PART - II
Basic Asphalt Cement and Asphalt
Unit 10: Selected Quality Control Tests for Asphalt Binder
Unit 11: Asphalt Concrete Mix Design – Marshall Method –
Unit 12: Asphalt Concrete Mix Design – Marshall Method –
Asphalt pavements are composed of skeleton of coarse and fine aggregates and a
filler of aggregate dust, asphalt cement as a binder and air voids as shown in Figures 10.1
and 10.2. Three groups of aggregates are usually used in asphalt concrete mix design.
These are coarse aggregate, fine aggregate and mineral filler.
A successful flexible pavement must have several desirable properties. These are
stability, durability, safety (skid-resistance) and economy. Because of the binding
property of asphalt cement, it is the most important constituent in asphalt concrete mix.
Quality control of asphalt cement is always required and essential for successful mix
performance. Some of these control quality tests are performance grading (PG),
penetration, softening point, ductility, flash point, thin- film oven test, solubility,
viscosity, etc. Asphalt content is a very important factor in the mix design and has a
bearing on all the characteristics of a successful pavement. Various mix design
procedures are used for finding out the “optimum” asphalt content.
Fig. 10.1: Diagram of aggregate framework with asphalt binder and air voids
VT COMPACTED WT
VV Air Voids O
VEAC Effective Asphalt Cement WEAC
VAAC Absorbed Asphalt Cement WAAC
VAgg Aggregate WAgg
VV W AC W EAC + W AAC
VTM = × 100 AC = = × 100
VT WT WT
VV + VEAC W Agg
VMA = × 100 V Agg =
VT Sp GrAgg × γ w
VFA = × 100
VEAC + VV
VT = Total volume of compacted specimen;
VV = Volume of air voids;
VEAC = Volume of effective asphalt cement;
VAAC = Volume of absorbed asphalt cement;
VAgg = Volume of aggregate;
WT = Total weight of compacted specimen;
WEAC = Weight of effective asphalt cement;
WAAC = Weight of absorbed asphalt cement;
WAgg = Weight of aggregate;
VTM = Voids in total mix, percent;
VMA = Voids in mineral aggregate, percent;
VFA = Voids filled with asphalt, percent;
AC = Asphalt content by weight of mix, percent
γw = Unit weight of water; and
Sp Gr = Specific gravity.
Fig. 10.2: Weight -volume relationships for hot mix asphalt
Among various mix design methods, Marshall method is the most popular one
because the equipment required for this method is relatively simple and inexpensive.
Selected Quality Control Tests for Asphalt Binder
Asphalt is available in a wide variety of standard types and grades. Standard
specification for the types and grades of asphalt used in pavement construction are given
in the AASHTO specifications. Asphalt cement, only, will be used in this experiment to
evaluate flash point, penetration grade and viscosity temperature relation.
Flash point indicates the temperature to which asphalt cement may be safely
heated without the danger of flash. The flash point should be measured and controlled
for safety measures. The penetration test is an empirical test used to measure the
consistency of asphalt cement at 25ºC (77ºF). Asphalt consistency can also be measured
using viscosity. Temperature-viscosity relation can be determined using rotational
viscometer. Asphalt binder should have viscosity of less than 3 Pa.s (1 Pa.s = 1000 cP)
at 135ºC for handling. For proper mixing, the viscosity of the asphalt should be 0.17 ±
0.02 Pa.s while compaction should be carried out at viscosity of 0.28 ± 0.03 Pa.s.
The purpose of the experiment is to familiarize the student with such tests and
their application in construction specifications as well as to give him a first-hand “feel”
for the characteristics of these materials. Students will be divided into groups. Each
team will perform following tests on asphalt cement samples as assigned by the
• Flash point (open cup)
• Rotational viscosity
A. Penetration (ASTM D5) (IP -49)
1. Summary of Method
The asphalt cement sample is melted and poured into a round metal
sample container where it is cooled and conditioned at a temperature of
77ºF (25ºC). A penetration needle, l aded to 100 grams, is allowed to
sink into the conditioned sample for 5 sec. The penetration number is the
depth of the penetration of the needle into the sample in units of 0.1 mm.
