1、Standard Method of Test for Determining the Interlayer Shear Strength (ISS) of Asphalt Pavement Layers AASHTO Designation: TP 114-181Technical Section: 2c, AsphaltAggregate Mixtures Release: Group 3 (August) American Association of State Highway and Transportation Officials 444 North Capitol Street
2、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 114-181Technical Section: 2c, AsphaltAggregate Mixtures Release: Group 3 (August) 1. SCOPE 1.1. This test method
3、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 overlay laye
4、r 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 address a
5、ll 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 Devices Us
6、ed 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. SUMMARY OF MET
7、HOD 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 move, while
8、the reaction frame is stationary. A cylindrical specimen is placed inside the shearing and reaction 2018 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 place wi
9、th 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 between two
10、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. APPARATUS 6.1. Lo
11、uisiana 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 vertical and ho
12、rizontal 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 loading f
13、rame 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 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplicati
14、on is a violation of applicable law.TS-2c TP 114-3 AASHTO Note: All dimensions are in millimeters. Figure 2Front and Side View of 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 testing m
15、achine 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 different at different loading rates. Table 1Minimum Test System Requirements
16、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). 6.4. Wet Ma
17、sonry Saw. 6.5. Weighing DeviceThe weighing device shall have sufficient capacity, be readable 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 concrete sp
18、ecimens. CLCL304.8SensorBracketSensorSensorSet ScrewCamLockMechanismOutlet forSensor WiresPositionIndicator Slotfor Initial Set Point150.11Dia292.1114.3Linear BearingLoading Lock withSafety ProvisionCam LockMechanism12.5 DiaCoarseAdjustment Nut 2018 by the American Association of State Highway and T
19、ransportation 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 pavements. 8.2. Samples Cored from Asphalt Pavement: 8.2.1. Mark the dire
20、ction 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 shall be taken to avoid stress or damage to the interface during coring,
21、 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 direction of travel with a straight line across the diameter parallel to t
22、he 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 below the interface being tested is greater than 50 mm (2 in.), it sha
23、ll 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-Compacted Asphalt Mixture Specimens: 8.3.1. The laboratory specimen cons
24、ists 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 specimen to a height of 50 mm (2 in.) and an air void content of 6.0 1.0 percent using the Superpave Gyratory Compactor (SGC) according
25、 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 application temperature, and apply it to the surface of the bottom layer
26、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, and compact the top layer to a height of 50 mm (2 in.) using the
27、 SGC according to T 312. Ensure the air void content of the entire specimen is 6.0 1.0 percent. 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 in.). Other means such as a steel s
28、pacer 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.). 8.5. Number of Test SpecimensA single
29、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. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is
30、 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 shearing side. 9.3. The specimen should
31、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 Figures 1 and 2). 9.4. Normal load,
32、 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 without shock, at a constant displacement
33、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 the interlayer shear strength, ISS,
34、 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. InterfaceShearLoad(lbf)050015001000
35、0.0 0.2 0.4 0.6 0.8 1.0Displacement (in.)Pult 2018 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. Failure should occur at the interface of
36、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 diameter of specimen. 11.1.5. Test Results:
37、 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 set of cores. 12. PRECISION AND BIAS 1
38、2.1. 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. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.
