AASHTO T 166. Record the bulk specific
gravity of the gyratory specimen.
9.4.3 For open-graded mixtures, determine the bulk specific gravity of the gyratory
specimen in accordance with Section 6.2 of AASHTO T 269.
9.4.4 Compute the air void content of the gyratory specimen in accordance with AASHTO
T 269. Record the air void content of the gyratory specimen.
Note 8 Section 9.4 is optional because acceptance of the test specimen for
mechanical property testing is based on the air void content of the test specimen, not
the gyratory specimen. However, monitoring gyratory specimen density can identify
improperly prepared specimens early in the specimen fabrication process.
Information on gyratory specimen air voids and test specimens air voids will also
assist the laboratory in establishing potentially more precise methods than
Appendix A for preparing test specimens to a target air void content.
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9.5 Test Specimen Preparation
9.5.1 Drill a nominal 100 mm diameter core from the center of the gyratory specimen.
Both the gyratory specimen and the drill shall be adequately supported to ensure that
the resulting core is cylindrical with sides that are smooth, parallel, and meet the
tolerances on specimen diameter given in Section 9.5.3.
9.5.2 Saw the ends of the core to obtain a nominal 150 mm tall test specimen. Both the
core and the saw shall be adequately supported to ensure that the resulting test
specimen meets the tolerances given in Section 9.5.3 for height, end flatness and end
perpendicularity.
Note 9 With most equipment, it is better to perform the coring before the sawing.
However, these operations may be done in either order as long as the dimensional
tolerances in Section 9.5.3 are met.
9.5.3 Test specimens shall meet the dimensional tolerances given in Table 1.
Table 1. Test Specimen Dimensional Tolerances.
Item Specification Method
Average Diameter 100 mm to 104 mm 9.5.3.1
Standard Deviation of Diameter 0.5 mm 9.5.3.1
Height 147.5 mm to 152.5 mm 9.5.3 .2
End Flatness 0.5 mm 9.5.3.3
End Perpendicularity 1.0 mm 9.5.3.4
9.5.3.1 Using calipers, measure the diameter at the center and third points of the test
specimen along axes that are 90 ° apart. Record each of the six measurements to the
nearest 0.1 mm. Calculate the average and the standard deviation of the six
measurements. The standard deviation shall be less than 0.5 mm. Reject specimens
not meeting the average and standard deviation requirements listed in Table 1. The
average diameter, reported to the nearest 0.1 mm, shall be used in all material
property calculations.
9.5.3.2 Measure the height of the test specimen in accordance with Section 6.1.2 of ASTM
D 3549. Reject specimens with an average height outside the height tolerance listed
in Table 1. Record the average height.
9.5.3.3 Using a straightedge and feeler gauges, measure the flatness of each end. Place a
straight edge across the diameter at three locations approximately 120 ° apart and
measure the maximum departure of the specimen end from the straight edge using
tapered end feeler gauges. For each end record the maximum departure along the
three locations as the end flatness. Reject specimens with end flatness exceeding
0.5 mm.
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9.5.3.4 Using a combination square and feeler gauges, measure the perpendicularity of each
end. At two locations approximately 90 ° apart, place the blade of the combination
square in contact with the specimen along the axis of the cylinder, and the head in
contact with the highest point on the end of the cylinder. Measure the distance
between the head of the square and the lowest point on the end of the cylinder using
tapered end feeler gauges. For each end, record the maximum measurement from the
two locations as the end perpendicularity. Reject specimens with end
perpendicularity exceeding 1.0 mm.
9.6 Test Specimen Density and Air Voids
9.6.1 Determine the maximum specific gravity of the mixture in accordance with AASHTO
T 209 (If long-term conditioning has been used, determine the maximum specific
gravity on the long-term conditioned loose mix sample). Record the maximum
specific gravity of the mixture.
9.6.2 For dense- and gap-graded mixtures, determine the bulk specific gravity of the test
specimen in accordance with AASHTO T 166. Record the bulk specific gravity of
the test specimen.
