Effects of Heat and Air On Asphaltic Materials (Thin-Film Oven Test)
Effects of Heat and Air On Asphaltic Materials (Thin-Film Oven Test)
Effects of Heat and Air On Asphaltic Materials (Thin-Film Oven Test)
for the
Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
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considered capable of competent and objective testing and sampling. circular shelf in a vertical position at a point equidistant from
the center and outer edge of the shelf. The bottom of the
5. Apparatus thermometer bulb shall be 40 mm [1.5 in.] above the top of the
5.1 Oven—The oven shall be electrically heated and shall shelf. The thermometer shall be radially centered over a sample
conform to the performance requirements of Specification container position. If a PRT or RTD is used for determining the
E145, Type IB (Gravity-Convection), for operating tempera- test temperature, it shall be independent of the oven tempera-
tures up to 180°C [356°F]. During the tests for compliance to ture control system and the tip of the measuring sensor shall be
Specification E145 requirements, the oven shelf, properly positioned 40 mm [1.5 in.] above the top of the shelf and
centered as described in 5.1.2 shall be in place and rotating. centered over the arc of the rotating pans. Thermometric
5.1.1 Construction—The oven shall be rectangular, and each devices shall be calibrated when initially installed, and their
interior dimension (exclusive of space occupied by the heating accuracy at 163°C [325°F] shall be verified at least annually
element) shall be a minimum of 330 mm [13 in.] and a thereafter.
maximum of 535 mm [21 in.]. The oven shall have, in front, a 5.3 Container—Cylindrical pans, 140 6 1 mm [5.5 6 0.04
tightly fitted hinged door, which shall provide a clear opening in.] in inside diameter and 9.5 6 1.5 mm [3⁄8 6 1⁄16 in.] deep
substantially the same as the interior height and width of the with a flat bottom. Fifty millilitres of the sample in this size
oven. The door may contain a window with dimensions of at container give a film thickness of approximately 3.2 mm [1⁄8
least 100 by 100 mm [4 by 4 in.] and with two sheets of glass in.]. Pans shall be made of stainless steel and shall have a metal
separated by an air space, through which a vertical thickness of approximately 0.64 mm [0.025 in.].
thermometer, located as specified in 5.2, may be read without
NOTE 2—Pans have a tendency to become warped or bent with use.
opening the door; or the oven may be provided with an inner Although tests indicate that a small amount of warping does not
glass door, through which the thermometer may be observed on significantly affect results, frequent inspection to eliminate warped or
opening the outer door momentarily. The oven shall be damaged pans is advisable. The indicated metal thickness has been found
adequately ventilated by convection currents of air and for this to provide adequate rigidity without excessive weight. Stainless steel pans
manufactured from 0.6-mm thick [No. 24] stainless sheet gauge steel
purpose shall be provided with openings for the entrance of air
comply with the recommended thickness. Pans made from 0.48 mm-thick
and for the exit of heated air and vapors. Openings may be of [No. 26] stainless sheet gauge metal are also acceptable but have a greater
any size and arrangement provided the requirements of Speci- tendency to warp during use.
fication E145, Type IB, are met. 5.4 Balance—A balance conforming to the requirements of
5.1.2 Rotating Shelf—The oven shall be provided with a guide D4753, Class G2.
single metal circular shelf having a minimum diameter of 250
mm [9.8 in.] and a maximum diameter of 450 mm [18 in.]. The 6. Preparation of Oven
shelf construction shall be such that it provides a flat surface
for support of the containers without blocking all air circulation 6.1 Ensure that the thermometric device tip is positioned 40
through the shelf when the containers are in place. The shelf mm [1.5 in.] above the top of the shelf and centered over the
shall be suspended by a vertical shaft and centered with respect arc of the rotating pans.
to the horizontal interior dimensions of the oven and shall be 6.2 Ensure the oven is level so that the shelf rotates in a
provided with a mechanical means of rotating it at the rate of horizontal plane. The maximum tilt during rotation shall not be
5.5 6 1.0 r/min. The preferred vertical position for the shelf is more than 3° from the horizontal.
150 mm [6 in.] above the bottom of the oven (exclusive of
6.3 Preheat oven for a minimum of two hours prior to
space occupied by the heating element), and the shelf shall be
testing, with the control setting adjusted to the setting that will
located as close to this position as permitted by compliance
be used during the test. The setting shall be selected such that
with the requirements of 5.2 regarding thermometer placement.
when the oven is fully loaded, the oven will equilibrate at 163.0
The shelf shall be constructed or marked in such a way that the
6 1°C [325 6 2°F].
sample containers can be placed in the same position during
each test. There shall be a minimum of two and a maximum of NOTE 3—Removing sample containers will affect convection patterns in
six sample container positions. Each sample container position the oven, and may cause the temperature reading to change from the
desired reading. This is normal, and occurs because the thermometric
shall be symmetrical with respect to the shaft and to any holes device is not in the same location as the temperature control sensor.
in the shelf. The number of sample container positions shall be Replacing the containers should cause the temperature reading to return to
the maximum that will fit on the shelf without violating the the original reading.
above requirements and without excessive overhang.