The softer the asphalt cement, the greater will be the penetration number.
2. Equipment and Supplies
a) Penetration apparatus
b) Sample container (55
mm dia. × 35 mm)
c) Constant temperature
f) Cleaning solvent
g) Soft cloth
Figure 10.1: Penetration Test Setup
3. Test Procedure
a) The sample will be supplied already poured into the standard container.
b) Condition the sample in the water bath at 77ºF. Remove the sample from
the water bath, carefully wipe off the water, and place the sample
container on the penetrometer platform. Record the actual bath
temperature and room temperature on a data sheet.
c) Clean the penetrometer needle with a rag dipped in solvent, and carefully
insert the needle into its holder.
d) Position the needle so that the tipjust makes contact with the sample
surface. Use the needle reflection on this surface as a guide.
e) Make sure the penetrometer dial reads zero.
f) Quickly release the needle shaft holder, and allow the needle to penetrate
into the sample for 5 seconds.
g) Measure the depth of penetration with the dial gage and record the results
in penetration units.
h) Make 3 or more determinations at points on the sample surface not less
than 10 mm from the side of the container and not less than 10 mm
apart. Clean the needle before each penetration. More than 3 readings
should be taken if any reading differs appreciably from others.
B. Flash Point (open cup) (ASTMD92) (1P-36)
1. Summary of Method
The flash point indicates the temperature to which the asphalt may be
heated safely without danger of fire ignited by an open flame. It also
gives some indication of the asphalt cement quality. The open cup flash
point is applicable only to asphalt cements. A brass cup is partly filled
with asphalt cement and heated at a prescribed rate. The flash point is the
lowest temperature at which vapors arising from the heated sample can
be ignited with a small flame.
2. Equipment and Supplies
a) 400 ml beaker
b) Laboratory oven at
300 to 325ºF
c) Flash point apparatus:
test cup, electric heater,
test flame applicator
d) Thermometer, 20 to
Figure 10.2: Flash point Setup
2. Equipment and Supplies
a) 400 ml beaker
b) Laboratory oven at 300 to 325ºF
c) Flash point apparatus: test cup, electric heater, test flame applicator
d) Thermometer, 20 to 760ºF range
3. Test Procedure
a) This method requires heating an asphalt cement to a temperature
greater than 400ºF so extreme care must be exercised to avoid painful
burns from the apparatus or spilled asphalt.
b) Support the thermometer so that the bottom of the bulb is 1/4 inch. (6
mm) above the bottom of the test cup. Swing the thermometer to the
angular position to get it out of the way temporarily.
c) Light the test flame and adjust it to the size of the comparison bead on
d) Fill a clean test cup so that the top surface (meniscus) is exactly at the
e) Apply heat initially so that the asphalt cement temperature increases at
a rate of 25 to 30ºF per min. This rate must be estimated until the
sample is soft enough so that the thermometer can be replaced to its
normal vertical position. When the temperature reaches 400ºF,
decrease the rate of temperature rise between 9 to 11ºF per minute.
f) Beginning at 450ºF, apply the test flame by passing it over the sample
surface with a smooth continuous motion. In 1 second time interval.
Make a test flame pass at every 5ºF interval (450ºF, 455ºF, 460ºF ...)
until the sample is producing enough inflammable vapor so that a
flash flame is observed on the surface of the sample. Record the
temperature at which a flash is observed as the flash point.
g) Using gloves to protect your hand, pour the hot sample into a waste
container provided. The instructor will demonstrate how then to clean
the cup so that it is ready for the next test.
C. Rotational Viscometer (ASTM D4402)
A rotational viscosity test is used to determine the flow characteristics of the
asphalt binder to provide some assurance that it can be pumped and handled at the hot
mixing facility. A rotational coaxial cylinder viscometer as shown in Figure 10.3 and
described in ASTM D4402, Standard Method for Viscosity Determinations of Unfilled
Asphalts Using the Brookfield Thermosel apparatus, is necessary to evaluate the various
types of asphalt binders. Unlike capillary tube viscometers, the rotational viscometers
have larger clearances between the components and, therefore, are applicable to modified
and unmodified asphalts.
