1、Standard Method of Test for Determining the Asphalt Binder Content of Asphalt Mixtures by the Ignition Method AASHTO Designation: T 308-18 Technical Section: 2c, AsphaltAggregate Mixtures Release: Group 3 (August) American Association of State Highway and Transportation Officials 444 North Capitol S
2、treet N.W., Suite 249 Washington, D.C. 20001 TS-2c T 308-1 AASHTO Standard Method of Test for Determining the Asphalt Binder Content of Asphalt Mixtures by the Ignition Method AASHTO Designation: T 308-18 Technical Section: 2c, AsphaltAggregate Mixtures Release: Group 3 (August) 1. SCOPE 1.1. This t
3、est method covers the determination of asphalt binder content of asphalt mixtures by ignition at temperatures that reach the flashpoint of the binder in a furnace. The means of specimen heating may be the convection method or the direct infrared (IR) irradiation method. The aggregate remaining after
4、 burning can be used for sieve analysis using T 30. 1.2. The values stated in SI units are to be regarded as the standard. 1.3. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all of the safety concerns associated with its use. It i
5、s the responsibility of the user of this standard to consult and establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 231, Weighing Devices Used in the Testing of Materials R 47, Red
6、ucing Samples of Hot Mix Asphalt (HMA) to Testing Size R 66, Sampling Asphalt Materials R 76, Reducing Samples of Aggregate to Testing Size R 90, Sampling Aggregate Products T 30, Mechanical Analysis of Extracted Aggregate T 168, Sampling Bituminous Paving Mixtures T 329, Moisture Content of Asphalt
7、 Mixtures by Oven Method 2.2. ASTM Standard: C670, Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials 2.3. Other Documents: Manufacturers Instruction Manual NCHRP Final Report, NCHRP Project No. 9-26, Phase 3 2018 by the American Association of
8、State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c T 308-2 AASHTO 3. SUMMARY OF TEST METHOD 3.1. The asphalt binder in the asphalt mixture is ignited using the furnace equipment applicable to the particular method. This procedure cover
9、s two methods. Method A requires an ignition furnace with an internal balance. Method B requires an ignition furnace with an external balance. 3.2. The asphalt binder content is calculated as the difference between the initial mass of the asphalt mixture and the mass of the residual aggregate, with
10、adjustments for an asphalt binder correction factor and the moisture content. The asphalt binder content is expressed as a mass percent of the moisture-free mixture. This method may be affected by the type of aggregate in the mixture. Accordingly, to optimize accuracy, correction factors for asphalt
11、 binder and aggregate will be established by testing a set of correction factor specimens for each type of asphalt mixture. Correction factors must be determined before any acceptance testing is performed. 4. SIGNIFICANCE AND USE 4.1. This method can be used for quantitative determinations of asphal
12、t binder content and gradation in asphalt mixture and pavement specimens for quality control, specification acceptance, and mixture evaluation studies. This method does not require the use of solvents. Aggregate obtained by this test method may be used for gradation analysis according to T 30. 5. AP
13、PARATUS 5.1. Ignition FurnaceA forced-air ignition furnace that heats the specimens by either the convection or direct IR irradiation method. The convection-type furnace must be capable of maintaining a temperature of 538 5C (1000 9F). The furnace chamber dimensions shall be adequate to accommodate
14、a specimen size of 3500 g. The furnace door shall be equipped so that the door cannot be opened during the ignition test. A method for reducing furnace emissions shall be provided. The furnace shall be vented into a hood or to the outside and, when set up properly, shall have no noticeable odors esc
15、aping into the laboratory. The furnace shall have a fan capable of pulling air through the furnace to expedite the test and reduce the escape of smoke into the laboratory. 5.1.1. For Method A, the furnace shall also have an internal balance thermally isolated from the furnace chamber and accurate to
16、 0.1 g. The balance shall be capable of weighing a 3500-g specimen in addition to the specimen baskets. A data collection system will be included so that the mass can be automatically determined and displayed during the test. The furnace shall have a built-in computer program to calculate the change
17、 in mass of the specimen baskets and provide for the input of a correction factor for aggregate loss. The furnace shall provide a printed ticket with the initial specimen mass, specimen mass loss, temperature compensation, correction factor, corrected asphalt binder content (percent), test time, and
