Click for next page ( 68


The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

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

OCR for page 67
68 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 28C), 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 5C 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 Figure 1. Test arrangement. 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 5. Procedure an accuracy of 0.01 g not being required here. 5.1 Exposure of Asphalt to Heat Including Following exposure to heat, carefully remove all bath wax Determination of Change in Mass residue adhering to its surface. Caution: The surface may still be hot. Place the flask in an inverted position with an 8-oz. Weigh 200 1 g of the sample (i.e., the specimen) into the ointment tin placed under the mouth of the flask in an oven tared flask and, after the specimen has cooled to ambient at 160 5C for approximately 15 to 20 minutes, or until the temperature (18 to 28C), determine the initial mass (me) and sample has stopped dripping out of the flask. Following that, report it to the nearest 0.01 g. transfer the specimen to the vessels or molds required for Place the Morton flask containing the specimen in the subsequent testing. bath, with its axis at 45 to the horizontal and its bulbous part immersed so that the sample, while rotating, is below the level 6. Evaluation and Expression of the bath fluid maintained at a temperature of 165 1.5C of Results (see Figure 1). The 13C thermometer should be immersed in The change in mass, m, shall be calculated as a percentage the bath up to the 163C mark in a vertical position. Use cau- by mass, expressed to the nearest 0.01%, using the following tion during this step to avoid splashing of the hot bath wax. equation: 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 ma - me m% = 100 flask bottom. me Heat the specimen for 10 1 minutes while rotating the where: flask at 20 5 rpm. Then, introduce air at ambient tempera- me is the specimen mass prior to heat exposure; ture, at a rate of 2,000 40 mL/min. During the test, main- ma is the specimen mass after heat exposure. tain the bath temperature at 165 1.5C and rotate the flask at 20 5 rpm. 7. Precision and Bias After 210 1 minutes, measured from the time when flask Precision--The research required to develop precision was first immersed, stop both the air flow and the flask rota- estimates for this test method has not been conducted. tion, and immediately remove the flask from the bath. When Bias--The research required to develop precision estimates the flask has cooled slightly, carefully remove all bath wax for this test method has not been conducted.