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C-1 Proposed AASHTO Standard Method of Test for Evaluating the Shear Resistance of Asphalt-Treated Recycled Pavement Applications Using a Long-Pin Fixture A P P E N D I X C Standard Method of Test for Evaluating Shear Resistance of Asphalt-Treated Recycled Pavements Applications Using a Long-Pin Fixture AASHTO Designation: TP XXX-XX ASTM Designation: E XXXX-XX 1. SCOPE 1.1. This standard covers the determination of shear resistance of asphalt-treated cold recycled pavements through the number of blows and shear torque values with a long-pin shear test. In this test method, the long-pin shear fixture is driven into a pavement using a dynamic cone penetrometer (DCP) upper assembly (an 8-kg [17.6-lb] hammer) per ASTM D 6951 - 18, and the number of blows required to drive the fixture into the pavement is recorded. The DCP upper assembly is removed and the peak torque observed while rotating a handheld torque wrench connected to the long-pin shear fixture while the number of blows is recorded. These measurements can be used to make time-critical decisions regarding opening to traffic and surfacing of the recycled pavements. 1.2. This test method is applicable for number of blows and torque measurements conducted on asphalt-treated cold pavement recycling techniques, including cold in-place recycling (CIR), cold central-plant recycling (CCPR), and full-depth reclamation (FDR). The recycled pavements may include emulsified or foamed asphalt with or without active fillers such as cement, lime, and fly ash. 1.3. The values stated in SI units are to be regarded as the standard. The values in parentheses are provided for information purposes only. 1.4. 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 establish appropriate safety and health practices and determine the applicability of regulatory regulations prior to use.
C-2 2. REFERENCED DOCUMENTS 2.1. ASTM Standards: - D 6951/D 6951M - 18, Standard Test Method for Use of the Dynamic Cone Penetrometer in Shallow Pavement Applications - C1067 - 12 Standard Practice for Conducting a Ruggedness Evaluation or Screening Program for Test Methods for Construction Materials - C670 - 15 Standard Practice for Preparing Precision and Bias Statements for Test Methods for Construction Materials - C802 - 14 Standard Practice for Conducting an Interlaboratory Test Program to Determine the Precision of Test Methods for Construction Materials 3. TERMINOLOGY 3.1. Definitions: - Shear resistance â resistance of a recycled pavement to shear stress induced by rotation of a long-pin fixture driven into the pavement and rotated with a torque wrench 4. SUMMARY OF METHOD 4.1. The long-pin shear fixture is driven into compacted asphalt-treated cold recycled pavement by lifting the sliding hammer of the upper assembly of a DCP to the handle and then dropping it. The total number of blows to drive the fixture into the compacted recycled pavement is counted and recorded. The long-pin fixture, embedded in the compacted recycled pavement, is then twisted using a digital handheld wrench. The peak torque in a clockwise rotation is recorded in ft-lb, or any other unit of measure as appropriate. Three replicate tests are conducted on different locations of the same pavement of interest. 5. SIGNIFICANCE AND USE 5.1. Number of blows counted from dropping the hammer and torque measured using handheld wrench provide information that can be used to assess mixture shear resistance and make time-critical decisions regarding opening to traffic and surfacing of the recycled pavements. 6. APPARATUS 6.1. Handheld digital torque wrench: a torque wrench at least 305-mm [12-in.] in length with a digital display that can measure torque over a range of 15â300 ft-lbs with accuracy of Â±1.0% to which a 19--mm [0.75-in.] socket may be attached. 6.2. The long-pin shear fixture is shown schematically in Fig. 1. It consists of a steel base plate with circular geometry: 127-mm [5.0-in.] diameter), four 10.3-mm [0.406-in.] diameter and 80-mm [3.15-in.] long pins, one 12.7-mm [0.50-in.] diameter and 75-mm [2.95-in.] pin in the center of the steel base plate, one 25.4-mm [1.00- in.] diameter upper center shaft with a hexagonal milled end. 6.3. Test template for measurement shown in Fig. 2 and illustrated with the other equipment. 6.4. The hammer used in this test method shall conform to the general requirements described in ASTM D 6951/D 6951M - 18. An 8-kg [17.6-lb] DCP hammer (upper assembly) is shown schematically in Fig. 3. This device is typically constructed of stainless steel conforming to ASTM D 6951/D6951M - 18. - Hammer weight measurement of 8.0 kg [17.6-lb]; tolerance is 0.01 kg [0.02-lb]. - Drop of hammer measurement of 575 mm [22.6 in.]; tolerance is 1.0 mm [0.04 in.]. - Hammer weight measurement of 8.0 kg [17.6 lb]; tolerance is 0.01 kg [0.02 lb]. - Drop of hammer measurement of 575 mm [22.6 in.]; tolerance is 1.0 mm [0.04 in.].
