1、Standard Method of Test for Quantitative Determination of the Percentage of Lime in Hot Mix Asphalt (HMA) AASHTO Designation: TP 72-08 (2013)1American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2c TP 72-1 AASHTO Standa
2、rd Method of Test for Quantitative Determination of the Percentage of Lime in Hot Mix Asphalt (HMA) AASHTO Designation: TP 72-08 (2013)11. SCOPE 1.1. This method covers the quantitative determination of the percentage of lime in hot mix asphalt (HMA) by calculation of the calcium hydroxide, Ca(OH)2,
3、 recovered from a sample of the mixture. A specimen is obtained through drilling into the HMA and collecting the drilling dust. The specimen is subjected to an acid filter boil and wash and is analyzed using either Atomic Absorption (AA) or Ion Exchange Chromatography (IEC). 1.2. This standard may i
4、nvolve hazardous materials, operations, and equipment. 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 and health practices and determine the applicability of
5、regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 231, Weighing Devices Used in the Testing of Materials T 308, Determining the Asphalt Binder Content of Hot Mix Asphalt (HMA) by the Ignition Method 2.2. ASTM Standard: C 25, Standard Test Methods for Chemical Anal
6、ysis of Limestone, Quicklime, and Hydrated Lime 3. SIGNIFICANCE AND USE 3.1. This test method is useful for determining the amount of lime added to an HMA mixture. 3.2. If the coarse aggregate contains limestone, the limestone aggregate will be dissolved by the acid used in this method and can yield
7、 an unrealistically high result. If limestone is present in a relatively minor amount, it is possible to run a background analysis on the raw aggregate. An adjustment can then be made based on the background analysis in order to better approximate the actual results. If the aggregate in the HMA cont
8、ains an appreciable amount of limestone, this test method is not suitable. Depending upon the concentration, the calcium content of any added lime could be masked by the aggregate concentration. This effect would lead to a significant error in overestimation of the amount of lime added. 2014 by the
9、American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c TP 72-2 AASHTO 4. APPARATUS 4.1. Atomic Absorption (AA) or Ion Exchange Chromatography (IEC)These methods are able to measure the concentration of chemical eleme
10、nts, in this case calcium, in aqueous solutions. AA Spectrometry measures the intensity of a characteristic color imparted to a flame by the presence of calcium ions in the test solution. IEC measures the change in electrical conductivity of the solution. IEC can identify components of mixtures; AA
11、Spectrometry can only measure one element at a time. 4.2. BalanceAn analytical balance conforming to M 231, Class B. 4.3. Heating DeviceA small hot plate or other suitable device shall be available for supplying sufficient heat under the flask to bring the solution to a boil. Suitable shields, baffl
12、e plates, or sand baths shall be used on the surfaces of the hot plates to minimize localized overheating. 4.4. Rotary HammerAn industrial size hammer drill with a 3/8-in. carbide drill bit. 4.5. Miscellaneous Equipment: 4.5.1. Automatic PipetteEppendorf or equivalent of adequate capacity to obtain
13、a 1.0-mL sample. 4.5.2. Filter FunnelBuchner or equivalent and filter paper, filter flask, and a vacuum source. 4.5.3. Glassware100- and 250-mL flasks. 5. TEST SPECIMENS 5.1. Test specimens may be either laboratory-mixed HMA or sampled from HMA pavements. 5.2. Pavement specimens shall be taken from
14、pavements with a core drill, diamond or carborundum saw, or by other suitable means. Specimens will be further prepared as noted in Section 6.1. 5.3. Specimens shall be free from foreign materials such as foundation material, soil, paper, foil, etc. 5.4. If the core contains more than one pavement l
15、ayer, it is recommended that the layers be separated by sawing or other suitable means. 6. PROCEDURE 6.1. Preparation of Specimen: 6.1.1. A specimen is obtained from the drilling dust of a pavement core or laboratory-mixed HMA sample. Stand the core on a thick piece of wood and use a heavy-duty rota
