1、Standard Method of Test for Evaluation of Oxidation Level of Asphalt Mixtures by a Portable Infrared Spectrometer AASHTO Designation: TP 128-171Technical Section: 2c, AsphaltAggregate Mixtures Release: Group 3 (August 2017) American Association of State Highway and Transportation Officials 444 North
2、 Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2c TP 128-1 AASHTO Standard Method of Test for Evaluation of Oxidation Level of Asphalt Mixtures by a Portable Infrared Spectrometer AASHTO Designation: TP 128-171Technical Section: 2c, AsphaltAggregate Mixtures Release: Group 3 (August 2017)
3、 1. SCOPE 1.1. This method covers the measurement of the oxidation signal in an asphalt mixture by a portable infrared spectrometer (PIRS) equipped with a diffuse reflectance accessory. Three oxidation signals are compared: (1) the in-place pavement, (2) asphalt mixture production sample, and (3) th
4、e approved job mixture formula specimen. The oxidation signals are determined from a specified peak value from the absorbance spectrum of the asphalt samples. 1.2. The in-place pavement PIRS oxidation signal can be used to assess its aging rate. The pavement aging rate is determined by comparing its
5、 initial PIRS oxidation signal with successive PIRS oxidation signals obtained at some defined frequency. 1.3. This standard does not purport to address all the safety concerns associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health p
6、ractices and determine the applicability of regulatory limitations prior to use. See Section 12 for more details. 2. REFERENCED DOCUMENT 2.1. AASHTO Standard: T 168, Sampling Bituminous Paving Mixtures 3. TERMINOLOGY 3.1. Definitions: 3.1.1. asphalt aging ratethe change of asphalt chemical propertie
7、s with time. 3.1.2. diffuse reflectance Fourier transform infrared spectroscopy (DRIFTS)an infrared technique used on rough surfaces where the infrared light is reflected and transmitted at different amounts depending on the bulk properties of the material. 3.1.3. Fourier transform infrared (FTIR) s
8、pectrometerthe most common type of spectrometer. 3.1.4. infrared spectrometeran instrument used to obtain infrared spectra. TS-2c TP 128-2 AASHTO 3.1.5. infrared spectroscopythe study of the interaction of infrared light with matter. 3.1.6. infrared spectruma plot of the measured infrared intensity
9、versus wavelength. 3.1.7. oxidation signalthe infrared absorbance value at some specified wavenumber. 4. SIGNIFICANCE AND USE 4.1. The test method described is useful as a rapid, nondestructive technique to monitor and detect differences in the oxidation signal of the preproduction laboratory asphal
10、t mixture, its production at the plant, and the newly placed pavement. 4.2. The oxidation values obtained from an asphalt pavement by this test method can be used to determine its aging rate by measuring the pavement oxidation values every six months or at another suitable frequency. Over time, the
11、oxidation values will increase and a pavement aging rate can be obtained. 4.3. The test method is useful to measure the oxidation values for monitoring the consistency of asphalt mixtures containing reclaimed asphalt pavement (RAP). 5. APPARATUS 5.1. Portable Fourier Transform Infrared (FTIR) Spectr
12、ometer Equipped with a Diffuse Reflection Accessory: 5.1.1. The spectrometer should be equipped with a portable battery to ensure a reliable power supply during testing. 5.2. Sampling Equipment: 5.2.1. Suitable metal scoop and containers to obtain asphalt mixture samples as described by T 168. 5.2.2
13、. Sampling stainless steel pipes for filling and compacting the asphalt mixture samples. Suitable dimensions are a minimum diameter of 25 mm (1 in.) and a height of 51mm (2 in.). 5.2.3. Optional sampling cylinder and metal tube used to compact and prepare a smooth surface on the specimen. 5.2.4. Ord
14、inary hammer to compact the asphalt mixture specimen in the stainless steel pipe to obtain a flat surface. 5.2.5. Standard sieves No. 4 (4.75 mm), No. 8 (2.36 mm), and No. 30 (0.6 mm) for sieving the test specimen material from a sample of the loose asphalt mixture. 5.2.6. Soft cloth or tissue for c
15、leaning the PIRS device. 6. SPECIMEN SAMPLING, FABRICATION, AND TESTING PROCEDURE 6.1. Preparation of Plant-Produced Asphalt Mixture Samples: 6.1.1. Collect a representative sample of plant-produced asphalt mixture according to T 168. 2017 by the American Association of State Highway and Transportat
16、ion Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c TP 128-3 AASHTO 6.1.2. Fill the stainless steel pipe with the warm asphalt mixture. Use a hammer with the metal tube to compact it until a flat surface is obtained as shown in Figure 1. Figure 1Steel Sampling Pipe
