A SuperpaveTM Hot Mix Asphalt Mix Design Completed
in Conjunction with Testing Lab Set-up and Procedures
By
Stephen J. Palmer
April 2001
A Research Paper Submitted in Partial Fulfillment
of the Requirements for the Master of Science Degree
Department of Civil Engineering
Southern Illinois University Edwardsville
2
Abstract
The major focus of this Masters project was to develop a familiarity with the Hot Mix Asphalt (HMA)
mix design process using both Superior Performing Asphalt Pavement (SuperpaveTM) methods and
Illinois Department of Transportation (IDOT) specifications. In order to facilitate understanding the
mix design process, a bituminous testing lab was needed to verify the target value specifications for the
mix design. As a further part of this project, a bituminous lab in the new Engineering Building was
established. In conjunction with the move to the new building, the Civil Engineering Department had
purchased much of the necessary testing equipment to facilitate completing HMA mix designs. The
goal was to utilize the HMA mix design as a means to set-up the lab and the related equipment.
Through the mix design process the asphalt and aggregate testing equipment would be set-up,
calibrated, and made operational by the end of Fall 2000 semester. Furthermore, a procedures manual
for both instructors and students would be authored to aid in the development of a pavement design lab
course.
Procedures and methods published from the Asphalt Institute, the American Association of State
Transportation Officials (AASHTO), ASTM, and IDOT were followed for the mix design and testing.
For new equipment operation, manufacturer’s provided documentation was utilized.
Due to a lack of equipment, functional problems with existing and new equipment, and time
constraints, much of the data obtained from the HMA mix design did not meet target values. However,
the aggregate testing values for soundness and sand equivalent did meet prescribed criteria.
In summary, the project goal of establishing a bituminous testing lab was achieved. Through the mix
design process, all the equipment was calibrated and used. However, the results of the HMA
experiment were inconclusive due in part to the reasons stated above.
3
TABLE OF CONTENTS
ABSTRACT………………………………………………………………………………………. 2
ACKNOWLEDGEMENTS……………………………………………………………… ………4
DISCLAIMERS……………………………………………………………………………………4
LIST OF TABLES…………………………………………………………………………………5
CHAPTER
I. INTRODUCTION ………………………………………………………………………6
II. PROBLEM STATEMENT…………………………………………………………….9
III. METHODS…………………………………………………………………………….11
IV. RESULTS…………………………………………………………………………….. 19
V. SUMMARY……………………………………………………………………………..21
VI. REFERENCES……………………………………………………………………….. 23
VII. APPENDICES………………………………………………………………………..25
A. EXPERIMENTAL DATA AND SAMPLE CALCULATIONS……………. 25
B. RECOMMENDATIONS TO THE CIVIL ENGINEERING
DEPARTMENT……………………………………………………………….. 28
C. RAINHART GYRATORY COMPACTOR PROBLEM LOG…………….. 29
D. STUDENT LAB MANUAL……………………………………………………31
E. INSTRUCTOR LAB MANUAL ………………………………………………36
F. APPARATUS……………………………………………………………………42
4
Acknowledgements
I would like to thank several individuals for their help and contribution in making this project a
success. First I would like to acknowledge the contribution from my advisor Dr. Chiang Lin, Ph.D.,
who was the calm in the storm. Furthermore, this project could not have been completed in the time
frame established without the dedication of Mr. Brent Vaughn, CE Department Lab Specialist, who’s
instrumentation experience and attention to detail proved invaluable. Finally I would like to thank Mr.
Roger Hayden of Reese Construction, Cahokia, IL. Through Roger, Reese Construction donated all the
asphalt and aggregate materials necessary for the HMA mix design and provided unlimited access to
their own lab, which proved extremely beneficially. Roger and Ken also provided considerable insight
into the nuances of IDOT’s specifications and mix design criteria.
Disclaimers
For this project mineral aggregates were sampled from stockpiles located at Reese Construction’s yard.
Data on average gradation and specific gravity of each individual aggregate was utilized since these
values were previously tested and found to be in conformance to IDOT’s specifications. Furthermore,
the asphalt binder used was provided by Reese Construction and certified by the manufacturer, so no
other attempt was made to verify that it met SuperpaveTM criteria as testing for these properties was
beyond the scope of this project.
5
List of Tables
Table 1
IL 9.5mm Mixture Aggregate Gradation by Percent Passing
Table 2
Aggregate Testing Employed
Table 3
Aggregate Stockpile Gradations (Reese Construction)
Table 4
Trial Aggregate Blend
Table 5
Trial Batch Weights
Table 6
CA16 Batch Weights
Table 7
FA21 Batch Weights
Table 8
FA01 Batch Weights
Table 9
MF Batch Weight
Table 10
Asphalt Binder Batch Weight
Table 11
LA Abrasion Test Results
Table 12
Sand Equivalent Test Results
Table 13
Sulfate Soundness Test Results
Table 14
Asphalt Binder Content Ignition Oven Method Results
Table 15
Specific Gravity Results
Table 16
Volumetric Mix Results
6
Introduction
Superior Performing Asphalt Pavements (SuperpaveTM) were developed through the Strategic
Highway Research Program (SHRP) in an attempt to improve overall highway pavement performance.
The primary areas of improvement sought were in pavement rutting, low temperature cracking, and
fatigue cracking. This was achieved by orienting the pavement design methodology towards the
environmental conditions that the pavement could expect to experience during the design life, together
with the traditionally used loading expectations (13).
SuperpaveTM is a performance based mix design and analysis process that evaluates both constituent
materials and final mixture performance. The liquid asphalt binder is evaluated for performance based
on the criteria of temperature, time of loading, and aging factors, while the constituent mineral
aggregates are evaluated based on surface characteristics, particle shape, and gradation (13). Finally,
once combined into an HMA mixture, this mixture is evaluated for performance under various loading
and environmental field conditions.
The asphalt binders are selected for a particular mix design specification based primarily on the
climate that the binder will experience. This was accomplished by reviewing climate history, high and
low air temperatures, and relating the air temperature history to corresponding pavement temperatures.
A statistical model was then employed to determine the probability of occurrence of these high and