5.2 Thermometric Device—An ASTM Loss on Heat Ther- 7. Preparation of Samples
mometer having a range from 155 to 170°C and conforming to 7.1 Place sufficient material for the test in a suitable
the requirements for Thermometer 13C, as prescribed in container and heat to a fluid condition. Extreme care should be
Specification E1, or a Grade A platinum resistance taken so that there is no local overheating of the sample and
thermometer, commonly known as a PRT or an RTD (or both), that the highest temperature reached is not more than 163°C
conforming to Specification E1137/E1137M, connected to a [325°F]. Stir the sample during the heating period, but avoid
meter readable to 0.1°, and verified accurate at 163°C [325°F], incorporating air bubbles in the sample. Transfer 50 6 0.5 g
shall be used for determining the test temperature. The 13C into each of two or more tared containers meeting the require-
thermometer, if used, shall be supported from the shaft of the ments of 5.3.
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7.2 At the same time, pour a portion of the sample into the combined residues thoroughly, in a semi fluid state, until
containers specified for measurement of original asphalt prop- homogenous. If needed, heat the combined residues in the
erties. Complete the tests by appropriate ASTM Test Methods covered metal container in an oven at a temperature not
D5, D2170, or D2171. exceeding 163°C [325°F]. Complete the tests on residue by
7.3 If the quantitative value of the mass change is desired, appropriate ASTM Test Methods D5, D2170, or D2171 within
cool the samples for the oven test to room temperature and 72 h of performing this test.
determine the mass of each sample separately to the nearest NOTE 7—Care should be taken if the sample is reheated, since excessive
0.001 g. If the mass change is not required, allow the samples reheating can affect the apparent severity of the test.
to cool to approximately room temperature before placing in 9. Report
the oven as directed in 8.1.
9.1 Report the values of the original asphalt properties
8. Procedure measured in 7.2 and the residue property values as measured in
8.3. Viscosity change may also be expressed as the ratio of the
8.1 With the oven preheated and adjusted as described in residual asphalt viscosity to the original asphalt viscosity.
6.3, quickly place the asphalt samples in the predetermined Penetration change is evaluated as the penetration of the
sample container positions on the circular shelf (Note 4 and residue expressed as the percentage of the original penetration.
Note 5). Fill any vacant positions with empty sample
containers, so that every sample container position is occupied. 9.2 Report ductility or other test results in accordance with
Close the oven door and start rotating the shelf. Maintain the the appropriate ASTM test methods.
specified temperature range for 5 h after the sample has been 9.3 When determined, report the average mass change of the
introduced and the oven has again reached that temperature. material in all containers as mass percent of the original
The 5-h period shall start when the temperature reaches 162°C material. A mass loss shall be reported as a negative number,
[323°F] and in no case shall the total time that a sample is in while a mass gain shall be reported as a positive number.
the oven be more than 51⁄4 h. At the conclusion of the heating NOTE 8—This test can result in either a mass loss or a mass gain. During
period, remove the samples from the oven. If the mass change the test, volatile components evaporate (causing a decrease in mass), while
is not being determined, proceed in accordance with 8.3. If the oxygen reacts with the sample (causing an increase in mass). The
mass change is being determined, cool to room temperature, combined effect determines whether the sample has an overall mass gain
determine the mass to the nearest 0.001 g, and calculate the or an overall mass loss. Samples with a very low percentage of volatile
components will usually exhibit a mass gain, while samples with a high
mass change on the basis of the asphalt in each container (Note percentage of volatile components will usually exhibit a mass loss.
6). NOTE 9—If a skin formation is noted during testing, it should be
included in the report.
NOTE 4—Materials having different mass change characteristics should
not generally be tested at the same time due to the possibility of 10. Precision and Bias
cross-absorption.
NOTE 5—This test method does not prohibit placing an asphalt sample 10.1 Criteria for judging the acceptability of the viscosity at
in the position under the mercury thermometer. However, it is recom- 60°C [140°F] and 135°C [275°F], viscosity ratio at 60°C
mended that this position not be used for a sample, and that an empty pan [140°F], change in penetration at 25°C [77°F], ductility at
remain in this position, in order to minimize the risk associated with
thermometer breakage.
15.6°C [60°F] (average of three measurements), and mass
NOTE 6—When complete tests cannot be made in the same day, and if change test results obtained by this method are given in Table
the mass change is being determined, determine the masses of the residues 1. The figures given in Column 2 are the standard deviations
and store them overnight before reheating. If the mass change is not being that have been found to be appropriate for unmodified materi-
determined, transfer the residue to the 240-mL [8-oz] container as als and the conditions of test described in Column 1. The
described in 8.3 before storing overnight.
figures given in Column 3 are the limits that should not be
8.2 After determining the mass of the samples, place them exceeded by the difference between the results of two properly
on a refractory-board and then on the shelf of the oven conducted tests. The figures given in Column 4 are the
maintained at 163°C [325°F]. Close the oven and rotate the coefficients of variation that have been found to be appropriate
shelf for 15 min and immediately proceed as described in 8.3. for the materials and conditions of test described in Column 1.