18、 test temperature. The furnace shall provide an audible alarm and indicator light when the specimen mass loss does not exceed 0.01 percent of the total specimen mass for 3 consecutive min. The furnace shall also allow the operator to change the ending mass loss percentage to 0.02 percent. 5.2. Speci
19、men Basket AssemblyConsisting of specimen basket(s), catch pan, and an assembly guard to secure the specimen basket(s) to the catch pan. 5.2.1. Specimen Basket(s)Of appropriate size to allow the specimens to be thinly spread and allow air to flow through and around the specimen particles. Sets with
20、two or more baskets shall be nested. The specimen shall be completely enclosed with screen mesh, perforated stainless steel plate, or other suitable material. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable
21、 law.TS-2c T 308-3 AASHTO Note 1Screen mesh or other suitable material with maximum and minimum openings of 2.36 mm (No. 8) and 0.600 mm (No. 30), respectively, has been found to perform well. 5.2.2. Catch PanOf sufficient size to hold the specimen basket(s) so that aggregate particles and melting a
22、sphalt binder falling through the screen are caught. 5.3. OvenCapable of maintaining 110 5C (230 9F). 5.4. BalanceOf sufficient capacity and conforming to the requirements of M 231, Class G 2. 5.5. Safety EquipmentSafety glasses or face shield, dust mask, high-temperature gloves, long-sleeved jacket
23、, a heat-resistant surface capable of withstanding 650C (1202F), and a protective cage capable of surrounding the specimen baskets during the cooling period. 5.6. Miscellaneous EquipmentA pan larger than the specimen basket(s) for transferring the specimen after ignition, spatulas, bowls, and wire b
24、rushes. 6. SAMPLING 6.1. Obtain samples of freshly produced asphalt mixture in accordance with T 168. 6.2. The specimen shall be the end result of reducing a larger sample in accordance with R 47. 6.3. If the mixture is not sufficiently soft to separate with a spatula or trowel, place it in a large,
25、 flat pan in an oven at 110 5C (230 9F) until it is workable. Do not leave the specimen in the oven for an extended period of time. Excessive heating may cause detrimental effects such as asphalt draindown or oxidation. 6.4. The size of the test specimen shall be governed by the nominal-maximum aggr
26、egate size of the asphalt mixture and shall conform to the mass requirement shown in Table 1. When the mass of the specimen exceeds the capacity of the equipment used, the specimen may be divided into suitable increments, tested, and the results appropriately combined for calculation of the asphalt
27、binder content (using a weighted average). Specimen sizes shall not be more than 500 g greater than the minimum recommended specimen mass. Note 2Large specimens of fine mixes tend to result in incomplete ignition of asphalt binder. Table 1Mass Requirements Nominal- Maximum Aggregate Size,amm Sieve S
28、ize Minimum Mass of Specimen, g 4.75 No. 4 1200 9.5 3/8in. 1200 12.5 1/2in. 1500 19.0 3/4in. 2000 25.0 1 in. 3000 37.5 11/2in. 4000 aNominal-maximum aggregate sizeone size larger than the first sieve to retain more than 10 percent. 2018 by the American Association of State Highway and Transportation
29、 Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c T 308-4 AASHTO TEST METHOD AINTERNAL BALANCE 7. TEST PROCEDURES 7.1. Test Initiation: 7.1.1. For the convection-type furnace, preheat the ignition furnace to 538 5C (1000 9F) or to the temperature determined by the c
30、orrection factor process in the Annex. Manually record the furnace temperature (set point) prior to the initiation of the test if the furnace does not record automatically. 7.1.2. For the direct IR irradiation-type furnace, use the same burn profile as used during the correction factor determination
31、. 7.2. Oven dry the asphalt mixture specimen to a constant mass at a temperature of 110 5C (230 9F), or determine the moisture content of a companion specimen according to T 329. 7.3. Enter into the ignition furnace, or manually record, the asphalt binder correction factor for the specific mix to be
32、 tested, as determined in the Annex. 7.4. Determine and record the mass of the specimen basket assembly to the nearest 0.1 g. 7.5. Prepare the specimen as described in Section 6. Place the specimen basket(s) in the catch pan. Evenly distribute the specimen in the basket(s), taking care to keep the m
33、aterial away from the edges of the basket. Use a spatula or trowel to level the specimen. 7.6. Determine and record the total mass of the specimen and specimen basket assembly at room temperature to the nearest 0.1 g. Calculate and record the initial mass of the specimen, Mi(total mass minus the mas