Note 10 When wet coring and sawing methods are used, measure the immersed
mass followed by the surface dry mass followed by the dry mass to minimize drying
time and expedite the specimen fabrication process.
9.6.3 For open-graded mixtures, determine the bulk specific gravity of the test specimen in
accordance with Section 6.2 of AASHTO T 269. Record the bulk specific gravity of
the test specimen.
9.6.4 Compute the air void content of the test specimen in accordance with AASHTO
T 269. Record the air void content of the test specimen. Reject test specimens
exceeding the air void tolerances specified in the appropriate Standard Method of
Test.
9.7 Test Specimen Storage
9.7.1 Mark the test specimen with a unique identification number.
9.7.2 Store the test specimen on end on a flat shelf in a room with temperature controlled
between 15 and 27 °C until tested.
Note 11 Definitive research concerning the effects of test specimen aging on
various mechanical property tests has not been completed. Some users wrap
specimens in Saran wrap and minimize specimen storage time to two weeks.
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10. REPORTING
10.1 Unique test specimen identification number.
10.2 Mixture design number for link to pertinent mixture design data including design
compaction level and air void content, asphalt binder type and grade, binder content,
binder specific gravity, aggregate types and bulk specific gravitities, consensus
aggregate properties, and maximum specific gravity.
10.3 Type of aging used.
10.4 Maximum specific gravity for the aged condition.
10.5 Gyratory specimen target height (Optional).
10.6 Gyratory specimen bulk specific gravity (Optional).
10.7 Gyratory specimen air void content (Optional).
10.8 Test specimen average height.
10.9 Test specimen average diameter.
10.10 Test specimen bulk specific gravity.
10.11 Test specimen air void content.
10.12 Test specimen end flatness for each end.
10.13 Test specimen end parallelism for each end.
10.14 Remarks concerning deviations from this standard practice.
11. KEYWORDS
Performance test specimens; gyratory compaction
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APPENDIX A METHOD FOR ACHIEVING TARGET AIR VOID
CONTENT (NONMANDATORY INFORMATION)
A1. PURPOSE
A1.1 This Appendix presents a procedure for estimating the mass of mixture required to
produce test specimens at a target air void content. It was developed to reduce the
number of trial specimens needed obtain a target air void content for a specific
mixture.
A1.2 This procedure can be used with either plant produced or laboratory prepared
mixture.
A2. SUMMARY
A2.1 Trial test specimens are prepared as described in this standard practice from gyratory
specimens produced with a standard mass of 6,650 g and compacted to a standard
height of 170 mm.
A2.2 Based on the air void content of the trial specimens, the mass of mixture required to
produce test specimens at a target air void content is estimated using a regression
equation. Background information regarding the regression equation is presented in
Section A4.
A2.3 To use this method, it is critical that all gyratory specimens are prepared to a standard
height of 170 mm. The approach described in Section A4 can be used to develop a
similar equation for other gyratory specimen heights.
A3. PROCEDURE
A3.1 Prepare trial test specimen 1 and trial test specimen 2 following this standard practice
from gyratory specimens produced with a standard mass of 6,650 g and compacted to
a standard height of 170 mm.
A3.2 Determine the air void content of trial test specimen 1 and trial test specimen 2.
A3.3 Calculate the average air void content of the two specimens and designate this as Vas.
A3.4 Estimate the mass of mixture, Wt, required to produce test specimens with a target air
void content of Vat using Equation A1.
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Va t
Wt = 7175 - (525) (A1)
Va s
where:
Wt = estimated mass of mixture required to produce a gyratory specimen
for a test specimen with a target air void content of Vat, g
Vat = target air void content for the test specimen, vol %
Vas = test specimen air void content produced with a gyratory mass of
6,650 g, vol %
A3.5 Prepare trial test specimen 3 following this standard practice from a gyratory
specimen produced with the target mass estimated in Section A3.4 and compacted to
the standard height of 170 mm.