16、ry hammer with a 3/8-in. carbide bit to drill into the sample. Note 1A rotary hammer that utilizes SDS, SDS Max, or spline shank bits is recommended. Devices utilizing straight shank bits have been found to be insufficient. Depending upon the number of samples, it may be worthwhile to make a frame t
17、o hold the core. Note 2It is recommended to wear safety glasses and protective gloves. 6.1.2. Drill to the depth of the drill flutes. This depth will yield about 15 g of dust. Discard any lumps of the core that may break off. 2014 by the American Association of State Highway and Transportation Offic
18、ials.All rights reserved. Duplication is a violation of applicable law.TS-2c TP 72-3 AASHTO 6.1.3. Take the 15 0.5 g of dust and determine its mass to the nearest 0.01 g. Place the dust in a 250-mL conical flask. Add 100 mL of 4 percent acetic acid and boil the mixture for 30 to 45 min. Filter the m
19、ixture through a filter funnel (Buchner or equivalent) and wash the insoluble dust with distilled water. 6.1.4. Transfer the filtrate to a 250-mL volumetric flask. Rinse the filter flask with distilled water and add the washings to the contents of the volumetric flask. Add distilled water to the fla
20、sk until the total volume of its contents reaches 250 mL. Place a stopper in the flask, and shake it well to mix the contents. 6.1.5. Use a pipette (an Eppendorf automatic pipette or equivalent) accurate to 0.1 mL to take a 1.0-mL aliquot from the volumetric flask, and transfer this specimen to a 10
21、0-mL volumetric flask. Fill the flask with distilled water until the total volume of its contents reaches 100 mL. Place a stopper in the flask, and shake it well to mix the contents. 6.2. Analyze the drilling dust to determine the level of calcium ions present: 6.2.1. Run AA Spectrometry or IEC (acc
22、ording to the manufacturers recommendations) on the specimen prepared in Section 6.1.5. Run calcium standards before and after the specimen analysis. If using AA Spectrometry, do not add lanthanum salts. Note 3Theories exist that calcium is subject to interference with AA Spectrometry and this condi
23、tion can be overcome by adding lanthanum salts. However, in this procedure, it has been found to provide an artificially high lime result. 6.2.2. The calcium ion concentration in the specimen should be in the range of 1 to 5 mg/L. If the concentration is outside this range, it indicates the possible
24、 presence of limestone aggregate (see Section 3.2). 7. CALCULATION OF RESULTS 7.1. Calculate the percentage of lime in the HMA as follows: L = C 46.25/10 Wd (100 AC)/100)/Lc(1) where: L = percentage of lime; C = concentration of calcium from AA or IEC (mg/L); Wd= mass of the dust, g; AC = percentage
25、 of the binder in the mix, determined by T 308; and Lc= percentage of calcium in the lime from ASTM C 25 to the nearest 0.001 (e.g., 0.955). 7.1.1. Derivation of Equation 1: The calcium content of the original solution is: C 100/4 mg/L or C 25. Hydrated lime is calcium hydroxide Ca(OH)2with a molecu
26、lar weight of 40 + 2(16 + 1) = 74. To convert from mg/L of calcium to mg/L of lime multiply by 74/40 or 1.85. Therefore, the hydrated lime content is: C 25 1.85 mg/L or C 46.25 mg/L Hydrated lime is added to the mix as a percentage of the aggregate; therefore, the mass of the aggregate in the dust s
27、pecimen is included as 1000 Wd (100 AC)/100 in grams or 10 Wd (100 AC)/100 in milligrams. 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c TP 72-4 AASHTO 8. REPORT 8.1. The report shall include the
28、following information: 8.1.1. Type of specimen tested (obtained from a laboratory-mixed sample or pavement core sample); Note 4For core specimens, the height of each test specimen in millimeters (or inches) should be reported. 8.1.2. Date of the test; 8.1.3. Asphalt mixture identification; 8.1.4. Pe
29、rcentage of asphalt binder to the nearest 0.1 percent; and 8.1.5. Percentage of lime to the nearest 0.01 percent. 9. PRECISION AND BIAS 9.1. No precision and bias statements are available at this time. 10. KEYWORDS 10.1. Atomic Absorption Spectrometry; hot mix asphalt; Ion Exchange Chromatography; lime. 1This provisional standard was first published in 2008. 2014 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
