1、Proposed Standard Test Method for Determining the Dynamic Modulus of Asphalt Mixtures Using the Indirect Tension Test AASHTO Designation: TP 131-18 Technical Section: 2d, Bituminous Materials Release: Group 3 (August) American Association of State Highway and Transportation Officials 444 North Capit
2、ol Street N.W., Suite 249 Washington, D.C. 20001 TS 2d TP 131-1 AASHTO Proposed Standard Test Method for Determining the Dynamic Modulus of Asphalt Mixtures Using the Indirect Tension Test AASHTO Designation: TP 131-18 Technical Section: 2d, Bituminous Materials Release: Group 3 (August) 1. SCOPE 1.
3、1. This standard describes the test method for measuring the dynamic modulus of asphalt mixtures using the indirect tension test. This practice is intended for dense- and gap- graded mixtures with nominal maximum aggregate sizes up to 25 mm. 1.2. This standard may involve hazardous materials, operat
4、ions, and equipment. This standard does not purport to address all of the safety problems 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 its use
5、. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standard: PP 95, Preparation of Indirect Tension Performance Test Specimens 2.2. Other Publications: Equipment Specification for the Simple Performance Test System, Version 3.0, Prepared for National Cooperative Highway Research Program (NCHRP), October 16, 2007
6、. Barksdale, R.D., J. Alba, N.P. Khosla, Y.R. Kim, P.C. Lambe, and M.S. Rahman. Laboratory Determination of Resilient Modulus for Flexible Pavement Design, Final Report, National Cooperative Highway Research Program 1-28 Project, June 1997. Chapra, S.C. and R.P. Canale, Numerical Methods for Enginee
7、rs, McGraw-Hill, 2009. Kim, Y.R., Y. Seo, M. King, and M. Momen. Dynamic Modulus Testing of Asphalt Concrete in Indirect Tension Mode. In Transportation Research Record: Journal of the Transportation Research Board, No. 1891, TRB, National Research Council, Washington, D.C., 2004. Lacroix, A., A. A.
8、 Mosavi Khandan, Y. R. Kim. Predicting the Resilient Modulus of Asphalt Concrete from the Dynamic Modulus. In Transportation Research Record: Journal of the Transportation Research Board, TRB, National Research Council, Washington, D.C., 2007. 3. TERMINOLOGY 3.1. Dynamic Modulusa linear viscoelastic
9、 material property that describes the stiffness of asphalt mixture at different frequencies and temperatures. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS 2d TP 131-2 AASHTO 3.2. Phase Angle, the
10、angle in degrees between a sinusoidal applied stress and the resulting strain in the same direction (vertical or horizontal). 3.3. Poissons Ratiothe ratio of the strain transverse to the loading direction (horizontal strain), divided by the axial strain (vertical strain). 3.4. Permanent Deformationn
11、on-recovered deformation in a repeated load test. 3.5. Indirect Tension (IDT)a method of loading a material by applying a compressive force on a cylindrical specimen in one direction, which results in a tensile stress and strain in the perpendicular direction due to the Poissons effect. 3.6. LVDT Co
12、mponents 3.6.1. Rodthin, stainless steel bar that holds the LVDT core. 3.6.2. Coremagnetic component of LVDT that attaches to rod. 3.6.3. Head-component that surrounds the core to measure the displacement. 3.6.4. Targetcomponent glued to the specimen to hold the LVDT rod and head away from the surfa
13、ce of the specimen. 4. SUMMARY OF THE TEST METHODS 4.1. This test method describes procedures for measuring the dynamic modulus from the indirect tension test for asphalt mixtures. 4.2. In the dynamic modulus procedure, an asphalt mixtures specimen, at a specific test temperature, is subjected to co
14、ntrolled sinusoidal (haversine) compressive stress in the vertical axis at various frequencies. The applied stresses and resulting axial and transverse strains are measured as a function of time and used to calculate the dynamic modulus, phase angle, and Poissons ratio. 5. SIGNIFICANCE AND USE 5.1.
