National Academies Press: OpenBook

Investigation of Short-Term Laboratory Aging of Neat and Modified Asphalt Binders (2011)

Chapter: Appendix F - Draft AASHTO Standard for the MGRF

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Page 67
Suggested Citation:"Appendix F - Draft AASHTO Standard for the MGRF." National Academies of Sciences, Engineering, and Medicine. 2011. Investigation of Short-Term Laboratory Aging of Neat and Modified Asphalt Binders. Washington, DC: The National Academies Press. doi: 10.17226/14613.
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Page 67
Page 68
Suggested Citation:"Appendix F - Draft AASHTO Standard for the MGRF." National Academies of Sciences, Engineering, and Medicine. 2011. Investigation of Short-Term Laboratory Aging of Neat and Modified Asphalt Binders. Washington, DC: The National Academies Press. doi: 10.17226/14613.
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Page 68

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Standard Method of Test for Modified German Rotating Flask Equivalent of Rolling Thin Film Oven Test for Conventional Asphalts 1. Scope 1.1 This standard serves to simulate the changes in rheolog- ical properties in a conventional asphalt sample due to exposure to heat and a simultaneous supply of air. It is a large-scale version of the Rolling Thin Film Oven Test (AASHTO T-240). 1.2 This method is applicable to conventional asphalts. 1.3 This standard may involve hazardous materials, opera- tions and equipment. This standard does not purport to address all of the safety problems associated with its use. It is the responsibility of the user of this standard to estab- lish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. Reference Documents 2.1 AASHTO and DIN Standards T-240, Effects of Heat and Air on a Moving Thin Film of Asphalt [Rolling Thin Film Oven Test]. T-179, Effects of Heat and Air on Asphalt Materials [Thin Film Oven Test]. DIN 52016, Testing the Thermal Stability of Bitumen in a Rotating Flask. 3. Summary 3.1 A 200-gram conventional asphalt sample is placed in a Morton flask attached to a rotary evaporator with a spring clip for 210 minutes at 165°C, with 2,000 mL/min air being supplied continuously. The flask is continu- ously rotated at 20 rpms to prevent a hard skin forming on the asphalt sample’s surface. 3.2 The mass loss is determined and the conventional asphalt sample is then tested to determine the effects of heat and air. 4. Apparatus The following apparatus shall be used: (a) Rotary evaporator (without condenser and receiver) fitted with an adapter for a 45/50 – $ joint, capable of being adjusted to a speed of (20 ± 5) rpm; (b) 2,000 mL Morton flask with a 45/50 – $ joint; (c) Glass air supply tube, minimum of 550 mm long with an inside diameter of 7 mm, to be inserted into the flask; (d) Compressor equipped with filter and air drier or bot- tled compressed air of industrial or breathing grade quality; (e) Gas flow control device, capable of adjusting the flow rate to 2,000 ± 40 mL/min corrected to standard baro- metric pressure; (f) Gas flow meter with a limit of error of ± 40 mL/min at a flow rate of 2,000 mL/min; (g) Thermostatically controlled bath capable of being maintained at a temperature of 165 ± 1.5°C while immersing a 2,000 mL Morton flask to a depth where the sample, while rotating, is below the level of the bath fluid (see Figure 1); (h) Bath wax heat transfer liquid with a flash point of greater than 300°C, capable of being safely maintained at operating temperatures; (i) ASTM Loss on Heat Thermometer 13C, immersed in the bath up to the 163°C mark in a vertical position; (j) Balance with a capacity of 1,000 grams and accurate to 0.01 g; (k) Oven capable of being adjusted to 165 ± 1.5°C. A P P E N D I X F Draft AASHTO Standard for the MGRF 67

68 5. Procedure 5.1 Exposure of Asphalt to Heat Including Determination of Change in Mass Weigh 200 ± 1 g of the sample (i.e., the specimen) into the tared flask and, after the specimen has cooled to ambient temperature (18 to 28°C), determine the initial mass (me) and report it to the nearest 0.01 g. Place the Morton flask containing the specimen in the bath, with its axis at 45° to the horizontal and its bulbous part immersed so that the sample, while rotating, is below the level of the bath fluid maintained at a temperature of 165 ± 1.5°C (see Figure 1). The 13C thermometer should be immersed in the bath up to the 163°C mark in a vertical position. Use cau- tion during this step to avoid splashing of the hot bath wax. Fix the air supply tube so that its axis coincides with that of the flask, with a clearance of 50 ± 2 mm between tube and flask bottom. Heat the specimen for 10 ± 1 minutes while rotating the flask at 20 ± 5 rpm. Then, introduce air at ambient tempera- ture, at a rate of 2,000 ± 40 mL/min. During the test, main- tain the bath temperature at 165 ± 1.5°C and rotate the flask at 20 ± 5 rpm. After 210 ± 1 minutes, measured from the time when flask was first immersed, stop both the air flow and the flask rota- tion, and immediately remove the flask from the bath. When the flask has cooled slightly, carefully remove all bath wax residue adhering to its surface for proper mass determina- tion. Caution: The surface may still be hot. Cool the flask to ambient temperature (18 to 28°C), deter- mine the final mass of the flask (ma) and report it to the near- est 0.01g. Heat the contents of the flask in an inverted position with an 8-oz ointment tin placed under the mouth of the flask in an oven at 160 ± 5°C for approximately 15 to 20 minutes, or until the sample has stopped dripping out of the flask. Fol- lowing that, transfer the specimen to the vessels or molds required for subsequent testing. 5.2 Exposure of Bitumen to Heat without Determining the Change in Mass (TB) Proceed as specified in Subclause 5.1 using a bitumen spec- imen of 200 ± 1 g, determination of the initial mass (me) to an accuracy of 0.01 g not being required here. Following exposure to heat, carefully remove all bath wax residue adhering to its surface. Caution: The surface may still be hot. Place the flask in an inverted position with an 8-oz. ointment tin placed under the mouth of the flask in an oven at 160 ± 5°C for approximately 15 to 20 minutes, or until the sample has stopped dripping out of the flask. Following that, transfer the specimen to the vessels or molds required for subsequent testing. 6. Evaluation and Expression of Results The change in mass, Δm, shall be calculated as a percentage by mass, expressed to the nearest 0.01%, using the following equation: where: me is the specimen mass prior to heat exposure; ma is the specimen mass after heat exposure. 7. Precision and Bias Precision—The research required to develop precision estimates for this test method has not been conducted. Bias—The research required to develop precision estimates for this test method has not been conducted. Δm m m m % = − ×a e e 100 Figure 1. Test arrangement.

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Investigation of Short-Term Laboratory Aging of Neat and Modified Asphalt Binders Get This Book
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TRB’s National Cooperative Highway Research Program (NCHRP) Report 709: Investigation of Short-Term Laboratory Aging of Neat and Modified Asphalt Binders provides a proposed method of testing for short-term laboratory aging of neat and modified asphalt binders using the modified German rotating flask as an alternative to the rolling thin film oven test.

The following appendixes A-E to NCHRP Report 709 are only available in electronic format:

Appendix A: Binder Aging Bibliography

Appendix B: Selection Study Report

Appendix C: Volatile Collection System Study Report

Appendix D: SAFT Optimization Study Report

Appendix E: Verification Study Report

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