ASTM D7944-22

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it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7944 − 15 D7944 − 22
Standard Practice for
Recovery of Emulsified Asphalt Residue Using a Vacuum
Oven
This standard is issued under the fixed designation D7944; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice is suitable for recovery of the residue of emulsified asphalts composed principally of a semisolid or liquid
asphaltic base, water, and an emulsifying agent. Asphalt base may be pre-modified with polymeric modifiers or latex polymer
modifiers may be incorporated into the emulsified asphalt through co-milling or post emulsified asphalt production blending.
1.2 The text of this standard references notes and footnotes which provide explanatory material. These notes and footnotes
(excluding those in tables and figures) shall not be considered as requirements of the standard.
1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1.4 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D244 Test Methods and Practices for Emulsified Asphalts
D7175 Test Method for Determining the Rheological Properties of Asphalt Binder Using a Dynamic Shear Rheometer
D7405 Test Method for Multiple Stress Creep and Recovery (MSCR) of Asphalt Binder Using a Dynamic Shear Rheometer
2.2 AASHTO Standards:
R28R 28 Accelerated Aging of Asphalt Binder Using a Pressurized Aging Vessel (PAV)
PP 72 Standard Practice for Recovery Residue from Emulsified Asphalt Using Low-Temperature Evaporative Techniques
3. Summary of Practice
3.1 A sample of emulsified asphalt is spread in a thin film on a silicone rubber mat and conditioned in a vacuum oven or other
suitable vacuum chamber to remove the water.
This practice is under the jurisdiction of ASTM Committee D04 on Road and Paving Materials and is the direct responsibility of Subcommittee D04.42 on Emulsified
Asphalt Test.
Current edition approved Oct. 1, 2015July 1, 2022. Published December 2015August 2022. Originally approved in 2015. Last previous edition approved in 2015 as
D7944 – 15. DOI: 10.1520/D7944-15.10.1520/D7944-22.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
Available from American Association of State Highway and Transportation Officials (AASHTO), 444 N. Capitol St., NW, Suite 249, Washington, DC 20001,
http://www.transportation.org.
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D7944 − 22
4. Significance and Use
4.1 This practice can be used to obtain residues of emulsified asphalts. The residue may be used for further testing.
4.2 As approximately 5 g of residue is typically obtained, limited testing is possible.
NOTE 1—Rheological characterization as described in Test Methods D7175 and D7405 are suitable test methods. Additional test methods are being
developed suited to the small amounts of residue obtained.
5. Apparatus
5.1 Silicone rubber mat approximately 30 by 20 by 0.3 cm (approximately 12 by 9 by 0.15 in.), minimum of 40A durometer.
5.2 Supports for Silicone Rubber Mat—Provide adequate support of the silicone rubber mat during draw down draw-down of the
film, while transporting to the vacuum oven or other suitable vacuum conditioning chamber, and while recovering the emulsified
asphalt residue. The procedure uses two separate supports, one at ambient temperature for draw down draw-down and transfer, and
a second to support the silicone rubber mat and emulsified asphalt during residue recovery. Adequate supports include but are not
limited to a metal plate or tile with dimensions that are larger than the silicone rubber mat.
5.3 Draw down Draw-down applicator with the ability to draw down a wet film approximately 0.38 mm (15 mils) in thickness.
(See Fig. 1.)
5.4 Vacuum oven or any suitable heated pressure reduction vessel, capable of maintaining a temperature of 60 6 5°C5 °C (140
6 10°F)10 °F) and holding a vacuum of 1300 6 500 Pa (0.4 6 0.2 inHg) in. Hg) absolute pressure for the specified test time.
5.5 Tool capable of removing the emulsified asphalt residue from the silicone rubber mat after recovery without the use of heat
or chemical reagents. Recommended tools include a metal spatula to scrape off the material or rolling by a glass rod. Use removal
tools with dimensions suitable for the area of the drawn down emulsified asphalt film.
FIG. 1 (a) Example of Thin Film Applicator (a) and Applicator; (b) Emulsified Asphalt Film Produced After Draw Down (b)Draw-Down
The sole source of supply of the apparatus (referred to as “Silicone Rubber Sheeting” in catalog) known to the committee at this time is McMaster Carr, 200 New Canton
Way, Robbinsville, NJ 08691-2343, www.mcmaster.com. If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your
comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.