The rotational viscometer automatically calculates the viscosity at the test
temperature. The rotational viscosity is determined by measuring the torque required to
maintain a constant rotational speed of a cylindrical spindle while submerged in an
asphalt binder sample at a constant temperature (Figure 10.4). This torque is directly
related to the binder viscosity, which is calculated automatically by the viscometer.
Since this binder viscosity is used to ensure that the asphalt is fluid enough to pump and
mix with aggregate, it is measured on original or “tank” asphalt. The viscometer can
also be used to develop temperature- viscosity charts for estimating mixing and
compaction temperatures for use in mixture design.
1. Specimen Preparation. Approximately 30 grams of binder are heated in an oven
(below 150ºC) until fluid. The sample should be stirred occasionally during heating to
remove entrapped air. Asphalt is weighed into the preheated sample chamber. The
amount of asphalt used is typically 8 to 11 grams and varies with the size of spindle. The
sample chamber containing the binder sample is placed in the preheated thermo-
container, the preheated spindle is lowered into the sample, and the binder is ready to test
when the temperature stabilizes, usually within 30 minutes.
Figure 10.3: Rotational Coaxial Cylinder Viscometer
Figure 10.4: Cylindrical Spindle and Thermo-cell
2. Test Procedure. The apparatus used to measure rotational viscosity consists of two
parts: Brookfield viscometer and the ThermoselT M system. The Brookfield viscometer
consists of a motor, spindle, control keys, and digital readout. The motor powers the
spindle rotation through a torsional spring. The spring is wound as the torque increases.
The torque in the spring is measured by a rotary transducer. For specification testing, the
motor is set to operate at 20 rpm.
The spindle resembles a plumb bob and spindle rotation is resisted by the viscous
binder. Many spindles are available for the Brookfield apparatus; the proper spindle is
selected based on the viscosity of the binder being tested.
The ThermoselT M system consists of the sample chamber, thermo-container, and
temperature controller. The sample chamber is a stainless steel or aluminum cup; the
thermo-container holds the sample chamber and consists of electric heating elements that
are used to maintain or change the test temperature. The controller allows the test
temperature to be set at the required 135ºC.
To function properly, the viscometer and thermo-container must be leveled using
bubble levels and leveling screws. Control keys are used to input test parameters such as
spindle number, set rotational speed, and turn the motor on and off. The spindle is
coupled with the viscometer.
A waiting period of about 15 minutes may be needed to reach a uniform sample
temperature of 135ºC. During this period, the viscometer motor is turned on and the
viscosity reading and the percent torque can be observed on the digital display. As the
temperature equalizes, the viscosity reading will stabilize and test results are recorded.
The digital display is set to show the information that is needed for the report: viscosity,
test temperature, spindle number, and speed. These viscosity readings are recorded at 1-
It may be desirable to determine the binder viscosity at temperatures other than
135ºC. For example, most agencies use equiviscous temperatures for mixing and
compaction during mix design. Regardless of the grade used, the binder temperatures
are adjusted to obtain the same specified range of binder viscosity when mixing with
aggregate and compacting specimens in the laboratory. To accomplish this, the
ThermoselT M controller is reset to a higher desired temperature (e.g. 165ºC), and the test
is performed as before.
3. Data Analysis. The viscosity at 135ºC is reported as the average of three readings.
The digital output of some rotational viscometers is in units of centipoises (cP) while the
Superpave binder specification uses Pascal-seconds, Pa.s. The conversion used is 1000
cP = 1 Pa.s. Therefore, to obtain the viscosity in Pa.s, the Brookfield viscosity in cP is
multiplied by 0.001. As mentioned previously, the test temperature, spindle number, and
speed are also required report items. The Superpave binder specification requirement of
a maximum of 3 Pa.s is applied at the discretion of the specifying agency.
1. Compare the results of your tests for penetration and flash point with the
specification given in ASTM D946-82, given in Appendix C. Which category of
asphalt cement was used in the test? What other tests are specified by D946.