C-3 FIG. 1 Schematics of the long-pin shear fixture. 1.000 2. 00 0 1.000 0.750 Ã1.000 2. 80 0 0.750 0. 50 0 0. 80 0 2. 00 0 3. 00 0 0.500 0.500Ã5.000 Ã.250 THRU Ã.531 .250 Ã.625 THRU Ã1.125 .050 Ã4.000 0.750 0. 80 0 0. 75 0 3. 05 0 0.500 3. 00 0 3. 00 0 0.406 0.406 37.5Â° 37.5Â° 5. 00 0 3. 25 0 FIG 2. Template used for torque measurement. 4 inches Shear or raveling fixture
C-4 FIG. 3 Schematic of upper hammer assembly. 7. HAZARDS 7.1. Injury can occur while operating DCP upper assembly (hammer) due to lifting and dropping the falling weight. Thus, care must be taken to avoid injury. 8. PROCEDURE 8.1. Place the long-pin fixture on the recycled pavement surface. To ensure uniform contact and load distribution of the steel base plate, the test surface should be smooth to the extent possible, and free of any loose material. 8.2. The DCP hammer (upper assembly) is then placed on top of the test fixture. The hammer-fixture system should be leveled using a bubble level resting on the base plate prior to testing. 8.3. The DCP hammer is lifted to the standard drop height and then released to deliver the force that drives the fixture into the recycled pavement. During the operation, the hammer weight guide shaft should be held firmly without applying any downward pressure. 8.4. Repeat lifting and releasing the weight until the long pins of the fixture are fully embedded into the recycled pavement and the base plate is resting on the pavement surface. The fixture handle should be plumb with respect to the pavement surface; change the test location if it is not plumb. 8.5. Record the number of blows required to drive the test fixture until the bottom of the steel plate is uniformly in contact with the recycled pavement surface. Remove the DCP upper assembly. 8.6. Attach a digital handheld torque wrench device to the upper shaft of the fixture using a 19-mm (0.75-in.) socket. 8.7. On the pavement surface, draw a 12-in. line extending from the center of the base plate. Next, draw a 4-in. line perpendicular to the 12-in. line at the end furthest from the base plate. 8.8. Rotate the torque wrench clockwise through the 4-in. [304.8-mm] line at a constant rate over a 4 second period. 8.9. Record the maximum torque observed as expressed in ft-lbs. 8.10. Repeat steps 8.1â8.9 at three (3) replicate locations with a center-to-center spacing of approximately 1 ft and far enough apart from prior measurements that each measurement is not influenced by the disturbed recycled pavement surface. An example of test locations for shear and raveling resistance is shown in Figure 4. 3 ft 2 ft Raveling 1 Shear 1 Raveling 2 Shear 2 Raveling 3 Shear 3 FIG. 4 Illustration of rapid test locations.
C-5 9. Reporting 9.1. Report the following information: 9.1.1. Test date, test location, lane, weather, recycling process, recycling agent, recycling agent content, active filler, active filler content, lane, offset, test number, number of blows, torque, nuclear density gauge reading. 9.2. Report the individual number of blows as whole numbers and torque measurements to 0.1 ft-lbs. Report the average of three number of blows measurements and three torque measurements to the nearest 0.1 blows or 0.1 ft-lbs, respectively. 10. PRECISION AND BIAS 10.1. A ruggedness evaluation was performed for this test method in accordance with ASTM C1067 - 12, Standard Practice for Conducting a Ruggedness Evaluation or Screening Program for Test Methods for Construction Materials. The tolerances on the long-pin shear fixture in Section 6. Apparatus was determined by the ruggedness study. A partial interlaboratory study was conducted in accordance with ASTM C802, Standard Practice for Conducting an Interlaboratory Test Program to Determine the Precision of Test Methods for Construction Materials. However, only three laboratories participated. This was because the test is new, and commercially available equipment was not available. The ILS was conducted in the field, rather than in a laboratory, as prescribed in ASTM C802 - 14. Thus, preliminary single-operator and multi-laboratory precision that can be found in NCHRP Research Report 960 are reported, which should be replaced with an ILS when commercially available equipment is available. 10.2. Number of Blows Single-Operator PrecisionâThe single-operator standard deviation was found to be 1.6 blows. Therefore, results of two properly conducted tests by the same operator on the same material are not expected to differ by more than 5 blows.A Multi-laboratory PrecisionâThe multi-laboratory standard deviation was found to be 2.6 blows. Therefore, results of two properly conducted tests by two different laboratories on specimens of the same material are not expected to differ by more than 7 blows.A AThese numbers represent the difference limits (d2s) as described in ASTM Practice C670. Note 1âThese precision statements are based on an interlaboratory study that involved three laboratories, six materials, and three replicate tests per operator, with number of blows values ranging from nine to 54. 10.3. Torque Value Single-Operator PrecisionâThe single-operator standard deviation was found to be 8.1 ft-lbf. Therefore, results of two properly conducted tests by the same operator on the same material are not expected to differ by more than 22.6 ft-lbf.A Multi-laboratory PrecisionâThe multi-laboratory standard deviation was found to be 12.7 ft-lbf. Therefore, results of two properly conducted tests by two different laboratories on specimens of the same material are not expected to differ by more than 35.7 ft-lbf.A AThese numbers represent the difference limits (d2s) as described in ASTM Practice C670. Note 2âThese precision statements are based on an interlaboratory study that involved three laboratories, six materials, and three replicate tests per operator, with torque values ranging from 39.5 ft-lbf to 165.6 ft-lbf. 10.4. Biasâbecause there is no accepted reference material suitable for determining the bias in this test method, no statement on bias is made. 11. KEYWORDS 11.1. Shear resistance; asphalt-treated recycled pavement, long-pin shear fixture, number of blows; torque; dynamic cone penetrometer (DCP); cold in-place recycling (CIR); cold central-plant recycling (CCPR); full-depth reclamation (FDR); sliding hammer; driving force; destructive testing; recycled pavement testing; recycled pavement layer shear resistance.