1、Standard Method of Test for Determining the Interlayer Shear Strength (ISS) of Asphalt Pavement Layers AASHTO Designation: TP 114-171 Technical Section: 2c, AsphaltAggregate MixturesRelease: Group 3 (August 2017) American Association of State Highway and Transportation Officials 444 North Capitol St
2、reet N.W., Suite 249 Washington, D.C. 20001 TS-2c TP 114-1 AASHTO Standard Method of Test for Determining the Interlayer Shear Strength (ISS) of Asphalt Pavement Layers AASHTO Designation: TP 114-171Technical Section: 2c, AsphaltAggregate MixturesRelease: Group 3 (August 2017) 1. SCOPE 1.1. This tes
3、t method covers the determination of the interlayer shear strength of asphalt pavement layers using laboratory-prepared samples or core samples. 1.2. This test can be performed on 150-mm (6-in.) or 100-mm (4-in.) diameter specimens of asphalt pavement. 1.3. This test is applicable if the asphalt ove
4、rlay layer and the base layer are both 50 5 mm (2.0 0.2 in.) thick. The total specimen thickness must not exceed 150 mm (6 in.). Layers may be saw cut to the recommended layer thickness. 1.4. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to
5、address all safety concerns associated with its use. It is the responsibility of the user of this procedure to establish appropriate safety and health practices and to determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 231, Weighing D
6、evices Used in the Testing of Materials T 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor 3. TERMINOLOGY 3.1. interlayer shear strength (ISS)the maximum capacity of the interface to resist failure due to shearing stresses. 4. SUMMA
7、RY OF METHOD 4.1. The Louisiana Interlayer Shear Strength Tester (LISST) was developed for the characterization of interface shear strength of cylindrical specimens. The device (see Figure 1) consists of two main parts: a shearing frame and a reaction frame. Only the shearing frame is allowed to mov
8、e, while the reaction frame is stationary. A cylindrical specimen is placed inside the shearing and reaction 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c TP 114-2 AASHTO frames and is locked in
9、 place with collars. Loading is then applied to the shearing frame. As the vertical load is gradually increased, shear failure occurs at the interface. 5. SIGNIFICANCE AND USE 5.1. Tack coats are applied on a pavement surface before overlay construction to ensure adequate interface bond strength bet
10、ween two layers. If the interface cannot provide enough strength to resist stresses due to traffic and environmental loading, shear failure may occur at the interface. Poor interface bond strength may also accelerate the appearance of other distresses such as slippage and surface cracks. 6. APPARATU
11、S 6.1. Louisiana Interlayer Shear Strength Tester (LISST)The device used for the interlayer shear strength test shall be designed such that it adapts to most universal testing machines, has a nearly frictionless linear bearing to maintain vertical travel, accommodates sensors that measure the vertic
12、al and horizontal displacements, provides a specimen locking mechanism, applies consistent normal loads, and accommodates 100- or 150-mm (4- or 6-in.), or both, sample diameters. It is recommended that the clearance for the LISST device in the loading frame be 304.8 mm (12 in.). The gap between the
13、loading frame and the reaction frame shall be 12.7 mm (1/2in.). The device is illustrated in Figures 1 and 2. Figure 13-D Illustration of the Louisiana Interface Shear Strength Tester (LISST) Device 2017 by the American Association of State Highway and Transportation Officials. All rights reserved.
14、Duplication is a violation of applicable law.TS-2c TP 114-3 AASHTO Note: All dimensions are in millimeters. Figure 2Front and Side View o f the LISST Device 6.2. Loading MachineThe loading machine shall produce a uniform vertical movement of 2.54 mm (0.1 in.)/min. A universal mechanical or hydraulic
15、 testing machine may be used such that it can provide a displacement rate of 2.54 mm (0.1 in.)/min. The loading device shall be capable of meeting the minimum requirements specified in Table 1. Note 1Test results are expected to be d ifferent at different loading rates. Table 1Minimum Test System Re
16、quirements Range Accuracy (percent) Load, N (lbf) 025000 (5607) 1.0 Loading Ram LVDT, mm (in.) 0150 (5.9) 0.5 Vertical, Horizontal LVDTs, mm (in.) 02 (0.08) 0.5 6.3. Air CompressorCapable of supplying of 7.5 standard ft3/min (SCFM) at 40 psi to operate the pneumatic normal load actuator (optional).