low temperatures. Based on the climatic variation, the asphalt binders are tested and labeled according
to performance. An asphalt binder that is expected to perform adequately in a climate with an average
7-day maximum temperature of 64oC and a minimum pavement design temperature of –22oC would be
labeled PG 64-22(13). The PG stands for performance grade and the numbers correspond to the high
7
and low temperature variation. For practical reasons, many states implementing Superpave
TM
, employ
a system of designating a particular performance grade asphalt binder to the various districts or
geographic areas, thus saving the designer time.
Mineral aggregate performance-based gradation selection is accomplished through the use of what is
termed in SuperpaveTM the 0.45 power chart (13). Although such characteristics as material toughness,
soundness, angularity, elongation, blend clay content, and deleterious percentage are used in selecting
aggregates for use in the mix design, the aggregate blend gradation is the most mix specific
characteristic. The 0.45 power chart is simply a graph of the sieve sizes in millimeters raised to the
0.45 power, placed along the x-axis, and the percent passing of the aggregate blend, placed along the
y-axis. The chosen trial blend gradation is plotted on the chart and compared to a maximum density
line and certain restricted zones and control points, included to promote friction and point-to-point
contact of the aggregate, thus reducing rutting. As previously stated, the researchers involved in
developing SuperpaveTM attempted to reduce the rutting of in-place pavements. This was accomplished
by restricting an area of the gradation curve in the fine aggregate region so that point-to-point contact
of the particles was encouraged. This area is known as the restricted zone and the blend cannot pass
through this region. The maximum gradation line represents the densest possible arrangement of the
aggregate. It is established by running a line from the origin to a point of 100 percent passing at a sieve
size one size larger than the nominal maximum sized for the aggregate blend (13). An example of an
Illinois 9.5 mm (surface mix) follows, as shown in Figure 1, to demonstrate how the 0.45 power chart
works.
8
Figure 1. 0.45 Power Chart for an IL 9.5 mm Surface Mixture
The final parameter used in a SuperpaveTM mix design is a traffic loading termed designated as
Equivalent Single Axle Loading (ESAL), which relates the damage to a pavement by a single
equivalent 18-kip axle load. This term is related empirically to the traffic volume that the in-place
pavement would be expected to experience at the end of the design life (13). The completed mix is
evaluated in the lab by compaction in a gyratory compactor, specifically designed for the SuperpaveTM
method. Using the calculated ESAL’s, the number of gyrations the mix is subjected to is determined
and this number is designated as Ndesign (13). Thus, the loading component the pavement will
experience is simulated by compacting the mix specimen at a pre-set pressure of 600 KPa and a
determined number of gyrations.
9
Finally, the mix as a whole is volumetrically evaluated by calculating the Voids in Mineral Aggregate
(VMA) and the Voids Filled with Asphalt (VFA) at a target value of 4% Air Voids (Va). Many states
set target values for VMA and VFA at the 4% air voids point. If the values for VMA and VFA are not
met, the mix is rejected and cannot enter production.
The Illinois Department of Transportation (IDOT) has implemented most of the SuperpaveTM criteria
with some modifications. Since pre-SuperpaveTM IDOT specifications already addressed the aggregate
properties of toughness, soundness, and deleterious material, the SuperpaveTM guidelines were not
specifically incorporated into the IDOT specifications. Also, IDOT uses the control points in the 0.45
power chart as a guide only. Meeting VMA and VFA criteria is considered a more important factor in
the overall pavement performance.
Problem Statement
The primary goal of this endeavor was to gain an understanding of the SuperpaveTM mix design
methodology. In order to achieve this, the task was undertaken to complete an actual HMA mix design
using a combination of IDOT and general SuperpaveTM guidelines. A hypothetical highway design
situation was chosen so that as many of the SuperpaveTM parameters as possible could be applied, and
also to utilize all of the testing equipment available in the SIUE CE Department’s lab. It was decided
not to evaluate mix characteristics and material properties if appropriate equipment was not available.
The control road design project and mix design methodology are specified as follows:
Mix design method and specifications: IDOT and SuperpaveTM
Highway Design Criteria
Functional classification: Rural collector
Highway type: county road
Average Daily Traffic (ADT) = 1500
Design ESAL’s = 1,000,000
10
Geographic area: southwest central Illinois, IDOT Collinsville District 8
Type of mixture: Surface mix
Materials: virgin materials
Based on the previously stipulated design criteria the following mixture design was determined based
on IDOT’s specifications.
Mix Designation
IL 9.5 mm (9.5 mm maximum size of aggregate particle)
Mixture Type C (IDOT friction requirement, ADT<2000)
SuperpaveTM design gyrations: Ndesign = 50 (ESAL’s 0.3 to 3 million)
Asphalt Binder: PG 64-22 (Collinsville District 8)
Mineral Aggregate Selection
Course Aggregate:
CA 16- crushed Limestone
Fine Aggregate:
FA 01 – river sand
FA 21 – slag sand
Mineral Filler:
MF – Limestone dust
Volumetric Requirements
VMA = 15% minimum
VFA = 65-78%
Va = 4% standard target
Table 1. IL 9.5mm Mixture Aggregate Gradation Percent Passing
Sieve
12.5
9.5
4.75
2.36
1.18
300
150
µm
µm
Size
mm
mm
mm
mm
mm
(#50)
(#100)
(1/2”)
(3/8”)
(#4)
(#8)
(#16)
Minimum -------90
24
16
10
4
3
Maximum
100
100
65
48
32
15
10
75
µm
(#200)
Table 2. Aggregate Testing Employed
Properties
Test
Designation
IDOT Requirement
Toughness
LA Abrasion
AASHTO T96-94
45% maximum loss
Sand Equivalent
Sand Equivalent
AASHTO T176-86
40% minimum
Soundness
Sulfate Soundness AASHTO T104-87 20% maximum loss
4
16
11
The constituent aggregates will be tested following the procedures detailed above. The asphalt binder
used in the mix design was certified by the manufacturer. Actual testing of asphalt binder is beyond the
scope of the project due to a lack of proper testing equipment. The actual mixture will be evaluated for
VMA, VFA, and Percent Air Voids using the SuperpaveTM gyratory compactor, bulk specific gravity
