1、Standard Method of Test for Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method AASHTO Designation: T 308-16 Release: Group 3 (August 2016) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C.
2、20001 TS-2c T 308-1 AASHTO Standard Method of Test for Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method AASHTO Designation: T 308-16 Release: Group 3 (August 2016) 1. SCOPE 1.1. This test method covers the determination of asphalt binder content of hot mix aspha
3、lt (HMA) 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 burning can be used for sieve analysis using T 30. 1.2. The values state
4、d 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 is the responsibility of the user of this standard to consult and establis
5、h 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, Reducing Samples of Hot Mix Asphalt (HMA) to Testing Size R 66, Sampling Asp
6、halt Materials R 76, Reducing Samples of Aggregate to Testing Size T 2, Sampling of Aggregates T 30, Mechanical Analysis of Extracted Aggregate T 168, Sampling Bituminous Paving Mixtures T 329, Moisture Content of Asphalt Mixtures by Oven Method 2.2. ASTM Standard: C670, Standard Practice for Prepar
7、ing 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 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is
8、a violation of applicable law.TS-2c T 308-2 AASHTO 3. SUMMARY OF TEST METHOD 3.1. The asphalt binder in the HMA is ignited using the furnace equipment applicable to the particular method. This procedure covers two methods. Method A requires an ignition furnace with an internal balance. Method B requ
9、ires an ignition furnace with an external balance. 3.2. The asphalt binder content is calculated as the difference between the initial mass of the HMA and the mass of the residual aggregate, with adjustments for an asphalt binder correction factor and the moisture content. The asphalt binder content
10、 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 binder and aggregate will be established by testing a set of correction factor specimens for each type
11、of HMA. 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 asphalt binder content and gradation in HMA and pavement specimens for quality control, specification acceptance, and mixt
12、ure 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. APPARATUS 5.1. Ignition FurnaceA forced-air ignition furnace that heats the specimens by either the convection or direct IR irradi
13、ation 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 a specimen size of 3500 g. The furnace door shall be equipped so that the door cannot be opened during the ignition test. A meth
14、od 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 escaping into the laboratory. The furnace shall have a fan capable of pulling air through the furnace to expedite the test and redu
15、ce 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 0.1 g. The balance shall be capable of weighing a 3500-g specimen in addition to the specimen baskets. A data collection system
16、 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 in mass of the specimen baskets and provide for the input of a correction factor for aggregate loss. The furnace shall provide
17、a printed ticket with the initial specimen mass, specimen mass loss, temperature compensation, correction factor, corrected asphalt binder content (percent), test time, and test temperature. The furnace shall provide an audible alarm and indicator light when the specimen mass loss does not exceed 0.
18、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. Specimen Basket AssemblyConsisting of specimen basket(s), catch pan, and an assembly guard to secure the specimen basket(s) to the ca
19、tch 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 two or more baskets shall be nested. The specimen shall be completely enclosed with screen mesh, perforated stainless steel plat
20、e, or other suitable material. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable 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
21、.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 asphalt binder falling through the screen are caught. 5.3. OvenCapable of maintaining 110 5C (230 9F). 5.4. BalanceOf sufficient c
22、apacity 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, a heat-resistant surface capable of withstanding 650C (1202F), and a protective cage capable of surrounding the specimen basket
23、s 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 brushes. 6. SAMPLING 6.1. Obtain samples of freshly produced HMA in accordance with T 168. 6.2. The specimen shall be the end resu
24、lt 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, 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
25、 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 aggregate size of the HMA and shall conform to the mass requirement shown in Table 1. When the mass of the specimen exceeds the capacity of the e
26、quipment used, the specimen may be divided into suitable increments, tested, and the results appropriately combined for calculation of the asphalt binder content (using a weighted average). Specimen sizes shall not be more than 500 g greater than the minimum recommended specimen mass. Note 2Large sp
27、ecimens of fine mixes tend to result in incomplete ignition of asphalt binder. Table 1Mass Requirements Nominal- Maximum Aggregate Size,amm Sieve Size 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 aggr
28、egate sizeone size larger than the first sieve to retain more than 10 percent. 2016 by the American Association of State Highway and Transportation 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. T
29、est 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 correction factor process in the Annex. Manually record the furnace temperature (set point) prior to the initiation of the test if the furnace does not rec
30、ord automatically. 7.1.2. For the direct IR irradiation-type furnace, use the same burn profile as used during the correction factor determination. 7.2. Oven dry the HMA specimen to a constant mass at a temperature of 110 5C (230 9F), or determine the moisture content of a companion specimen accordi
31、ng to T 329. 7.3. Enter into the ignition furnace, or manually record, the asphalt binder correction factor for the specific mix to be 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 i
32、n Section 6. Place the specimen basket(s) 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 specimen. 7.6. Determine and record the total mass of the specimen and specimen basket
33、 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). 7.7. Input the initial mass of the specimen, Mi, in whole grams into the ignition furnace controller. Verify that the correct mass
34、 has been entered. 7.8. Open the chamber door and place the specimen basket assembly in the furnace, carefully positioning the specimen 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 o
35、n 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 scale 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 wea
36、r safety equipmenthigh-temperature gloves, face shield, and fire-retardant shop coatwhen opening the door to load or unload the specimen. 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 tempera
37、ture will drop below the set point when the door is opened but will recover with the door closed and when ignition occurs. Specimen ignition typically increases the temperature well above the set point, depending on the specimen size and asphalt binder content. 2016 by the American Association of St
38、ate Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c T 308-5 AASHTO 7.10. 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 co
39、nsecutive min). Press the start/stop button. This operation will unlock the specimen chamber and cause the printer to print out the test 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 preci
40、sion and bias statement was developed using 0.01 percent. Both precision and accuracy may be adversely affected by using 0.02 percent. 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 assemb
41、ly, and allow it to cool to room temperature (approximately 30 min). 7.12. Determine and record the total mass of the specimen and specimen 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 as
42、sembly). 7.13. Use the corrected asphalt binder content (percent) from the printed ticket. If this value is not corrected, subtract the 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
43、ticket, and report the resultant value as the corrected asphalt binder content (Pb). Note 6Asphalt binder content can also be calculated 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 temper
44、ature determined by the correction factor process in the Annex. 8.2. Oven dry the HMA 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. 8.3. Record the asphalt binder correction factor for the specific mix t
45、o be tested, as determined by the correction factor process in the Annex. 8.4. Determine and record the mass of the specimen 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 b
46、asket(s), taking care to keep the material away from the edges of the basket. Use a spatula or trowel to level the specimen. 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(to
47、tal mass minus the mass of the specimen basket assembly). 8.7. Open the chamber door and place the specimen basket assembly in the furnace. Burn the HMA specimen in the furnace for at least 45 min. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Du
48、plication is a violation of applicable law.TS-2c T 308-6 AASHTO Note 7The appropriate time for the initial burn of an HMA 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.
49、 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 specimen basket assembly after cooling to the nearest 0.1 g. 8.10. Place the specimen and specimen basket assembly back into the furnace. 8.11. Burn the specimen for at least 15 min after the furnace reaches
