1、Standard Method of Test for Density of In-Place Hot Mix Asphalt (HMA) Pavement by Electronic Surface Contact Devices AASHTO Designation: T 343-121American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2c T 343-1 AASHTO St
2、andard Method of Test for Density of In-Place Hot Mix Asphalt (HMA) Pavement by Electronic Surface Contact Devices AASHTO Designation: T 343-1211. SCOPE 1.1. This method covers the in-place determination of the total density and relative compaction of HMA pavements by measuring changes in the electr
3、omagnetic field resulting from the compaction process. 1.2. The equipment referenced in this method is an electronic surface contact device that is relatively unaffected by the surface moisture and surface variances in temperatures typically encountered during HMA paving operations. If needed, it sh
4、ould include circuitry to measure/compensate for moisture and temperature variances during the material compaction process. 1.3. This procedure does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this procedure to establish appropri
5、ate safety and health practices and determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standard: T 166, Bulk Specific Gravity (Gmb) of Compacted Hot Mix Asphalt (HMA) Using Saturated Surface-Dry Specimens 3. SIGNIFICANCE 3.1. The test method descr
6、ibed is useful as a rapid nondestructive technique for determining the in-place density and relative compaction of compacted HMA mixtures. 3.2. The density results obtained by this test method may be applied using three method applications, Method ARelative, Method BScreed Calibration, and Method CC
7、ore Calibration. Method C is the most accurate and requires a correlation with a known density sample of the material being measured. 4. INTERFERENCES 4.1. The composition of the HMA mix being tested may significantly affect the measurements. The device should be calibrated to the specific mix desig
8、n being used in the field. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c T 343-2 AASHTO 4.2. This test method may exhibit spatial bias. Oversize aggregate particles in the area of the sensor path
9、 may cause variations in density readings. The average of at least four measurements at each test location is recommended. 4.3. The surface texture of the material being tested may cause lower than actual density readings. 4.4. Electromagnetic force fields, such as those caused by overhead high-tens
10、ion power lines or large metal objects near the device, may interfere with the device reading. 5. APPARATUS 5.1. The device shall meet requirements outlined below: 5.2. The device shall be housed in an enclosure of heavy-duty construction, and designed for taking in situ density measurements of HMA
11、pavements. 5.3. The device shall function at the temperature and moisture levels experienced during the placement of HMA pavements. 5.4. The device shall include the internal circuitry suitable for displaying individual measurements to allow operators to record the results. 5.5. The device shall inc
12、lude a continuous measurement mode of operation. 5.6. The device shall employ suitable electronic circuitry to provide power and signal conditioning to the sensor to provide the data acquisition and readout function, and allow calibration of the unit over the expected range of application conditions
13、 and materials. 6. TEST SITE PREPARATION 6.1. Because surface conditions can have a significant effect on density measurements, a smooth surface with no excess water (roller water is acceptable) is required for proper testing. The optimum condition for general testing would be a dry, smooth surface,
14、 with total contact between the bottom surface of the device and the surface being tested. 6.2. Select a flat, relatively smooth test area on the HMA mat. Brush the surface clear of any sand or stones that would prevent contact between the surface and the measuring device. 7. CALIBRATION PROCEDURE 7
15、.1. Calibrate the device for each mixture prior to performing tests on materials that are different from the material types used in establishing the most recent calibration. Calibrate a newly acquired or repaired device. If available, a standard plate or reference base shall be used to ensure that t
16、he device is within the manufacturers specifications. 7.2. The device should be calibrated on the HMA mat at compaction temperature ranges allowing subsequent readings to be taken as paving progresses at this temperature range. For calibration using core samples, follow the procedure in Section 7.4.