17、6.4. Wet Masonry Saw. 6.5. Weighing DeviceThe weighing device shall have sufficient capacity, be readabl e to 0.1 percent of the sample mass or better, and conform to the requirements of M 231. 7. HAZARDS 7.1. Standard laboratory safety precautions must be observed when preparing and testing asphalt
18、 concrete specimens. CLCL304.8SensorBracketSensorSensorSet ScrewCamLockMechanismOutlet forSensor WiresPositionIndicator Slotfor Initial Set Point150.11Dia292.1114.3Linear BearingLoading Lock withSafety ProvisionCam LockMechanism12.5 DiaCoarseAdjustment Nut 2017 by the American Association of State H
19、ighway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c TP 114-3 AASHTO Note: All dimensions are in millimeters. Figure 2Front and Side View o f the LISST Device 6.2. Loading MachineThe loading machine shall produce a uniform vertical movement of
20、2.54 mm (0.1 in.)/min. A universal mechanical or hydraulic testing machine may be used such that it can provide a displacement rate of 2.54 mm (0.1 in.)/min. The loading device shall be capable of meeting the minimum requirements specified in Table 1. Note 1Test results are expected to be d ifferent
21、 at different loading rates. Table 1Minimum Test System Requirements Range Accuracy (percent) Load, N (lbf) 025000 (5607) 1.0 Loading Ram LVDT, mm (in.) 0150 (5.9) 0.5 Vertical, Horizontal LVDTs, mm (in.) 02 (0.08) 0.5 6.3. Air CompressorCapable of supplying of 7.5 standard ft3/min (SCFM) at 40 psi
22、to operate the pneumatic normal load actuator (optional). 6.4. Wet Masonry Saw. 6.5. Weighing DeviceThe weighing device shall have sufficient capacity, be readabl e to 0.1 percent of the sample mass or better, and conform to the requirements of M 231. 7. HAZARDS 7.1. Standard laboratory safety preca
23、utions must be observed when preparing and testing asphalt concrete specimens. CLCL304.8SensorBracketSensorSensorSet ScrewCamLockMechanismOutlet forSensor WiresPositionIndicator Slotfor Initial Set Point150.11Dia292.1114.3Linear BearingLoading Lock withSafety ProvisionCam LockMechanism12.5 DiaCoarse
24、Adjustment Nut 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c TP 114-4 AASHTO 8. TEST SPECIMENS 8.1. Test specimens may be either laboratory-compacted asphalt mixtures or sampled from asphalt pav
25、ements. 8.2. Samples Cored from Asphalt Pavement: 8.2.1. Mark the direction of traffic on the roadway surface before coring so that it can be identified once the core is removed. 8.2.2. Cores shall be taken full depth so that no prying action is needed to extract the cores from the pavement. Care sh
26、all be taken to avoid stress or damage to the interface during coring, handling, and transportation. If a core debonds at the interface of interest during the coring operation, acquire an additional core and make note of it on the coring report. 8.2.3. Clearly label the core specimens. Mark the dire
27、ction of travel with a straight line across the diameter parallel to the traffic flow. 8.2.4. Roadway core specimens shall be approximately 150 mm (6 in.) in diameter with all surfaces of the perimeter perpendicular to the surface of the core within 6 mm (1/4in.). If the height of the core above or
28、below the interface being tested is greater than 50 mm (2 in.), it shall be trimmed with a wet masonry saw to a height of approximately 50 mm (2 in.). 8.2.5. If the core specimen has more than one interface, clearly mark the joint to be tested just above or below the interface(s). 8.3. Laboratory-Co
29、mpacted Asphalt Mixture Samples: 8.3.1. The laboratory sample consists of two layers, top and bottom, with a tack coat at the interface of these layers. The diameter of each layer is 150 mm (6 in.). Compact the bottom layer of the sample to a height of 50 mm (2 in.) and an air void content of 6.0 1.