34、s of the specimen basket assembly). 7.7. Input the initial mass of the specimen, Mi, in whole grams into the ignition furnace controller. Verify that the correct mass has been entered. 7.8. Open the chamber door and place the specimen basket assembly in the furnace, carefully positioning the specime
35、n basket assembly so it is not in contact with the furnace walls. Close the chamber door and verify that the specimen mass (including the basket assembly) displayed on the furnace scale equals the total mass recorded in Section 7.6 within 5 g. Differences greater than 5 g or failure of the furnace s
36、cale to stabilize may indicate that the specimen basket assembly is contacting the furnace wall. Note 3Due to the extreme heat of the furnace, the operator should wear safety equipmenthigh-temperature gloves, face shield, and fire-retardant shop coatwhen opening the door to load or unload the specim
37、en. 7.9. Initiate the test by pressing the start/stop button. This operation will lock the specimen chamber and start the combustion blower. Note 4The furnace temperature will drop below the set point when the door is opened but will recover with the door closed and when ignition occurs. Specimen ig
38、nition typically increases the temperature well above the set point, depending on the specimen size and asphalt binder content. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c T 308-5 AASHTO 7.10.
39、 Allow the test to continue until the stable light and audible stable indicator indicate the test is complete (the change in mass does not exceed 0.01 percent for 3 consecutive min). Press the start/stop button. This operation will unlock the specimen chamber and cause the printer to print out the t
40、est results. Note 5An ending mass loss percentage of 0.02 may be substituted when the aggregate exhibits an excessive amount of loss during ignition testing. The precision and bias statement was developed using 0.01 percent. Both precision and accuracy may be adversely affected by using 0.02 percent
41、. 7.11. Open the chamber door, remove the specimen basket assembly, and place it on a cooling plate or block. Place the protective cage over the specimen basket assembly, and allow it to cool to room temperature (approximately 30 min). 7.12. Determine and record the total mass of the specimen and sp
42、ecimen basket assembly after ignition to the nearest 0.1 g. Calculate and record the final mass of the specimen, Mf(total mass minus the mass of the specimen basket assembly). 7.13. Use the corrected asphalt binder content (percent) from the printed ticket. If this value is not corrected, subtract t
43、he asphalt binder correction factor. If a moisture content has been determined per T 329, subtract the percent moisture from the asphalt binder content on the printed ticket, and report the resultant value as the corrected asphalt binder content (Pb). Note 6Asphalt binder content can also be calcula
44、ted using Equation 1 from Method B (Section 8.16). TEST METHOD BEXTERNAL BALANCE 8. TEST PROCEDURES 8.1. Preheat the ignition furnace to 538 5C (1000 9F) or the temperature determined by the correction factor process in the Annex. 8.2. Oven dry the asphalt mixture specimen to a constant mass at a te
45、mperature of 110 5C (230 9F), or determine the moisture content of a companion specimen according to T 329. 8.3. Record the asphalt binder correction factor for the specific mix to be tested, as determined by the correction factor process in the Annex. 8.4. Determine and record the mass of the speci
46、men basket assembly to the nearest 0.1 g. 8.5. Prepare the specimen as described in Section 6. Place the specimen baskets in the catch pan. Evenly distribute the specimen in the basket(s), taking care to keep the material away from the edges of the basket. Use a spatula or trowel to level the specim
47、en. 8.6. Determine and record the total mass of the specimen basket assembly at room temperature to the nearest 0.1 g. Calculate and record the initial mass of the specimen, Mi(total mass minus the mass of the specimen basket assembly). 8.7. Open the chamber door and place the specimen basket assemb
48、ly in the furnace. Burn the asphalt mixture specimen in the furnace for at least 45 min. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c T 308-6 AASHTO Note 7The appropriate time for the initial b
49、urn of an asphalt mixture specimen is dependent on the specimen size. For large specimens, the time could be significantly longer than 45 min. See the Manufacturers Instruction Manual for guidelines. 8.8. Open the chamber door, remove the specimen basket assembly, and place it on a cooling plate or block. Place the protective cage over the specimen basket assembly, and allow it to cool to room temperature (approximately 30 min). 8.9. Determine and record the total mass of the specimen and s