17、3 and refer to the manufacturers recommended procedures. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c T 343-3 AASHTO 7.3. Maneuver the device as per the manufacturers recommendations. Several si
18、ngle measurements are averaged to calculate a reading. The location and number of measurements used to calculate a reading will depend on the manufacturers specifications. 7.4. Calibrate the device following the procedure for Method A, B, or C. All data used for calibration shall be recorded for eac
19、h mix formula. 7.4.1. Method AThis is the relative method. It may be used to track the compaction process during the establishment of roller patterns. 7.4.1.1. Place the device on the asphalt mat at the test location, draw an outline around the probe of the unit, and record compaction measurements a
20、nd average reading of the uncompacted material exiting the screed. 7.4.1.2. After each roller pass, place the device within the outline and record compaction measurements and average reading. 7.4.1.3. When readings no longer increase with additional passes, record this value and the number of passes
21、. 7.4.1.4. Repeat the steps in Sections 7.4.1.2 and 7.4.1.3 after each roller type where compaction is to be monitored. 7.4.2. Method BThis is the screed calibration method. It utilizes the percent compaction obtained by the screed to calculate a starting density. This method requires the operator t
22、o estimate the percent compaction obtained by the screed; routinely this number is 75 to 85 percent of the maximum theoretical or voidless density. Operator experience will contribute to the accuracy of the compaction estimate and the success of this method. 7.4.2.1. Estimate the percent compaction
23、obtained by the screed. 7.4.2.2. Multiply the maximum theoretical density of the material by the percent compaction obtained by the screed, in decimal form. Example: The voidless density is 2468 kg/m3(154 pcf); the screed compaction is 0.81 percent. The gauge should read 1999 kg/m3(124.7 pcf) behind
24、 the screed (2468 0.81 = 1999 kg/m3). 7.4.2.3. Measure the density of the mixture exiting the screed and offset the device to obtain the reading calculated in Section 7.4.2.2. Follow the manufacturers specific recommendations to input the offset. 7.4.3. Method CThis is the core calibration method. I
25、t uses actual core densities to calibrate the device. This is the most accurate and detailed method and should be reviewed for a general understanding of the calibration process. 7.4.3.1. Identify one to five test locations on the HMA mat. For establishing a control strip, five core locations should
26、 be used. For pavement monitoring or quality control, the operators discretion and manufacturers recommendations should be followed. 7.4.3.2. Place the device on the asphalt mat at the test location and draw an outline around the probe of the unit. Record the measurements and average reading. 7.4.3.
27、3. Cut a 150-mm (6-in.) diameter core from the area within the device outline where the reading was taken. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c T 343-4 AASHTO 7.4.3.4. Repeat the steps i
28、n Sections 7.4.3.2 and 7.4.3.3 at additional test locations, if applicable. 7.4.3.5. In the laboratory, determine the density of each 150-mm (6-in.) diameter core in accordance with T 166 or other applicable methods, and record the results. 7.4.3.6. Record the numeric difference between the average
29、reading obtained with the device and the corresponding core density for each test location. 7.4.3.7. Average the numeric differences from Section 7.4.3.6 and record the average numeric difference. 7.4.3.8. Adjust the device, following the manufacturers procedures, to account for the average numeric
30、difference. This will calibrate the instrument to the asphalt mat by adding (or subtracting) the average numeric difference. 8. PROCEDURE OF OPERATION 8.1. Ensure that the device is calibrated in accordance with Section 7 of this specification for the site conditions and HMA mixture being used. 8.2.
31、 Locate the measurement area away from any known sources of electromagnetic interference such as overhead high-tension power lines or large metal objects. For best results, avoid surfaces with large temperature extremes. 8.3. Place the device firmly on the test surface (prepared in accordance with S
32、ection 6 of this standard) and trace an outline around the probe (base) of the unit. 8.4. Record the density measurements given by the device. For quality control or pavement monitoring, the number of measurements taken at a location is less critical. More measurements are required when quality assu
33、rance applications or where companion cores will be taken. The number of measurements required will depend on the manufacturers recommendation based on the device capabilities. The number of measurements should be supported with precision statements obtained from similar sites. 8.5. Average the meas
34、urements from an individual location to obtain an average density reading. 8.6. Record data in accordance with Section 9 of this standard. 9. RECORDING RESULTS 9.1. Job site identification and test site location data in accordance with standard contractor protocols. 9.2. Device calibration data as s
35、pecified in Section 7. 9.3. Immediately Record: 9.3.1. Individual density measurements at each test location, together with the calculated average density reading for the location; 9.3.2. Temperature of the HMA mat at the time of readings, if taken; 2015 by the American Association of State Highway
36、and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c T 343-5 AASHTO 9.3.3. Any qualitative observations of testing or material conditions that may affect the accuracy or interpretation of test results; 9.3.4. Corresponding core density data (if taken)
37、for each test location; and 9.3.5. Dated signature by the test operator. 1Formerly AASHTO Provisional Standard TP 68. First published as a full standard in 2012. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