A3.6 Determine the air void content of trial test specimen 3.
A3.7 If the air void content of trial test specimen 3 is within ± 0.5 percent of the target, use
the mass determined in A3.4 as the target mass for test specimen production.
A3.8 If the air void content of trial test specimen 3 is not within ± 0.5 percent of the target,
prepare trial specimen 4 using 50g less than calculated in A3.4 and trial test specimen
5 using 50g more than calculated in A3.4.
A3.9 Determine the air void content of trial test specimen 4 and trial test specimen 5.
A3.10 Plot the air void content of trial test specimens 3, 4, and 5 (y) against the mass of
mixture used to prepare the gyratory specimen (x), and draw the best-fit line through
the three data points.
A3.11 From the best-fit line, determine the mass of mixture needed to produce a test
specimen with the target air void content.
A3.12 Use the mass determined in A3.11 as the target mass for test specimen production.
A4. BACKGROUND
A4.1 The method described in this Appendix was developed by the Arizona State
University during NCHRP Project 9-19. It is based on analysis of 38 different
mixtures, where test specimens were prepared to varying target air void contents
representative of in-situ conditions.
A4.2 For a given mixture, when gyratory specimens are prepared to a specific height, the
relationship between the mixture mass used to prepare the gyratory specimen and the
air void content of the test specimens was found to be linear.
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Va = I + S (W ) (A2)
where:
Va = test specimen air void content, vol %
W = mass of mixture used to produce the gyratory specimen
I = intercept of the regression line
S = slope of the regression line
A4.3 When a wide range of mixtures is considered, the intercepts and slopes for individual
mixtures were also found to be linearly related.
I = -C ( S ) (A3)
where:
I = intercept of individual mixture regression lines
S = slope of individual mixture regression lines
C = constant
A4.4 In the NCHRP Project 9-19 research, the constant, C, was found to be 7,175 for
gyratory specimens prepared to a standard height of 170 mm. Substituting this
constant into Equation A3, then substituting Equation A3 into Equation A2 and
simplifying, yields an equation relating the air void content of the test specimen to the
mass of mixture used to prepare the gyratory specimen to the standard height of 170
mm.
Va = S (W - 7175) (A4)
A4.5 If gyratory specimens are compacted using a standard mass, Ws, and the air void
contents for the resulting test specimens are determined to be Vas, then Equation A4
can be solved for the slope.
Va s
S= (A5)
W s - 7175
where:
Vas = test specimen air void content produced with a gyratory mass of Ws,
vol %
Ws = mass of mixture used to produce the gyratory specimen, g
S = slope of the regression line
A4.6 Using the slope from Equation A5, the target gyratory specimen mass, Wt, required to
produce a test specimen with a specific air void content, Vat, can be estimated by
substituting Equation A5 into Equation A4 and simplifying.
Va t
Wt = 7175 + (W s - 7175) (A6)
Va s
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where:
Wt = estimated mass of mixture required to produce a gyratory specimen
for a test specimen with a target air void content of Vat, g
Vat = target air void content for the test specimen.
Vas = test specimen air void content produced with a gyratory mass of Ws,
vol %
Ws = mass of mixture used to produce the gyratory specimen
A4.7 For a standard mixture mass of 6,650 g, which was the average mass used in the
NCHRP 9-19 study, Equation A6 reduces to.
Va t
Wt = 7175 - (525) (A6)
Va s
where:
Wt = estimated mass of mixture required to produce a gyratory specimen
for a test specimen with a target air void content of Vat, g
Vat = target air void content for the test specimen.
Vas = test specimen air void content produced with a gyratory mass of Ws,
vol %
Ws = mass of mixture used to produce the gyratory specimen
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APPENDIX B TEST SPECIMEN UNIFORMITY
(NONMANDATORY INFORMATION)
B1. PURPOSE
B1.1 This Appendix presents a procedure for assessing the uniformity of the air void
content in test specimens produced using this standard practice.