The sole source of supply of the apparatus (8-Path Known sources for applicators can be found at www.gardco.com (8 Path Wet Film Applicator) known to the committee
at this time is Paul N. Gardner Company, Inc., 316 N.E. First Street, Pompano Beach, FL 33060, www.gardco.com. and BYK Gardner USA, www.directindustry.com (stainless
steel film applicator). If you are aware of alternative suppliers, please provide this information to ASTM International Headquarters. Your comments will receive careful
consideration at a meeting of the responsible technical committee, which you may attend.
D7944 − 22
6. Reagents and Materials
6.1 Cleaning agent, capable of removing residual asphalt and other oils from the silicone rubber mat. Halogenated solvents should
not be used on the silicone rubber mat material.
6.2 Remove any remaining oils from the silicone rubber mat. Do not use a soap-water solution.
6.2.1 Solvents should be avoided if possible when residue will be tested for performance properties.
6.2.2 VM&P naptha, heptane, or other mineral spirits may be used to remove the residual asphalt from the silicone rubber mat;
however, following the use of these materials wipe the silicone rubber mat with acetone or warm at 60 6 5 °C (140 6 10 °F) for
at least 15 min to remove residual solvent traces.
NOTE 2—VM&P naptha, heptane, or other mineral spirits are suggested to remove the residual asphalt from the silicone rubber mat. Following the use
of these materials wipe the silicone rubber mat with acetone or warm at 60 6 5°C (140 6 10°F) for at least 15 min. Alternative methods can be used
provided they are effective at removing residual asphalt and traces of solvents or mineral spirits from the silicone rubber mat.
7. Preparation of Apparatus
7.1 Pre-heatPreheat both the support material used during emulsified asphalt recovery and the vacuum oven or other suitable
pressure reduction vessel to 60 6 5°C5 °C (140 6 10°F)10 °F) for a minimum of 30 min.
NOTE 3—Preheating the vessel 10 to 15°C15 °C above the 60°C60 °C recovery temperature can be used to reduce the drop in chamber temperature during
loading and to minimize the time required to stabilize the system after loading to attain the required temperature range. The specific pre-heatpreheat
temperature offset used is equipment specific, so select the pre-heatpreheat temperature based on the value that minimizes the time delay between sample
loading and the system returning to the operating range provided in 7.1.
7.2 Wipe clean the material that will support the silicone rubber mat during draw down draw-down of the emulsified asphalt film
and inspect to ensure the surface is absent of any particles or other irregularities. It is not necessary to preheat the support material
used for draw down draw-down of the emulsified asphalt film.
8. Calibration and Standardization
8.1 Vacuum Oven:
8.1.1 Vacuum Oven Thermometric Device—Verify the thermometric device used in the vacuum oven to within 60 6 5°C5 °C (140
6 10°F)10 °F) at least every twelve months using a calibrated thermometric device traceable to a national standard. Verification
shall be performed at a temperature that is within 5°C5 °C of the use temperature.
8.1.2 Absolute Pressure Gauge—Verify the absolute pressure gauge to equate to a reading within 1300 6 500 Pa (0.4 6 0.2 inHg)
in. Hg) pressure at least every twelve months using a calibrated vacuum or pressure indicator traceable to a national standard.
NOTE 4—If a vacuum pressure gauge is used, the gauge reading represents the difference between atmospheric pressure and the pressure in the vessel.
This value must be converted to absolute pressure by adding the atmospheric pressure to the gauge pressure. Standard atmospheric pressure at sea level
is 101.3 kPa (29.92 inHg), correction for higher altitudes is required. A procedure for correcting gauge readings based on altitude is provided in Table
1 of AASHTO R28.
8.1.2.1 If a vacuum pressure gauge is used, the gauge reading represents the difference between atmospheric pressure and the
pressure in the vessel. This value must be converted to absolute pressure by adding the atmospheric pressure to the gauge pressure.
Standard atmospheric pressure at sea level is 101.3 kPa (29.92 in. Hg); correction for higher altitudes is required. A procedure for
correcting gauge readings based on altitude is provided in Table 1 of AASHTO R 28.
9. Conditioning
9.1 Handle emulsions in accordance with Test Methods D244 subsection 3.1 with the following modifications: Increase the sample
heating temperature to 55 6 5°C5 °C (131 6 10°F)10 °F) for all emulsions regardless of emulsion viscosity testing requirements.
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