apparatus, and maximum theoretical specific gravity pycnometers. Final asphalt binder content will be
verified using the NCAT Asphalt Ignition Oven.
Methods
The mineral aggregate testing followed the AASHTO and ASTM specifications referenced. Since the
new lab was equipped with a Los Angeles Abrasion machine, Sulfate Soundness apparatus, and Sand
Equivalent testing equipment, only the toughness, soundness, and sand equivalent tests on the
aggregates were performed. Due to the specific nature of the AASHTO and ASTM testing procedures,
the particular methods used for these tests will not be repeated.
The asphalt binder was selected using IDOT’s PG Binder Grade Selection-Full Depth Asphalt Table
for Districts 7-9 (29). Again no attempt was made to verify the chemical or physical properties of the
liquid asphalt binder material as this was beyond the scope of this project.
The coarse aggregate, CA 16 (Limestone), was selected because it met the friction requirements as
shown in IDOT’s Table 3 Friction Aggregates in Surface Mixtures (29). All mineral aggregates were
donated by Reese Construction, Cahokia, IL, and their stockpile average gradation results and specific
12
gravities were used to determine the mix blend, which is required to meet IDOT’s general gradation
chart and the parameters of the 0.45 power chart. No attempt was made to verify the stockpile averages
as these values are verified by IDOT for use in state highway projects.
The basic methodology for the SuperpaveTM system involves blending the mineral aggregate in proper
proportion so that gradation requirements are met. The standard IDOT SuperpaveTM batch weight
target value is 14,000g. Therefore, once the proportion of each aggregate is selected, it is then plotted
on the 0.45 power chart to determine whether that particular blend will meet the gradation
requirements. Then based on the designer’s experience, an asphalt binder content is selected. Finally,
the batch weights of each material are calculated so that a sample mixture can be made. Then the
aggregates and asphalt binder are batched with the correct weights and preheated to 295oF or a
particular specification. Once heated, the aggregates and asphalt binder are combined in a blending
apparatus, which is operated until all the aggregate is coated with asphalt binder. Following the
blending operation, the mix is placed in the oven to condition. This conditioning operation is done to
simulate what happens to the mixture during transport to the job site. After the conditioning process is
complete, part of the batch is utilized in conjunction with the gyratory compactor and the remaining
mix is used to determine the theoretical maximum specific gravity.
The mix selected for use in the gyratory machine is placed in a heated mold and then subjected to the
specified gyratory compaction effort. The number of gyrations was previously determined as Ndesign =
50 based on the design ESAL’s = 1,000,000. In the compactor, the mix is compacted into a disk shape.
The Bulk Specific Gravity, Gmb, of the disk or puck, as it is sometimes referred to, is then determined.
The remaining mixture is used in loose form to find the Maximum Theoretical Specific Gravity, Gmm.
Using these two values along with the Aggregate Percentage By Weight, Ps, and the Combined Bulk
Specific Gravity of the Aggregate Blend, Gsb, the volumetric properties of the mix, namely the Voids
13
in Mineral Aggregate (VMA), Voids Filled with Asphalt (VFA), and Percent Air Voids (Va) can be
calculated. Refer to Appendix A for sample calculations.
If the standard 4% Air Voids value is met along with the VMA and VFA criteria, the designer is done
and the mix can go into production. This, however, almost never happens so exactly on the first
attempt. Generally several asphalt binder contents are selected for a particular aggregate blend. All the
trials are then batched and evaluated for their volumetric characteristics. Then the asphalt binder
content is plotted against Percent Air Voids and used to determine the optimum asphalt binder content
for that particular aggregate blend at the 4% air voids mark. The following plot illustrates this
situation.
Figure 2. Optimum Asphalt Binder Content
Due to equipment problems and time constraints, only one asphalt binder content for the aggregate trial
blend was selected. IDOT suggestions and testing criteria in batching and conditioning the mixture
were closely followed.
14
Mix Design Steps
The following steps illustrate the method used in formulating the mix design values. It should be noted
that the asphalt binder content selected was based on the author’s previous experience as a highway
design engineer. Otherwise, there is no particular method for determining the optimum binder content
except to select various percentages and plot them against percent air voids results as previously
illustrated.
(1) The first step involves determining the gradations of the individual mineral aggregates. The
gradations listed in Table 3 are average percent passing values from Reese Construction’s stockpiles.
Table 3. Aggregate Stockpile Gradations (Reese Construction)
Percent Passing
Aggregate
½” 3/8”
Specification
CA 16
100 98
#4
#8
#16 #30 #50 #100 #200
30
4
3
3
3
3
2.4
FA 01
100
100
99
92
73
30
9
1
0.1
FA 21
100
100
100
77
53
34
21
12
7.2
MF
100
100
100 100 100 100 100
98
93
15
(2) Next, using the gradations in Table 3 and the following selected aggregate percentages, the trial
aggregate blend is determined. An example for calculating the 3/8” sieve size follows:
CA 16
FA 01
FA 21
MF
98*(0.575) =
100*(0.19) =
100*(0.22) =
100*(0.015) =
TOTAL
56.4
19.0
22.0
1.5
Trial Blend 1 (3/8” Sieve)
98.9
Table 4. Trial Aggregate Blend
Sieve Trial
Size Blend 1
IDOT
CA 16 FA 01 FA 21 MF
Specs
57.5% 19% 22% 1.5%
Min Max
½”
100
--
100
57.5
19.0
22.0
1.5
3/8”
98.9
90
100
56.4
19.0
22.0
1.5
#4
59.6
24
65
17.3
18.8
22.0
1.5
#8
38.2
16
48
2.3
17.5
16.9
1.5
#16
28.8
10
32
1.7
13.9
11.7
1.5
#30
16.4
--
--
1.7
5.7
7.5
1.5
#50
9.5
4
15
1.7
1.7
4.6
1.5
#100
6.0
3
10
1.7
0.2
2.6
1.5
#200
4.4
4
16
1.4
0.0
1.6
1.4
16
(3) Once the trial blend is determined, it needs to be plotted on the 0.45 power chart to ensure it
doesn’t enter in the restricted zone. As can be viewed from the plot below, the aggregate trial blend
does meet the SuperpaveTM gradation criteria.
Figure 3. Trial Aggregate Blend Chart
17
(4) The next step is to determine the aggregate batch weights. This is necessary because the percent
passing values do not indicate the amount of mineral aggregate needed in the batch. The sample batch
weight for the mix design is established at the standard target 14,000g for the mineral aggregate