B1.2 The approach tests the significance of the difference in mean bulk specific gravity
between the top and bottom third of the specimen relative the middle third.
B1.3 The procedure can be used to determine the height for preparing gyratory specimens
with a specific compactor to minimize within sample variations in air voids.
B2. SUMMARY
B2.1 Three test specimens are prepared as described in this standard practice from gyratory
specimens produced with the same mixture mass and compacted to the same height.
B2.2 The test specimens are cut into three slices of equal thickness and the bulk specific
gravity or each slice is determined.
B2.3 A statistical hypothesis test is conducted to determine the significance of differences
in the mean bulk specific gravity of the top and bottom slices relative to the middle.
B3. PROCEDURE
B3.1 Prepare three test specimens following this standard practice to a target air void
content of 5.5 percent. All three specimens shall have air void contents within the
range of 5.0 to 6.0 percent.
B3.2 Label the top, middle, and bottom third of each specimen, then saw the specimens at
the third points.
B3.3 Determine the bulk specific gravity of each of the nine test section slices in
accordance with AASHTO T 166 for dense- and gap-graded mixtures or AASHTO
T 269 for open-graded mixtures.
B3.4 Assemble a summary table of the bulk specific gravity data where each column
contains data for a specific slice, and each row contains the data from a specific core.
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B3.5 For each column, compute the mean and variance of the bulk specific gravity
measurements using Equations B1 and B2.
3
y
i =1
i
y= (B1)
3
3
(y
i =1
i - y) 2
s2 = (B2)
2
where:
y = slice mean
s2 = slice variance
yi = measured bulk specific gravities
B3.6 Statistical Comparison of Means- Compare the mean bulk specific gravity of the top
and bottom slices to the middle slice using the hypothesis tests described below. In
the descriptions below, subscripts "t", "m", and "b" refer to the top, middle, and
bottom slices, respectively.
B3.6.1 Check the top relative to the middle.
Null Hypothesis:
The mean bulk specific gravity of the top slice equals the mean bulk specific gravity
of the middle slice, t = m
2 2
Alternative Hypothesis:
The mean bulk specific gravity of the top slice is not equal the mean bulk specific
gravity of the middle slice, t m
2 2
Test Statistic:
(yt - y m )
t= (B3)
0.8165( s )
where:
st + s m
2 2
s= (B4)
2
y t = computed mean for the top slices
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y m = computed mean for the middle slices
st2 = computed variance for the top slices
sm2 = computed variance for the middle slices
Region of Rejection:
For the sample sizes specified, the absolute value of the test statistic must be less
than 2.78 to conclude that bulk specific gravity of the top and middle slices are
equal.
B3.6.2 Check the bottom relative to the middle.
Null Hypothesis:
The mean bulk specific gravity of the bottom slice equals the mean bulk specific
gravity of the middle slice, b = m
2 2
Alternative Hypothesis:
The mean bulk specific gravity of the bottom slice is not equal the mean bulk specific
gravity of the middle slice, b m
2 2
Test Statistic:
(y b - y m )
t= (B5)
0.8165( s )
where:
sb + s m
2 2
s= (B4)
2
y b = computed mean for the bottom slices
y m = computed mean for the middle slices
sb2 = computed variance for the bottom slices
sm2 = computed variance for the middle slices
Region of Rejection:
For the sample sizes specified, the absolute value of the test statistic must be less
than 2.78 to conclude that bulk specific gravity of the bottom and middle slices
are equal.
B4. ANALYSIS
B4.1 Significant differences in the bulk specific gravity of the top and bottom slices
relative to the middle indicate a systematic variation in density within the specimen.
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B4.2 Specimens with differences for the top and/or bottom slices relative to the middle
slices on the order of 0.025 have performed satisfactorily in the dynamic modulus,
flow number, flow time, and continuum damage fatigue tests.
B4.3 Changing the height of the gyratory specimen can improve the uniformity of the
density in the test specimen.