17、 with Compacted Plant Mixture: Side and Top Views 6.1.3. After the sample prepared in Section 6.1.2 cools down to a temperature of 60C (140F) or less, test the surface of the sample with the PIRS device. Make sure the sample is in full contact with the PIRS device as described in Section 7. 6.1.4. T
18、est five specimens using the procedures in Sections 6.1.1 through 6.1.3, with three repetitions each. 6.2. Preparation of Laboratory Asphalt Mixture Specimens: 6.2.1. Use the metal scoop from Section 5.2.1 to obtain a sample of asphalt mixture. Sieve the asphalt mixture sample and collect the materi
19、al passing the No. 8 (2.36-mm) sieve and retained on the No. 30 (0.6-mm) sieve (Figure 2). Figure 2Tools for Preparing a Sample from Laboratory Material 6.2.2. Collect the retained asphalt mixture with the metal scoop and fill the sampling cylinder. 6.2.3. Use a hammer with the metal tube to compact
20、 the asphalt mixture to the top level of the sampling cylinder; ensure a flat surface on the sample (Figure 1) and test the sample with the PIRS device, making sure they are in contact as described in Section 7. 6.2.4. Test five specimens using the procedures in Sections 6.2.1 through 6.2.3, with th
21、ree repetitions each. Asphalt mix sample passingNo. 8 retained on No. 30Sampling cylinder filledwith materialMetal tube to compact mixture 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c TP 128-4
22、AASHTO 6.3. Preparation of Reclaimed Asphalt Pavement (RAP) Samples: 6.3.1. If testing the oxidation of reclaimed asphalt pavement (RAP), sample the RAP from stockpiled material in accordance with T 168. 6.3.2. Obtain a sample of approximately 22 kg (10 lb) of RAP material from the designated RAP st
23、ockpile. 6.3.3. Sieve the RAP sample through No. 4 (4.75-mm), No. 8 (2.36-mm), and No. 30 (0.6-mm) sieves. 6.3.4. Use the material retained on the No. 30 (0.6-mm) sieve to fill the stainless steel pipe (Figure 2). 6.3.5. Use a hammer with the metal tube to compact the sample to the top level of the
24、stainless steel pipe to obtain a flat surface (Figure 1), and then test with the PIRS device, making sure they are in contact as described in Section 7. 6.3.6. Test five specimens using the procedures in Sections 6.3.2 through 6.3.5, with three repetitions each. Note 1Section 6.3 is skipped if the a
25、sphalt mixture does not contain RAP. 6.4. In-Place Pavement Surface Measurement: 6.4.1. Randomly select a relatively flat and dry pavement surface area. Brush the surface clear of any material that would prevent contact between the surface and the PIRS device. 6.4.2. The selected pavement area shoul
26、d be marked; take care not to place the PIRS device directly on the marking. 6.4.3. Perform three measurements on the selected pavement area with the PIRS device, as described in Section 7, and away from the wheel path. 6.4.4. Repeat the steps indicated in Sections 6.4.1 through 6.4.3 to test five p
27、avement areas with three repetitions each using the PIRS device. 6.4.5. If an agency sampling plan requires more samples, follow the agency sampling plan. Note 2A sampling plan may follow the process used to generate random numbers that determine which five sections of the pavement are to be measure
28、d, similar to that used to determine where density is measured on compacted pavement. Alternatively, a sampling plan may be defined by the agency. 7. SPECTROSCOPIC EQUIPMENT SETUP 7.1. The PIRS device shall be in full contact with the asphalt mixture contained in a sampling cylinder or be in full co
29、ntact with the pavement surface as shown in Figures 3 and 4, respectively. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c TP 128-5 AASHTO Figure 3PIRS Testing Module Attached to Sampling Cylinder
30、 Figure 4PIRS Testing of the In-Place Asphalt Pavement Surface 7.2. Testing with the PIRS device should only be done when the ambient temperature and moisture are within the allowable range based on the manufacturers recommendations. 7.3. Use the diffused reflectance mode for this procedure. 7.4. Th
31、e number of scans and scanning region of frequencies should be preset as prescribed by the PIRS manufacturer. A minimum of 24 scans in the region between 3800 and 1000 cm1wavenumbers is recommended. This device setup ensures testing time of one minute per test. 8. PROCEDURE 8.1. Collect the asphalt
32、mixture sample as described in Section 6. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c TP 128-6 AASHTO 8.2. Configure the PIRS device in accordance with Section 7 and the manufacturers recommen
