1、Standard Method of Test for Determining the Interlayer Shear Strength (ISS) of Asphalt Pavement Layers AASHTO Designation: TP 114-151American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-2c TP 114-1 AASHTO Standard Metho
2、d of Test for Determining the Interlayer Shear Strength (ISS) of Asphalt Pavement Layers AASHTO Designation: TP 114-1511. SCOPE 1.1. This test method covers the determination of the interlayer shear strength of asphalt pavement layers using laboratory-prepared samples or core samples. 1.2. This test
3、 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 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 r
4、ecommended layer thickness. 1.4. This standard may involve hazardous materials, operations, and equipment. This standard does not purport to address all safety concerns associated with its use. It is the responsibility of the user of this procedure to establish appropriate safety and health practice
5、s and to determine the applicability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 231, Weighing Devices Used in the Testing of Materials T 312, Preparing and Determining the Density of Asphalt Mixture Specimens by Means of the Superpave Gyratory Compactor
6、3. TERMINOLOGY 3.1. Definition: 3.1.1. interlayer shear strength (ISS)the maximum capacity of the interface to resist failure due to shearing stresses. 4. SUMMARY OF METHOD 4.1. The Louisiana Interlayer Shear Strength Tester (LISST) was developed for the characterization of interface shear strength
7、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 the reaction frame is stationary. A cylindrical specimen is placed inside the shearing and reaction frames and is locked in place w
8、ith collars. Loading is then applied to the shearing frame. As the vertical load is gradually increased, shear failure occurs at the interface. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c TP 11
9、4-2 AASHTO 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 layers. If the interface cannot provide enough strength to resist stresses due to traffic and environmental loading, shear failure m
10、ay 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. Louisiana Interlayer Shear Strength Tester (LISST)The device used for the interlayer shear strength test shall be designed such that i
11、t adapts to most universal testing machines, has a nearly frictionless linear bearing to maintain vertical travel, accommodates sensors that measure the vertical and horizontal displacements, provides a specimen locking mechanism, applies consistent normal loads, and accommodates 100- or 150-mm (4-
12、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 frame and the reaction frame shall be 12.7 mm (1/2in.). The device is illustrated in Figures 1 and 2. 6.2. Loading MachineThe loading
13、 machine shall produce a uniform vertical movement of 2.54 mm (0.1 in.) per minute. Universal mechanical or hydraulic testing machine may be used such that it can provide a displacement rate of 2.54 mm (0.1 in.) per minute. The loading device shall be capable of meeting the minimum requirements spec
14、ified in Table 1. Note 1Test results are expected to be different 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 Compres
15、sorCapable of supplying of 7.5 standard cubic feet per minute (SCFM) at 40 psi to operate the pneumatic normal load actuator (optional). 6.4. Wet Masonry 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
16、to the requirements of M 231. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c TP 114-3 AASHTO Figure 13-D Illustration of the Louisiana Interface Shear Strength Tester (LISST) Device Note: All dime
17、nsions are in millimeters. Figure 2Front and Side View of the LISST Device 7. HAZARDS 7.1. Standard laboratory safety precautions must be observed when preparing and testing asphalt concrete specimens. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved
18、. 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 HMA or sampled from HMA pavements. 8.2. Samples Cored from Asphalt Pavement: 8.2.1. Mark the direction of traffic on the roadway surface before coring so that
19、 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, handling, and transportation. If a core debonds at the inter
20、face of interest during the coring operation, acquire additional core and make note of it on the coring report. 8.2.3. Label core specimens with a paint pen. 8.2.4. Roadway core specimens shall be approximately 150 mm (6 in.) in diameter with all surfaces of the perimeter perpendicular to the surfac
21、e 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 shall be trimmed with a wet masonry saw to a height of approximately 50 mm (2 in.). 8.2.5. Mark the location of the interface layer with white or silver paint. 8.
22、3. Laboratory-Compacted 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.) at the target air
23、 voids 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 application
24、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, and
25、 compact the top layer to a height of 100 mm (4 in.) to the target air voids. 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 test shall consist of at least three specimens. 9. PROCEDURE 9.1. Specimen Co
26、nditioningThe specimens shall be conditioned at the test temperature of 25 1C (77 2F) for a minimum of 2 h. 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
27、 placed on the shearing 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
28、 the apparatus (see Figures 1 and 2). 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-2c TP 114-5 AASHTO 9.4. Normal load, if required, can be applied by means of normal load actuator. The normal load
29、 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 rate of 2.54 mm (0.1 in.) per minute until failure. Record the ultimate load a
30、pplied 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, as follows: 24ultPISSD=where: ISS = interlayer shear strength, Pa; Pul
31、t= 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. 11.1.2. Report the failure surface location. Failure should occur at the interface of the two material lay
32、ers. 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. InterfaceShearLoad(lbf)0500150010000.0 0.
33、2 0.4 0.6 0.8 1.0Displacement (in.)Pult 2015 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 11.1.5. Test Results: 11.1.5.1. Ultimate load applied, nearest 4.4 N (1 lbf). 11.1.5.2. Inter
34、layer 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 12.1. The precision and bias statements for this method have not been det
35、ermined. 13. KEYWORDS 13.1. Asphalt overlay; interlayer shear strength; shear strength; slippage failure; tack coat. 1This provisional standard was first published in 2015. 2015 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.