2. Plot the relation between viscosity and temperature (135ºC and 165ºC). What
would be the recommended mixing t mperature? What is the recommended
3. How does viscosity affect mixing and compaction? How would you select
mixing and compaction temperature?
Asphalt Concrete Mix Design - Marshall Method
Part I: Sample Preparation
The overall procedure for mixture design always begins with acceptance tests
performed on the aggregates and asphalt cement considered for the design. If the
acceptance tests on the aggregates and asphalt cement pass, the procedure included in
ASTM D1559, Resistance to Plastic Flow of Bituminous Mixtures Using the Marshall
Apparatus, can be performed on the mixture. The procedure that follows is appropriate
only for paving grade asphalt cements (graded according to penetration or viscosity)
used with maximum size aggregates not exceeding 1 inch. Since the mold diameter to
maximum particle size ratio should exceed at least 4, a 1- inch diameter particle is the
largest aggregate size permitted in the 4- inch Marshall mold.
The objective of this experiment is to expose students to the process of
optimizing asphalt concrete mix used for highway construction as part of mix design
In this experiment, students will prepare different asphalt concrete mixes by
varying the asphalt content in each mix in accordance with the Marshall method of mix
design. In the next lab session, these specimens will be tested to obtain the optimum
asphalt content by performing the Marshall test for stability and flow.
In this experiment, students are reorganized into five groups.
11.4 Material and Equipment
1. Asphalt, aggregate, sand
2. Sieve analysis equipment
3. Pans and mixing bowl
5. Compaction pedestal
6. Compaction hammer
7. Marshall mo lds.
Figure 11.1: Marshall Compacter
STEP 1. Aggregate Evaluation
1-1. Determine acceptability of aggregate for use in hot mix asphalt (HMA)
construction; tests often performed include Los Angeles abrasion, sulfate
soundness, sand equivalent, presence of deleterious substances, polishing,
crushed face count, and flat and elongated particle count.
1-2. If material is acceptable in Step 1-1, then perform other required aggregate tests:
gradation, specific gravity, and absorption.
1-3. Perform blending calculations as described in class. As a suggested beginning
point, plot the specification midband gradation on a FHWA 0.45 power gradation
chart and see how close the midband gradation comes to the maximum density
line. If it is too close, the VMA is likely to be too low. The target gradation
should be adjusted to deviate from the maximum density line, especially on the
no. 8 sieve. VMA increases as the gradation lines move away from the
maximum density line plot either up or down. A good beginning point for
estimating percentages of aggregates in a blend can be made by using the target
percentage passing the Nos. 8 and 200 sieves and estimating the quantities of
each aggregate required to meet those two percentages. A full gradation check
must then be made to check that the percentages passing for other sieve sizes are
met. Aggregate blending is discussed in detail in class.
1-4. Prepare a specimen weigh-out table by multiplying the percent aggregate
retained between sieves times an aggregate weight of approximately 1150g, then
determine the cumulative weights starting with the material passing the No. 200
STEP 2. Asphalt Cement Evaluation
2-1. Determine appropriate asphalt cement grade for type and geographical location
of mixture being designed.
2-2. Secure viscosity information at 140ºF and 275ºF and verify that specification
properties are acceptable for flash point, viscosity, penetration, ductility,
solubility, and specified residue tests after heating.
2-3. Determine asphalt cement specific gravity and plot viscosity data on a
temperature- viscosity plot.
2-4. Determine the ranges of mixing and compaction temperatures from the
temperature- viscosity plot:
1. Mixing temperature should be selected to provide a viscosity of 170 ± 20
2. Compaction temperature should be selected to provide a viscosity of 280 ±
STEP 3. Preparation of Marshall Specimens
Prepare Marshall Specimens using the procedures given in Steps 3-1 thru 3-7 for
individual specimens. As an alternate, HMA for a desired asphalt content can be
prepared in bulk to produce the required number of compacted Marshall specimens and
to provide a sample for determination of maximum (Rice) specific gravity.
3-1. Dry and sieve aggregates into sizes (preferably individual sizes) and store in
clean sealable containers. Separate enough material to make 18 specimens of
approximately 1150 g each. Minimum aggregate and asphalt cement
requirements to prepare one series of test specimens of a given gradation are 50
pounds and one gallon, respectively.