8.3 Remove each pan individually and transfer the contents The figures given in Column 5 are the limits that should not be
by pouring and scraping into a seamless metal container of exceeded by the difference between the results of two properly
approximately 240-mL [8-oz] capacity. Remove substantially conducted tests expressed as a percent of their mean.
all of the material from the pans by scraping with a suitable 10.2 Bias—The bias for this test method cannot be deter-
tool such as a spatula or putty knife. While the residue is being mined because no material with an accepted reference value is
removed from each pan, the oven door shall remain closed, available.
with the heater power on, and the remaining samples rotating
on the shelf. The final pan shall be removed from the oven 11. Keywords
within 5 min of the removal of the initial pan. Stir the 11.1 aging; asphalt cement; Thin-Film Oven Test (TFOT)
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TABLE 1 Precision of Test on TFOT Residue
Standard Coefficient of Variation Acceptable Range of
Acceptable Range of
Material and Type Index Deviation (percent of Two Results (percent
Two Results (d2s)
(1s) mean) (1s%) of mean) (d2s%)
Single-operator precision:
Percentage of retained penetration 1.43 4.0 ... ...
Change in mass percentage:
Not more than 0.4 % (max) 0.014 0.04 ... ...
Greater than 0.4 % ... ... 2.9 8.0
Viscosity at 60°C [140°F] ... ... 3.3 9.3
Viscosity at 135°C [275°F] ... ... 2.0 5.7
... ... 5.6 16.0
viscosity at 60°C f 140°F g after test
Ratio:
viscosity at 60°C f 140°F g before test
APPENDIX
(Nonmandatory Information)
X1.1 Research conducted in 1992 indicates that the severity place of the test thermometric device described in 5.2.
of this test is affected by thermometer position, number of
sample containers used, oven geometry and shelf geometry. X1.3 Recommended Oven Construction—The oven shall be
These factors were inadequately controlled in earlier versions rectangular with interior height of 380 mm [15 in.], interior
of this test, and the 1993 revision addresses these issues. width of 480 mm [19 in.], and interior depth of 460 mm [18
Factors relating to oven and shelf geometry are being handled in.]. These dimensions are exclusive of space occupied by the
in this appendix as a recommendation rather than a heating elements and the door. All heating elements shall be
requirement, in order to avoid obligating labs to purchase new located in the bottom of the oven. The oven shall have, in front,
ovens. a tightly fitted hinged door, which shall provide a clear opening
substantially the same as the interior height and width of the
X1.2 Recommended Oven Type and Control—The oven oven. The door shall contain a window with dimensions of at
shall be electrically heated and shall conform to the perfor- least 200 mm [8 in.] high and 300 mm [12 in.] wide. The
mance requirements of Specification E145, Type IB (Gravity- window shall consist of two sheets of glass separated by an air
Convection), for operating temperatures up to 180°C [356°F]. space, through which a vertical thermometer, located as speci-
During the tests for compliance to Specification E145 fied in 5.2, may be read without opening the door. The top of
requirements, the oven shelf shall be in place and rotating, with the test chamber shall have exactly two vent openings, one on
an empty sample container in each of the four sample container each side of the oven. Each opening shall have a diameter of
positions. The oven temperature shall be regulated by a 25 mm [1 in.]. Each opening shall be located 75 mm [3 in.]
proportional temperature controller, using a platinum resis- from the side, and centered between the front and back of the
tance temperature detector or a thermistor sensor mounted 25 test chamber. These openings shall remain unobstructed when-
mm [1 in.] below the roof of the test chamber, and beneath one ever the oven is in operation. There shall be no openings on the
of the vent holes. This temperature sensor shall not be used in sides of the test chamber. Other openings may be of any size
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and type provided the requirements of Specification E145, X1.4 Recommended Rotating Shelf—The oven shall be
Type IB, are met. provided with a single cast aluminum shelf, with a diameter of
NOTE 1—There is no direct SI equivalent for screw threads and drill holes, therefore they have been omitted. The controlling dimensions of the screw
and the drill hole, however, have been converted to SI units.
FIG. X1.1 Recommended TFOT Shelf
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340 mm [13.5 in.], as shown in Fig. X1.1. The top of the shelf horizontal interior dimensions of the test chamber. The shelf
shall have four raised ribs which define four sample container shall be provided with a mechanical means of rotating it at a
positions. Fig. X1.2 shows an overhead view of the shelf, with rate of 5.5 6 1.0 r/min. The vertical position of the shelf shall
four sample containers properly positioned. The shelf shall be be 150 mm [6 in.] above the bottom of the oven (exclusive of
suspended by a vertical shaft and centered with respect to the space occupied by the heating elements).
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