portion. The asphalt binder content will be added to the aggregate amounts to form the total batch
weight to be used.
Table 5. Trial Batch Weights
Aggregate
Calculation
Batch Weight (g)
CA 16
14,000*57.5%
8050
FA 01
14,000*19.0%
2660
FA 21
14,000*22.0%
3080
MF
14,000*1.5%
210
Aggregate Batch
Total
14,000 g
(5) Next, the individual sieve sizes for each aggregate need to be calculated from the total batch so that
after sieving and drying, the individual weights for material retained on the sieves can be added for
batching. An extrapolated example of the CA 16 aggregate is shown. The other aggregate batch
weights are simply presented in their final form.
18
CA 16
Table 6. CA 16 Batch Weights
Sieve Size Sieve Size Percent
Passing
Retained Retained
½”
3/8”
2
Weight (g)
0.02*8050 = 161.0
Accumulated
Weight (g)
161.0
3/8”
#4
68
0.68*8050 = 5474.0
5635.0
#4
#8
26
0.26*8050 = 2093.0
7728.0
#8
#30
1
0.01*8050 = 80.5
7808.5
#30
PAN
3
0.03*8050 = 241.5
8050.0
FA 21
Table 7. FA 21 Batch Weights
Passing Retained Percent Weight (g) Accumulated
Sieve
Sieve
Retained
Weight (g)
-#8
23
708.4
8758.4
#8
#30
43
1324.4
10082.8
#30
PAN
34
1047.2
11130.0
FA 01
Table 8. FA 01 Batch Weights
Passing Retained Percent Weight (g) Accumulated
Sieve
Sieve
Retained
Weight (g)
-#8
8
212.8
11342.8
#8
#30
62
1649.2
12992.0
#30
PAN
30
798.0
13790.0
MF
Table 9. MF Batch Weights
Passing Retained Percent Weight Accumulated
Sieve
Sieve
Retained
(g)
Weight (g)
#30
PAN
100
210.0
14000.0
19
(6) Notice that the trial batch weight summed to 14,000 g. Finally, an asphalt binder percentage of 5%
was chosen as a beginning point. The final computation for batch weight is shown.
Table 10. Asphalt Binder Batch Weight
AC Binder Percentage
Batch Weight (g)
Accumulated
Weight (g)
Asphalt Binder % = 5% 0.05*14,000.0 = 736.8 g
14736.8 g
Results
The results of the mineral aggregate testing follow:
Table 11. LA Abrasion Test Results
LA
Abrasion
Test 1
Result
51%
IDOT
Spec
45% max loss
Test 2
27%
45% max loss
Remarks
Does not meet spec
5005g retained on the #4 sieve
Meets spec
4003.8g retained on the #4 sieve
1001.6g retained on the 3/8”
Table 12. Sand Equivalent Test Results
Sand Equivalent Result
(Clay Content)
Test 1
100%
IDOT
Spec
40% min
Remarks
Meets spec
20
Table 13. Sulfate Soundness Test Results
Aggregate
Designation
Sieve
Size
Percent (%)
Retained
Weight of Test
Fractions (g)
Percent Passing
After Test
Weighted Percent
Loss
FA 01
#50
21
111.66
1.3
0.3
FA 01
#30
43
118.51
1.9
0.8
FA 01
#16
19
119.70
3.4
0.7
FA 01
#8
7
116.15
7.2
0.5
FA 01
#4
1
110.82
7.2*
0.1
Total
2
13.8
9.4
Total
9
CA 16
#4
68
118.90
* % Loss of next smaller sieve as per AASHTO T104-97
The results of the HMA testing follow:
Table 14. Asphalt Binder Content Ignition Oven Method Results
Test 1
Result
Batched %
Remarks
5.0%
5.0%
Matched indicated value
Table 15. Specific Gravity Results
Maximum Theoretical Specific Gravity of Loose HMA, Gmm 2.425
Bulk Specific Gravity of Compacted HMA, Gmb
2.277
Bulk Specific Gravity of Combined Aggregate, Gsb
2.630
IDOT
Spec
20%
max
20%
max
21
Table 16. Volumetric Mix Results
Result
Voids in Mineral Aggregate, VMA
18%
IDOT
Spec
15%
Remarks
Voids Filled with Asphalt, VFA
66%
65-75%
Meets spec
Air Voids, Va
6.1%
4.0%
Higher than
target value
Meets spec
Summary
The results of the aggregate and HMA tests show some inconsistency compared to the IDOT
specification target values. This was attributed to either lack of necessary equipment or equipment
functioning improperly. The results of the Sand Equivalent Test and the Sulfate Soundness Test were
the only accurate results determined. This is due to the fact that for both tests, appropriate testing
equipment was available for use. For all the other tests, there was a missing link in the process, as
either a lack of equipment existed or the equipment that was available functioned improperly.
However, this is not considered a problem. In fact, since the primary goal of the project was to
complete a HMA mix design as a means of establishing the Department’s testing lab, it only follows
that there would be some roadblocks in the way. These roadblocks caused problems with the results,
but more importantly, justified the need to make improvements to the lab. The inconsistent results
pointed out in a rather glaring way the need for improvement to the asphalt lab facility. The
improvements are detailed in recommendation form in Appendix B.
From the mix design process, it was discovered that the lab needed a more accurate pycnometer and
vacuum pump so that a more precise value for Maximum Theoretical Specific Gravity could be made.
Furthermore, the Rainhart Superpave Gyratory Compactor never did work properly, although it was
22
purchased new by the Department. This piece of equipment is of the utmost importance in achieving
accurate results in a SuperpaveTM mix design process. At the time of this report, another new gyratory
compactor was shipped and received by the Department. Mr. Brent Vaughn verified that it was indeed
working properly by the end of the Fall 2000 Semester.
Since the lab was functioning at the end of Fall 2000 Semester, the project was considered to be
successful. The original goal of developing an operational bituminous testing lab was met. There are
some needed improvements to be made, but with a small investment the Department can expect to
provide a quality environment in the future for the student to learn about HMA mix design and testing.
23
References
1) AASHTO. (1997). “Standard Specification for Plastic Fines in Graded Aggregates and Soils by Use
of the Sand Equivalent Test.” T176-86, Washington D.C.
2) AASHTO. (1997). “Standard Specification for Soundness of Aggregate by Use of Sodium Sulfate
or Magnesium Sulfate.” T104-97, Washington D.C.
3) AASHTO. (1994). “Standard Specification for Resistance to Degradation of Small-size Course
Aggregate by Abrasion and Impact in the Los Angeles Machine.” T96-94, Washington D.C.
4) AASHTO. (1997). “Standard Specification for Sieve Analysis of Fine and Course Aggregate.”
T27-97, Washington D.C.
5) AASHTO. (1991). “Standard Specification for Clay Lumps and Friable Particles in Aggregate.”
T112-91, Washington D.C.
6) AASHTO. (1995). “Standard Specification for Sieve Analysis of Mineral Filler for Road and Paving
Materials.” T37-95, Washington D.C.
7) AASHTO. (1989). “Standard Specification for Resistance of Compacted Bituminous Mixture to
Moisture Induced Damage.” T283-89, Washington D.C.
8) AASHTO. (1993). “Standard Specification for Bulk Specific Gravity of Compacted Bituminous
Mixtures Using Saturated Surface-Dry Specimens.” T166-93, Washington D.C.