30、0 percent using the Superpave Gyratory Compactor (SGC) according to T 312. The amount of tack coat to be applied is determined by the desired application rate. Utilize a laboratory scale to ensure that the correct amount of tack coat is applied. Heat the tack coat material to the specified applicati
31、on temperature, and apply it to the surface of the bottom layer at the specified application rate using a 1-in. natural bristle brush. Allow the tack coat material to cure. Reheat the SGC mold, and place the compacted bottom layer in the mold. Place loose mix on top of the tack-coated bottom layer,
32、and compact the top layer to a height of 50 mm (2 in.) and an air void content of 6.0 1.0 percent using the SGC according to T 312. Note 2If the adjustment ram ends on the shear tester do not fully contact with the specimen, one or both ends of the specimen may be compacted to a height of 60 mm (2.4
33、 in.). Other means such as a steel spacer may be used on the adjustment ram(s). These modifications allow full contact with the specimen when consolidation pressure on both ends is required. 8.4. Measure the diameter of the specimen and the thickness of both layers to the nearest 1 mm (0.04 in.). 8.
34、5. Number of Test SpecimensA single test shall consist of at least three specimens. 9. PROCEDURE 9.1. Specimen ConditioningThe specimens shall be conditioned at the test temperature of 25 1C (77 2F) for a minimum of 2 h. 2017 by the American Association of State Highway and Transportation Officials.
35、 All rights reserved. Duplication is a violation of applicable law.TS-2c TP 114-5 AASHTO 9.2. Specimen PositioningOrient the core in the interlayer shear strength tester device so that the direction of traffic marked on the core is vertical. It is recommended that the top layer be placed on the shea
36、ring side. 9.3. The specimen should be loaded in such a manner that the interlayer is located directly in the middle of the gap between the loading and the reaction frames. The loading frame is the frame that can move up and down and the reaction frame is the stationary portion of the apparatus (see
37、 Figures 1 and 2). 9.4. Normal load, if required, can be applied by means of normal load actuator. The normal load actuator should be able to apply normal pressure up to 206.84 kPa (30 psi) on a 150-mm (6-in.) diameter specimen. 9.5. Rate of DisplacementApply the displacement continuously and withou
38、t shock, at a constant displacement rate of 2.54 mm (0.1 in.)/min until failure. Record the ultimate load applied to the specimen (Pult), and the vertical and horizontal deformations. A graph of a typical test result is shown in Figure 3. Figure 3Typical Test Results 10. CALCULATIONS 10.1. Calculate
39、 the interlayer shear strength, ISS, as follows: 24ultPISSD=where: ISS = interlayer shear strength, Pa; Pult= ultimate load applied to specimen, N; and D = diameter of test specimen, m. 11. REPORT 11.1. Report the following for each specimen tested: 11.1.1. Core identification and percent air voids.
40、 InterfaceShearLoad(lbf)0500150010000.0 0.2 0.4 0.6 0.8 1.0Displacement (in.)Pult 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-2c TP 114-6 AASHTO 11.1.2. Report the failure surface location. Failu
41、re should occur at the interface of the two material layers. 11.1.3. Note the appearance of the interface including any contaminants, milling striations, stripping, tack coat streaks, etc. 11.1.4. Specimen DimensionsIncluding thickness of the overlay asphalt, thickness of existing layer, and diamete
42、r of specimen. 11.1.5. Test Results: 11.1.5.1. Ultimate load applied, nearest 4.4 N (1 lbf). 11.1.5.2. Interlayer shear strength, nearest Pa (psi). 11.1.5.3. Corresponding vertical and horizontal deformations, mm (in.). 11.1.5.4. Average and standard deviation of interlayer shear strength for the se
43、t of cores. 12. PRECISION AND BIAS 12.1. The precision and bias statements for this method have not been determined. 13. KEYWORDS 13.1. Asphalt overlay; interlayer shear strength; shear strength; slippage failure; tack coat. 1This provisional standard was first published in 2015. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.