3-2. Weigh out aggregate for 18 specimens placing each in a separate container and
heat to mixing temperature determined in Step 2-4. However, the total aggregate
weight should be determined as discussed in Step 3-3.
3-3. It is generally desirable to prepare a trial specimen prior to preparing all
aggregate batches. Measure the height of the trial specimen (h1 ) and check
against height requirements for Marshall specimens: 2.50 inch ± 0.20 inch. If the
specimen is outside this range, adjust quantity of aggregate included in a
specimen using the following formula:
Q= × 1150 g
Q = weight of aggregate to produce a specimen 2.5 inches tall, g; and
h1 = height of trial specimen, inches.
3-4. Heat sufficient asphalt cement to prepare a total of 18 specimens. Three
compacted specimens each should be prepared at five different asphalt contents.
Asphalt contents should be selected at 0.5 percent increments with at least two
asphalt contents above “optimum” and at least two below “optimum”. Three
loose mixture specimens should be made near the optimum asphalt content to
measure Rice specific gravity or theoretical maximum density (Gmm). After
calculating the effective specific gravity of the aggregate Gse, the maximum
specific gravity for the other four asphalt contents can be calculated using the
1 − Pb
1 − Pb P
Gse = Effective specific gravity of aggregate;
Pb = Asphalt content;
Gb = Specific gravity of asphalt cement; and
Gmm = Maximum specific gravity of mixture.
3-5. Review appropriate specifications to determine number of blows/side and type of
compaction equipment required for compaction of Marshall specimens.
3-6. Remove the hot aggregate, place it on a scale, and add the proper weight of
asphalt cement to obtain the desired asphalt content.
3-7. Mix asphalt cement and aggregate until all the aggregate is coated. It is helpful
to work on a heated table. Mixing can be by hand, but a mechanical mixer is
3-8. Check temperature of freshly mixed material; if it is above the compaction
temperature, allow it to cool to compaction temperature; if it is below
compaction temperature, discard the material and make a new mix.
3-9. Place a paper disc into an assembled, preheated Marshall mold and pour in loose
HMA. Check the temperature. Spade the mixture with a heated spatula or
trowel 15 times around the perimeter and 10 times over the interior. Remove the
collar and mound materials inside the mold so that the middle is slightly higher
than the edges. Attach the mold and base plate to the pedestal. Place the
preheated hammer into the mold, and apply the appropriate number of blows to
the top side of the specimen.
3-10. Remove the mold from the base plate. Place a paper disc on top of the specimen
and rotate the mold 180º so that the top surface is on bottom. Replace the mold
collar and attach the mold and base plate to the pedestal. Place the hammer in
the mold and apply the same number of blows to the opposite side of the
3-11. Remove the paper filters from the top and bottom of specimens. Cool the
specimens and extrude from the mold using a hydraulic jack. Place identification
marks on each specimen with an alphanumeric code using a grease pencil.
Allow specimens to sit at room temperature overnight before further testing.
3-12. Determine the bulk specific gravity for each specimen by weighing in air.
Submerge the samples in water and allow to saturate prior to getting submerged
weight for at least 2 mins. Remove the sample and weigh in air in saturated
surface dry (SSD) condition. This test is conducted in accordance with
3-13. Measure the Rice specific gravity on the loose HMA mix samples in accordance
with AASHTO T209 (ASTM D2041). This specific gravity is required for voids
analysis. If the mix contains absorptive aggregate it is recommended to place the
loose mix in an oven (maintained at the mix temperature) for at least 4 hours so
that the asphalt cement binder is completely absorbed by the aggregate prior to
testing. Keep the mix in a covered container while in the oven. If the test is run
in triplicate on the mix containing near optimum asphalt content, average the
three results, calculate the effective specific gravity of the aggregate, and then
calculate the Rice specific gravity or Gmm for the remaining mixes with different
asphalt contents. If one Gmm test is conduc ted on each mix containing a different
asphalt content, then calculate the effective specific gravity, and then calculate
the Gmm values using the average for all five mixes.