9) AASHTO. (1995). “Standard Specification for Specific Gravity and Absorption of Fine Aggregate.”
T84-95, Washington D.C.
10) AASHTO. (1991). “Standard Specification for Specific Gravity and Absorption of Course
Aggregate.” T85-91, Washington D.C.
11) AASHTO. (1999). “Standard Method of Test for Determining the Asphalt Binder Content of Hot
Mix Asphalt (HMA) by the Ignition Method.” T308-99, Washington D.C.
12) AASHTO. (1995). “Standard Specification for Specific Gravity of Soils.” T100-95, Washington
D.C.
13) Asphalt Institute. (1996). “Superpave Mix Design: Superpave Series No. 2 (SP-2).” U.S.A.
14) Asphalt Institute. (1996). “Performance Graded Asphalt Binder Specification and Testing:
Superpave Series No. 1 (SP-1).” U.S.A.
15) Asphalt Institute. “Construction of Hot Mix Asphalt Pavements, Manual Series No. 22, 2nd
Edition.” Lexington, Kentucky.
16) ASTM. (1998). “Standard Test Method for Uncompacted Void Content of Fine Aggregate (as
Influenced by Particle Shape, Surface Texture, and Grading).” C1252, West Conshohocken, Pa.
24
17) ASTM. (1995). “Standard Test Method for Flat Particles, Elongated Particles, or Flat and
Elongated Particles in Course Aggregate.” D4791, West Conshohocken, Pa.
18) ASTM. (1995). ”Standard Test Method for Sand Equivalent Value of Soils and Fine Aggregate.”
D2419, West Conshohocken, Pa.
19) ASTM. (1999a).” Standard Test Method for Soundness of Aggregates by Use of Sodium Sulfate or
Magnesium Sulfate.” C88, West Conshohocken, Pa.
20) ASTM. (1996). ”Standard Test Method for Resistance to Degradation of Small-0size Course
Aggregate by Abrasion and Impact in the Los Angeles Machine.” C131, West Conshohocken, Pa.
21) ASTM. (1996a).” Standard Test Method for Sieve Analysis for Fine and Course Aggregates.”
C136, West Conshohocken, Pa.
22) ASTM. (1994). ”Standard Test Method for Sieve Analysis of Mineral Filler for Road and Paving
Materials.” D546, West Conshohocken, Pa.
23) ASTM. (1993). ”Standard Test Method for Specific Gravity and Absorption of Course Aggregate.”
C127, West Conshohocken, Pa.
24) ASTM. (1997). ”Standard Test Method for Specific Gravity and Absorption of Fine Aggregate.”
C128, West Conshohocken, Pa.
25) Foo, Kee Y., and Kandhal, Privthi S. (1998). “Adapting Superpave Technology to Design of Hot
Recycled Mixes.” Journal of Testing and Evaluation 26.3, 203-212.
26) Illinois Department of Transportation. (1997). “Standard Specifications for Road and Bridge
Construction.” State of Illinois.
27) Illinois Department of Transportation. (2000). “Illinois Modified Test Procedure: Standard
Specification for Superpave Volumetric Mix Design.” State of Illinois.
28) Illinois Department of Transportation. (2000). “Illinois Modified Test Procedure: Standard Practice
for Superpave Volumetric Design for Hot-Mix Asphalt (HMA).” State of Illinois.
29) Illinois Department of Transportation. (1996). “Illinois Superpave Mix Design and Bituminous
Level III Update Course.” State of Illinois.
30) Kandhal, Prithvi S., Parker Jr., Frazier, and Mallick, Rajib B. (1997). “Aggregate Tests for Hot
Mix Asphalt: State of the Practice.” NCAT Report No. 97-6, Auburn University, Al.
31) NAPA Research and Education Foundation. (1996). “Hot Mix Asphalt Materials, Mixture Design
and Construction.” 2nd Edition, Lanham, Maryland.
32) National Center for Asphalt Technology. (1998). “Professor Training Course in Asphalt
Technology.”
33) SHRP. (1994). “Level One Mix Design: Materials Selection, Compaction, and Conditioning.”
National Research Council, Washington D.C.
25
Appendix A
Experimental Data and Sample Calculations
A. Sand Equivalent Test (AASHTO T176-86)
Temperature = 67oF
Original Fine Aggregate Amounts
FA 01 = 804.9 g
FA 21 = 695.1 g
Total = 1500.0 g
Sand Reading = 4.0
Clay Reading = 4.0
Sand Equivalent = (Sand Reading/Clay Reading)*100 = (4.0/4.0)*100 = 100%
B. Los Angeles Abrasion Test (AASHTO T96-94)
Test 1 Counter set to 500 revolutions
Mass of oven dried CA 16 Retained on #4 Sieve = 5005.0 g
Mass of sample Retained on #8 Sieve after testing = 2455.0 g
Calculation of Percent Loss = ((5005.0 g -2455.0 g) / 5005.0 g) * 100 = 51 %
Test 2 Counter set to 500 revolutions
Mass of oven dried CA 16 Retained on #4 Sieve = 4003.8 g
Mass of oven dried CA 16 Retained on 3/8” Sieve = 1001.6 g
Total Mass Retained
5005.4 g
Mass of sample Retained on #8 Sieve after testing = 3647.4 g
Calculation of Percent Loss = ((5005.4 g -3647.4 g) / 5005.4 g) * 100 = 27 %
26
C. Sulfate Soundness Test (AASHTO T104-97)
Aggregate
FA 01
FA 01
FA 01
FA 01
FA 01
CA 16
Sieve
Mass Retained
Before Test
#50
#30
#16
#8
#4
#4
111.66 g
118.51 g
119.70 g
116.15 g
110.82 g
118.90 g
Mass Retained
After Test
110.22 g
116.23 g
115.61 g
107.80 g
81.23 g
102.54 g (Ret. #5)
Solution Used – Na2SO4 (Anhydrous Sodium Sulfate)
Temperature = 71oF
Specific Gravity = 1.174 of Na2SO4 solution
Sample calculation: using FA 01 #50 sieve
i.
Grading original sample (% Retained)
Sieve % Passing % Retained
#16
73
#30
30
43
#50
9
21
#100
1
8
ii.
Percent Passing After Test
Loss = 1.44 g
Original mass Retained = 111.66 g
Percent Passing = (1.44g/111.66g) *100 = 1.3%
iii.
Weighted Percent Loss
Original Sample Percentage * Percent Loss = 21*0.013 = 0.3%
D. Asphalt Content Ignition Method (AASHTO TP308-99)
Oven Temperature = 538oC
Original Mass of Sample = 1778 g
Mass After Burning = 1688 g
Percentage of Asphalt in Specimen = ((1778-1688)/1778)*100 = 5.0%
Loss (g)
1.44
2.28
4.09
8.35
29.59
16.36
27
E. Bulk Specific Gravity Test (AASHTO T166-93)
Temperature = 22oC
Temperature Correction Factor, K = 1.000728
Sample Mass in Air, A = 4875.6 g
Sample Mass in Water, C = 2776.8 g
Blotted Air Dry Mass, B = 4919.3 g
Calculation, Gmb = K*(A/(B-C)) = 1.000728*(4875.6/(4919.3-2776.8)) = 2.277
F. Maximum Theoretical Specific Gravity (AASHTO T209)
Mass of Type F Pycnometer filled with water @ 25.5oC, D = 22860 g
Mass of Oven Dried Sample, A = 1285 g
Mass of Container Filled with sample and water, E = 23615 g
Calculation, Gmm = A/(A+D-E) = 1285/(1285+22860-23615) = 2.425
G. Combined Bulk Specific Gravity of Aggregate Blend
Equation,
Gsb =
100
CA16/Gsb1 + FA01/Gsb2 + FA21/Gsb3 + MF/Gsb4
=
100
= 2.630
58.0/2.639 + 19.0/2.603 + 22.0/2.627 + 1.0/2.670
H. Air Voids (Va)
Va = 100*(Gmm-Gmb)/Gmm = 100*(2.425-2.277)/2.425 = 6.1%
I. Voids in Mineral Aggregate (VMA)
VMA = 100-(Gmb*Ps)/Gsb = 100 – (2.277*95)/2.630 = 17.8% Reported as 18%
J. Voids Filled with Asphalt (VFA)
VFA = 100*(VMA-Va)/VMA = 100*(17.8 – 6.1)/17.8 = 65.7% Reported as 66%
28
Appendix B
Recommendations to the Civil Engineering Department
It is recommended that the Department obtain the following items:

12” diameter brass sieves matching the existing Department ones in the following sizes:
3/8”, 1/4”, #4, #8, #30, #50, #100, #200

(2) 2500 gram aluminum pyconometers

(1) Vacuum pump capable of pulling 30 mm Hg

(4) Small C-clamps to fix and hold the Sand Equivalent Shaker in place

(1) Additional hose for use in the Sulfate Soundness back flushing process

(5) One gallon metal pots for transferring hot asphalt liquid to the batch sample

The Department should have on-hand one copy of the IDOT publication titled “Illinois
Superpave Mix Design and Bituminous Level III Update Course”

Obtain a copy of the batch weight mix design software available from IDOT. Although this is a
Lotus 1-2-3 spreadsheet type, it could be very useful for quickly adjusting aggregate
percentages and producing batch weights. Doing this operation by hand is very time consuming
and tedious. By having this program, or a similar one, the instructor or teaching assistant could
make up different mix designs for several lab groups in a relatively short period of time.
Based on my experience with mix designs, operating and setting-up the asphalt lab, and being an
assistant to Dr. Lin for the soils lab, I respectfully suggest a few things pertaining to the use of the
asphalt lab as it relates to the Department curriculum.

Introduce the students to the asphalt lab in a lower level materials course. Let them get hands
on experience with the equipment and actually making up batches of HMA. Such an
introduction could possibly take place in conjunction with the existing concrete material
course. Since the actual mix design process is rather time consuming and difficult to
understand, it is recommended that this aspect of the HMA process be included in a more
advanced pavement design course where lecture time can be dedicated to allowing the student
to more fully understand just what they are doing.
29
Appendix C
Rainhart Gyratory Compactor Problem Log
Date
Status
August 2000
Compactor and computer arrive at Engineering Building. Software that
runs the compactor already installed by manufacturer.
September 2000
Contacted by Rainhart Co. and told that the compactor needed a new
piston face. Took approximately 2 weeks to receive. Brent Vaughn
installed.
October 4, 2000
Calibrated compactor. Load cell that was provided not working properly.
Brent contacted manufacturer about problem. He recalibrated the
existing load cell himself.
October 5, 2000
Finished calibration routine.
October 23, 2000
Batched mix design sample #1. Compactor malfunctioned. The Ram
extended down to the mold but would not go up without restarting the
computer software program. The process took approximately one hour
by which time the sample was considerably colder than specifications.
Also, the angle indicator did not work on the compactor and the
computer did not register it in the data file.
October 24, 2000
Contacted Rainhart. Reviewed problems from the previous day. Talked
to Butch. Upon recommendations from Butch, I ran a second sample.
Angle display not working and neither did the Ram.
October 25, 2000
Called Rainhart. Told them of the recurrent software compactor interface
problems. Butch told me that the programmer would be contacted and
we would receive a 2nd edition of the software. The company had
updated the first version due to customer complaints but had never
bothered to inform us or send out the new version.
November 9, 2000
Received the 2nd version of the software via email. Brent installed it to
the computer. Brent and I tried to run the new version. Ram would not
even extend down to the mold. Called Rainhart and informed them of the
problem. They suggested we recalibrate. After recalibration Ram still not
working. Unable to do a test. Cancelled batching for scheduled 11/10/00.
November 10, 2000
Brent contacted Rainhart salesperson. Told him of the continued
problems. Saleperson suggested that Rainhart send out a customer
representative.
November 15, 2000
30
Brent installed another version of the software and nothing worked at all.
Over the phone, Butch said they would overnight mail Brent a new
processor board which Brent would have to install.
November 16, 2000
Received new processor board and installed. Installed new software. We
tried the machine with two asphalt samples. The angle doesn’t stay fixed
once set and the Ram extends down, hits the top of the mold and stops
the test. This is the same problem we originally had with the machine.
November 30, 2000
Brent installed another version of software. Nothing worked. Rainhart
will send a new machine and software complete with a technician to
install next week.
December 8, 2000
New compactor arrives.
December 13, 2000
Compactor and software properly working.
31
Appendix D
Student Lab Manual
Procedures for the Preparation of Hot Mix Asphalt
Test Specimens using the SuperpaveTM Method
Introduction
This manual will outline to the civil engineering student the steps necessary to prepare a hot mix
asphalt (HMA) specimen, which is used in the mix design process, using the SuperpaveTM (Superior
Performing Asphalt Pavements) mix design criteria. SuperpaveTM has been recently adopted by many
state highway departments, replacing the Marshall and the Hveem methods for asphalt mix design. The
purpose of the manual will be to outline the fundamental steps involved in the SuperpaveTM method.
Furthermore, this procedures manual shall only address preparation of the hot mix specimen. Such
related topics as aggregate blending, asphalt binder selection, material properties, and equipment
calibration are not made a part of this document. Students wishing to learn more about the total
SuperpaveTM process can contact the instructor for a list of additional resources.
Materials
The following materials will be used in the specimen production.




Performance Graded Asphalt Binder
Course Aggregate
Fine Aggregate
Mineral Filler
Equipment
The following equipment will be utilized in the specimen production.