33、dations. 8.3. Conduct testing utilizing the PIRS device. 8.4. Store the test results in a designated library or folder for further processing. 9. SPECTRAL DATA PROCESSING AND INTERPRETATION 9.1. Determination of Oxidation Signal Value: 9.1.1. For each test, the spectral data is represented on the Y-
34、axis by the infrared absorbance and on the X-axis by the corresponding wavenumbers (see Figure 5). 9.1.2. The absorbance values plotted against the wavenumber values create an absorbance spectrum for the sample. 9.1.3. Oxidation signal (OxS) value is calculated as shown in Equation 1. 17002920AOxSA=
35、(1) where: A1700 = peak value (maximum absorbance value) in the region between 1750 and 1650 cm1, which is associated with the benzylic ketone functional group most commonly present in oxidized asphalt. A2920 = peak value (maximum absorbance value) in the region between 2950 and 2850 cm1, which is a
36、ssociated with the aliphatic hydrocarbon chains present in all asphalts. This peak is also expected to be the highest of all the peaks associated with asphalt binder (Figure 5). Figure 5Example of Calculation of an OxS Value Note 3Location of the characteristic peaks on an absorbance spectrum can va
37、ry within 10 cm1from the values given in this method. 9.2. Interpretation of oxidation value data: 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c TP 128-7 AASHTO 9.2.1. The OxS data should be use
38、d for quality control purposes to compare the extent of oxidation in plant-produced and compacted samples against a control sample produced in accordance with a laboratory control mixture. For example, Figure 6 superimposes the mean and standard deviations for the OxS values obtained from the job mi
39、xture formula (JMF), plant, and the in-place pavement samples. The error bars shown are one standard deviation from the mean of five samples. The apparent overlap between the error bars in Figure 6 indicates that both plant and the in-place pavement measurements have OxS values well within a standar
40、d deviation from the mean JMF values. The control sample is the approved JMF and obtained from the mixture design laboratory. Figure 6Example of Comparison of Oxidation in JMF, Plant, and Pavement Samples 10. PRECISION AND BIAS 10.1. The coefficient of variation (CV) in measured oxidation indices fo
41、r one sample is established as a ratio of the standard deviation over the mean index value for at least five samples from the sample. If the CV exceeds 6 percent, additional samples should be taken to achieve this threshold. 11. REPORT 11.1. The report for this procedure should include the following
42、 items: 11.1.1. General project information, such as job site location and the type of material tested, in accordance with standard user or contractor protocols. 11.1.2. Testing parameters, such as instrument type/ID, ambient temperature, and temperature of sample before testing. 11.1.3. Mean A1700,
43、 A2920, and OxS values for each sample tested. 11.1.4. Mean and standard deviation for all samples of the same material such as RAP stockpile, pavement surface, plant-produced, and JMF. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication i
44、s a violation of applicable law.TS-2c TP 128-8 AASHTO 12. HAZARDS 12.1. This standard practice may employ toxic solvents for cleaning purposes. The user of the practice is referred to OSHA standard 29 CFR 1910 Subpart Z, Toxic and Hazardous Substances, for safety guidelines. 12.2. The user of the eq
45、uipment is referred to OSHA standard 1926 Subpart D, Occupational Health and Environmental Controls, for safety guidelines. 13. KEYWORDS 13.1. Absorbance spectrum; aging rate; asphalt mixture production; in-place pavement; job mix formula specimen; oxidation signal; peak value; portable infrared spe
46、ctrometer (PIRS). 14. REFERENCES 14.1. Petersen, J. Claine. A Transportation Research Circular E-C140: A Review of the Fundamentals of Asphalt Oxidation: Chemical, Physicochemical, Physical Property, and Durability Relationships. TRB, National Research Council, Washington, DC, October 2009. 14.2. Sa
47、lomon, D. and I. Yut. Improving Quality Control of Asphalt Pavement with RAP with the Use of Portable Infrared Spectroscopy Device. RP 249. Idaho Department of Transportation, Boise, ID, June 2016. 14.3. Smith, B. Infrared Spectral Interpretation: A Systematic Approach. CRC Press, Boca Raton, FL, 19
48、99. 14.4. Zofka A., M. Chrysochoou, I. Yut, M. Shaw, S-P. Sun, J. Mahoney, S. Farquharson, and M. Donahue. Evaluating Applications of Field Spectroscopy Devices to Fingerprint Commonly Used Construction Materials. SHRP 2 Project No. R06 (B), Report S2-R06B-RR-1. TRB, National Research Council, Washington, DC, 2013. 1This provisional standard was first published in 2017. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.