Asphalt Concrete Mixing Design – Marshall
Part II: Sample Testing
In this test, the students will carry out the Marshall tests for stability and flow of
asphalt specimens prepared in Unit 10 and thus determine the effect of asphalt content on
stability and flow.
12.2 Equipment and Supplies
a) Marshall Testing Machine and
b) Water bath
Figure 12.1: Marshall Testing
Machine and Flow Meter.
STEP 1. Marshall Stability and Flow Test
1-1. Heat the water bath to 140ºF and place specimens to be tested in the bath for at
least 30 but not more than 40 minutes. Place specimens in the bath in a staggered
manner to ensure that all specimens have been heated for the same length of time
before testing. Use a waterbath large enough to hold all specimens prepared for
the mixture design.
1-2. After heating for the required amount of time, remove a specimen from the bath,
pat with towel to remove excess water, and quickly place in the Marshall testing
1-3. Bring the loading ram into contact with the testing head. Zero the pens if using a
load-deformation recorder or zero flow gauge, and place the gauge on the rod of
the testing head. Apply the load at 2 inches/minute until maximum load is
reached. When load just begins to decrease, remove the flow meter, stop ram
movement, and record the stability (maximum load) in lbs and flow in 0.01
inches. Testing should be completed within 1 minute from the time the specimen
is removed from the bath.
1-4. Repeat Steps 1-2 and 1-3 until all specimens have been tested being careful to
1. The total elapsed time between removing a specimen from the water bath and
the maximum load applied is less than 60 seconds.
2. The total time in the water bath for each set of 3 specimens is the same and is
between 30 and 40 minutes.
STEP 2. Density and Voids Analysis
2-1. For each specimen, use the bulk specific gravity (Gm b) and the Rice Specific
Gravity (Gmm ) to calculate the percent voids or VTM.
VTM = 1 − mb 100
2-2 Calculate the density of each Marshall specimen as follows:
Density (pcf) = Bulk Specific Gravity (Gmb) × 62.4
2-3 Calculate the VMA for each Marshall specimen using the bulk specific gravity of
the aggregate (Gsb ), the bulk specific gravity of the compacted mix (Gmb), and the
asphalt content by weight of total mix (Pb ):
G (1 − Pb )
VMA = 100 1 − mb
2-4. Calculate the VFA (voids filled with asphalt) for each Marshall specimen using
the VTM and VMA as follows:
VMA − VTM
VFA = 100
STEP 3. Tabulating and Plotting Test Results
3-1. Tabulate the results from testing, correct the stability values for specimen height
(ASTM D1559), and calculate the average of each set of 3 specimen.
3-2. Prepare the following plots:
§ Asphalt content versus density (or unit weight);
§ Asphalt content versus Marshall stability;
§ Asphalt content versus flow;
§ Asphalt content versus air voids (or VTM);
§ Asphalt content versus VMA; and
§ Asphalt content versus VFA.
3-3. Review the plots for the following trends:
§ Stability versus asphalt content can follow two trends:
(a) Stability increases with increasing asphalt content, reaches a peak, and
(b) Stability decreases with increasing asphalt content and does not show a
peak. This curve is common for some recycled HMA mixtures.
§ Flow should increase with increasing asphalt content.
§ Density increases with increasing asphalt content, reaches a peak, and then
decreases. Peak density usually occurs at a higher asphalt content than peak
§ Percent air voids should decrease with increasing asphalt content.
§ Percent VMA decreases with increasing asphalt content, reaches a minimum,
and then increases.
§ Percent VFA increases with increasing asphalt content.
STEP 4. Optimum Asphalt Content Determination
4-1. The following method is commonly used to determine the optimum asphalt
content from the plots (Asphalt Institute Method in MS-2):
1. Determine (a) Asphalt content at maximum stability
(b) Asphalt content at maximum density
(c) Asphalt content at mid point of specified air void range
(4.5 percent typically).
2. Average the three asphalt contents selected above.
3. For the average asphalt content, go to the plotted curves and determine the
§ Stability (min 1800 lb for heavy traffic);
§ Flow (8-14 (units of 0.01 in));
§ Air voids (3-6%); and
§ VMA (13% min).