Ovens, thermostatically controlled
Mechanical Mixer, 10 qt.
Flat bottom metal pans
Metal Scoop, spatula, and spoons
WD-40 or other light lubricating fluid
Pouring Pots, for heating asphalt
Thermometers, armored glass
Balances, 10 kg capacity
Heat resistant gloves
32



Yellow lumber crayon, for specimen identification marking
Paper disks, 6 inches, for gyratory compaction
Computer and Gyratory Compactor, for compacting and recording specimen data
Definitions
Although students should be familiar with the basic terminology of the asphalt mix design process
from lecture, the following definitions are provided for ease of reference as these are used throughout
the manual.






Asphalt Binder: the asphalt cement used to mix and bind the aggregate and mineral filler.
Course Aggregate: rock particles generally larger than the #4 sieve.
Fine Aggregate: sand, silt, and clay particles generally smaller than the #4 sieve but larger than
the #200 sieve.
Mineral Filler: dust size particles used to fill small voids in the hot mix asphalt specimen.
Gyratory Compactor: a piece of equipment used to compact the asphalt mix design specimen
at a specified pressure, angle of tilt, and revolution cycles.
Ndesign, Design Gyrations: the number of gyrations the compactor is set at for the particular
mix design specimen.
Warning: The asphalt mix design specimen procedure involves the use of heavy
aggregates and hot asphalt liquid. Students should follow all lab safety procedures
to avoid injury.
33
Procedures
The following steps outline the basic procedures in the HMA specimen production. Following these
detailed procedural steps, a flowchart is provided as a quick reference aid for student. These basic steps
are taken from Asphalt Institute. (1996). “Superpave Mix Design: Superpave Series No. 2 (SP-2).”
U.S.A.
Materials
Step 1
You will be given a batch mix design sheet by the instructor that shows the batch weights of course
and fine aggregate, asphalt, and mineral filler to be used for the HMA specimen production. Place the
individual materials in separate metal containers in the oven and heat for 2 hours at 170oC.
Step 2
After the 2- hour time period, remove materials from oven.
Mixture
Step 3
Using the provided batch sheet, place the proper amount of material into the mechanical mixing bowl.
Turn on the mixer and mix the batch until it is visually observed that all the aggregate is fully coated
with the asphalt binder. Turn off mixer.
Step 4
Remove all the specimen material from the mixer and place mixture into a shallow metal dish. Spread
mixture to an even thickness and place in the oven for 4 hours at 135oC. This time in the oven is done
to simulate short term aging that occurs during the actual production of plant generated HMA.
Compaction
Step 5
While the mixture is aging in the oven, prepare the gyratory compactor for use. A computer is
connected to the gyratory compactor via a serial port. The computer software that operates and collects
the data from the compactor is installed by the instructor and the compactor has its power to the “on”
position. For this operation, the student simply verifies the compaction pressure of 600 kpa, inclination
angle of 1.25o, and enters the Ndesign = 50 into the software at the appropriate location on the screen.
Next, take the compaction mold and place it in the oven for 60 minutes at the 135oC temperature.
34
Step 6
Remove the mixture and the compaction mold from the oven at the same time. Spray a light layer of
WD-40, or other light lubricant, to the inside of the mold. Next, place a paper disk on the bottom plate
of the mold. Then, using a scoop and spatula, place the specimen mixture into the mold, being careful
not to leave any material behind in the pan. Finally, level the specimen and place another paper disk on
top of the specimen mixture in the mold.
Step 7
Place the mold with the specimen into the gyratory compactor and click on the start button on the
computer screen. During the compaction process, the computer will monitor the specimen height,
make sure the correct compaction pressure is applied, and stop the test once the designated gyrations
have been completed.
HMA Specimen
Step 8
Once the compaction is complete, remove the mold from the center hold. Then, center the mold over
top of the extraction piston on the compactor base. Next, press the extraction button on the compactor
and extrude the specimen from the mold. Finally, let the specimen cool to room temperature, remove
the paper disks, and using a lumber crayon, mark the top of the specimen with your lab group number
for future identification.
Conclusion
The steps outlined previous illustrate the fundamental procedures necessary to produce a HMA
specimen using the Superpave criteria. The Superpave method is the most recent advance in relating
the mix design process to what actually is produced in the field. For this reason, many state highway
agencies have adopted the method. Following the prescribed steps as outlined in this manual is a key
element in producing quality HMA specimens, and therefore, increasing the accuracy of the hot mix
asphalt process from the initial design to actual production. The production of the HMA specimen is
one of the most critical elements in the Superpave Mix Design Method, and therefore, care should be
taken to ensure accurate results. The student/technician should realize that careful preparation,
attention to the details outlined in the procedures, and practicing good lab safety result in a quality
specimen and a job well done.
35
HMA Specimen
Production Flowchart
BEGIN
#1 Heat aggregates &
asphalt to specified
temperature.
#2 Remove aggregates
& asphalt from ovens.
#3 Place proportioned
aggregates & asphalt into
mixer. Mix until aggregate is
fully coated.
#4 Place mix in oven
for 4 hours at 135oC.
#5 Prepare the gyratory compactor.
Place molds in oven for 60 minutes.
#6 Remove mix & molds
from oven. Place mix into
mold.
#7 Center mold in compactor. Start
compactor. Let run to N design.
#8 Remove mold. Extract
specimen. Let cool. I.D.
specimen.
END
36
Appendix E
Asphalt Mix Design and Lab Manual for Instructors
Procedures for Developing a SuperpaveTM Mix Design
Introduction
In order for the efficient use of the civil engineering student’s time in the asphalt lab, the instructor
must complete the mix design used for making the batch specimen. This manual will cover the
essentials to the SuperpaveTM Mix Design process. The emphasis will be on developing the final batch
weights and percentages, which should be summarized on a mix design worksheet that the students
will use for making the hot mix asphalt specimen. A brief outline of materials, material testing, and
equipment will be included so that familiarity for the new instructor can be developed. For a more indepth look at these related topics, the instructor is urged to consult additional resources. This manual is
predicated on the assumption that the instructor already has a working understanding of the basic terms
and procedures involved with the asphalt mix design process, and thus much of the more basic
terminology will not be covered in this manual.
Materials
The following materials will be used in the trial batch and the hot mix asphalt (HMA) specimen
production. The aggregate designations are based on the Illinois Department of Transportation (IDOT)
Specifications.





Performance Graded Asphalt Cement (AC) Binder: AC 64-22
Course Aggregate: CA 16
Fine Aggregate: FA 01
Fine Aggregate: FA 21
Mineral Filler: Standard limestone crusher dust
Equipment
The following equipment will be utilized in the mix production and testing.











Ovens, thermostatically controlled (400o F)
Mechanical Mixer, 10 qt.
Metal pans, scoops, and spatulas
Light weight lubricating fluid
Metal pouring pots (1 gallon), for heating asphalt
Thermometers, armored glass (400o F)
Balances, 10 kg capacity (accurate to 0.1 gram)
Heat resistant gloves
Yellow lumber crayon, for specimen identification marking
Paper disks, 6 inches, for gyratory compaction
Computer and Gyratory Compactor, for compacting and recording specimen data
37


Bulk Specific Gravity tank and balance
Aluminum pycnometer (2000 gram)
Design Criteria
The following specifications are presented to highlight the primary design target values necessary for
approval of the mix under IDOT’s criteria for the IL 9.5 mm mix designation only. For other mixes,
refer to appropriate sources for the target values.
Mix Specification
Illinois 9.5mm
Equivalent Single Axle Loads (ESAL’s)
Required Density (N design)
Voids in Mineral Aggregate (VMA)
Percent (%) Air Voids (Va)
Voids Filled with Aggregate (VFA)
1 million
50
15.0%
4.0 %
65-78%
Gradation Requirements: Mix Composition
Percent Passing
Control Points
Sieve Size Minimum Maximum Minimum Maximum
12.5 mm
(1/2”)
9.5 mm
(3/8”)
4.75 mm
(#4)
2.36 mm
(#8)
75 µm
(#200)
100
100
---
90
100
90
100
24
65
---
90
16
48
32
67
4
6
2
10
Restricted Zone
Sieve Size Min
2.36 mm
47.2
1.18 mm
31.6
0.6 mm
23.5
0.3 mm
18.7
Max
47.2
37.6
27.5
18.7
Note: Superpave uses the 0.45 power chart for plotting the mix gradation. The following example
illustrates how this is accomplished for the IL 9.5 mm mix. The final mix gradation must be out of the
restricted zone and between the control points. To increase or decrease VMA change the gradation
such that the mix line moves above or below the maximum density line as indicated.
38
Procedures
Step 1…..Choose percentages of aggregate and asphalt cement for the trial batch. Guidelines are
provided below for use in the IL 9.5 mm mix.
Material
Percentage Range
CA 16
FA 01
FA 21
Mineral Filler (MF)
AC 64-22
55-60%
18-23%
20-25%
1-2%
4.5-6.0%
Step 2…..Compute the total batch percentage from the individual material gradations. The example
for the 2.36 mm sieve that follows will help with this rather tedious task.
Sieve Size
Trial Batch %
2.36 mm
CA 16 FA 01 FA 21 MF AC 64-22
57.5
4
19.0
92
22.0
77
1.5
100
5.0
NA
Total Batch Percentage (for the aggregate materials) is calculated by summing the trial percentage of
each aggregate by its gradational percent passing value.
Eg. Batch Percentage = (0.575*4) + (0.19*92) + (0.22*77) + (0.015*100) = 38.2% (2.36 mm sieve)
39
NOTE: Using this example, every sieve size that is included in the trial batch must be calculated in the
same manner so a batch percentage passing (for the aggregates) can be obtained. It should be noted
that the asphalt cement binder is simply added to the mix based on its percent weight, due to the fact it
is a liquid component of the batch.
Step 3…..Plot the total batch percentages for each sieve size computed in Step 2 on the 0.45 power
chart.
Step 4…..Verify that the batch gradation stays out of the restricted zone and in between the control
points. If it doesn’t, then choose different material percentages, recalculate the batch percentages, and
plot the new batch.
NOTE: The trial batch must be within the parameters of the 0.45 power chart in order to proceed.
Step 5…..Having successfully obtained the trial batch gradation percentages, make a batch of asphalt
mix. For specific instructions on how to make the asphalt mix refer to Appendix D Student Manual
“Procedures for the Preparation of Hot Mix Asphalt Test Specimens using the SuperpaveTM
Method”.
Step 6…..Finally, determine if the trial batch meets the IDOT specification. Follow the steps in this
manual titled Volumetrics to determine Va, VMA, and VFA. These are the last criteria that the mix
design must meet. Having met these remaining criteria, you will have successfully completed a proper
Superpave mix design.
Volumetrics
In order to determine if the trial batch meets the Design Criteria, the mix needs to be tested to
ascertain whether the target values have been met for the particular gradation chosen. The following
procedures highlight the final process of the mix design and the results will determine whether the mix
is adequate based on the criteria.

HMA Maximum Theoretical Density, Gmm
Refer to ASTM D 2041-95

HMA Bulk Specific Gravity, Gmb
Refer to ASTM D 2726-96a

Combined Bulk Specific Gravity of Aggregate Blend, Gsb
When the total aggregate trial blend consists of aggregates with different specific
gravities, which is usually the case, then the Bulk Specific Gravity for the blend must be
calculated using:
Gsb = P1 + P2 + ……+ Pn
P1 + P2 + …. + Pn
G1
G2
Gn
40
Where,

Gsb = bulk specific gravity of total aggregate blend
P1, P2, Pn = individual percentages by mass of aggregate
G1, G2, Gn = individual specific gravities of aggregate
Aggregate Percentage by Volume, Ps
Total percentage by mass of the batch that the aggregate makes up
Calculations
Using the above values, substitute into the following equations to determine VMA, Va and VFA.
Property
Target Value
VMA = 100 – (Gmb * Ps)/Gsb
15.0
Va = 100 * (Gmm – Gmb)/Gmm
4.0%
VFA = 100 * (VMA – Va)/VMA
65% - 78%
Conclusion
Creating a HMA design that meets the Superpave criteria is a time consuming and detailed task but
one that must be completed by the instructor if the asphalt lab is to run efficiently. There is more to
mix design than just mixing aggregate with hot asphalt to form a HMA specimen. Careful attention to
the details of aggregate gradation and meeting target values will ensure that the asphalt mix batched in
the lab and the test results found by the students is valid. By creating a sound mix design, the students
will gain a more advanced knowledge of the mix design process and the necessity for properly
designed pavements.
41
HMA Specimen
Production Flowchart
BEGIN
#1 Heat aggregates &
asphalt to specified
temperature.
#2 Remove
aggregates &
asphalt from ovens.
#3 Place proportioned
aggregates & asphalt into
mixer. Mix until aggregate
is fully coated.
#4 Place mix in
oven for 4 hours at
135oC.
#5 Prepare the gyratory
compactor. Place molds in
oven for 60 minutes.
#6 Remove mix &
molds from oven. Place
mix into mold.
#7 Center mold in compactor.
Start compactor. Let run to N
design.
#8 Remove mold. Extract
specimen. Let cool. I.D.
specimen.
END