15、The dynamic modulus is a performance related property that can be used for mixture evaluation and for characterizing the stiffness of asphalt mixtures for mechanistic-empirical pavement design. 6. APPARATUS 6.1. Specimen Fabrication EquipmentEquipment for fabricating dynamic modulus test specimens a
16、s described in AASHTO PP 95, Preparation of Indirect Tension Performance Test Specimens. 6.2. Dynamic Modulus Test SystemA dynamic test system meeting the requirements of Equipment Specification for the Simple Performance Test System, Version 3.0. A servo-hydraulic testing machine capable of produci
17、ng a controlled haversine compressive loading shall be used. The testing machine should have a capability of applying a sinusoidal load over a range of frequencies from 0.1 to 25 Hz and load level up to 25.0 kN. For sinusoidal loads, the standard error of the applied load shall be less than 5%. 6.3.
18、 Conditioning ChamberAn environmental chamber for conditioning the test specimens to the desired testing temperature. The environmental chamber shall be capable of controlling the 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a vi
19、olation of applicable law.TS 2d TP 131-3 AASHTO temperature of the specimen over a temperature range from -10 to 35C to an accuracy of 0.5C. The chamber shall be large enough to accommodate the load guide device and a dummy specimen with a temperature sensor mounted in the center for temperature ver
20、ification. 6.4. Load Guide Device (LGD)The loading device should be capable of testing 150 9 mm diameter specimens of thicknesses of 38 to 50 mm. An example of the Load Guide Device is shown in Figure 1. 6.4.1. The device should be compact enough to be used within the environmental chamber. It shoul
21、d have a fixed bottom loading plate and a moving upper loading plate. The movement of the upper plate should be guided by two columns, one on each side of the specimen and equidistant from the loading axis and the loading strips, to ensure it has minimal translational or rotational motion during loa
22、ding of the specimen. The guide columns shall have a frictionless bearing surface that shall be kept well lubricated. The surface of the guide columns shall be frequently inspected for any grooves caused due to friction. 6.4.2. Alignment of the device, within the loading system, shall be achieved so
23、 that such friction is limited to the minimum possible extent. The upper plate shall be rigid enough to prevent any deflections during loading. If heavyweight plates are used to achieve rigidity, the testing should be able to counteract all the weight, such that no more than 8.9 N of load is transfe
24、rred to the specimen when the load is not being applied. It is recommended that high-strength material be used to achieve rigidity and keep the weight small. The loading strips preferably shall be perpendicular to the line connecting the two guide columns, so that visual alignment of the sample in t
25、he device is easier. (a) (b) Figure 1Two post load guide device with specimen prepared for testing: (a) front view and (b) side view 6.5. Loading StripsSteel loading strips, with concave sample contact surfaces, are required to apply load to the test specimens. 2018 by the American Association of St
26、ate Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS 2d TP 131-4 AASHTO 6.5.1. The loading strips shall be machined to the radius of curvature of 150 0.15 mm. The contact arc of the loading strip shall be between 12.5 mm and 19 mm. The outer
27、edges of the curved surface shall be filed lightly to remove sharp edges that might cut the specimen during testing. Thin lines should be drawn along the length of the strip at its center, to help in alignment. 6.6. Specimen Deformation Measurement DevicesThe specimen deformation measurement devices
28、 shall consist of four displacement transducers with a range of at least 0.25 mm, and a minimum resolution throughout the range of 0.10 m. 6.7. LVDT Target Alignment DeviceAn alignment device shall be used to position and place the vertical and horizontal LVDT targets and hold them there until the g
29、lue cures. An example LVDT target alignment device is shown in Figure 2, and its schematic views with pertinent dimensions are presented in Figure 3. 6.7.1. The device shall be easily removable, without disturbing the LVDT targets or the specimen once the glue cures. The device shall preferably have
30、 the capability to mount the LVDT targets at different gauge lengths. The LVDT heads and rods shall be close, but not touching, the surface of the specimen to minimize possible damage due to bulging of the specimen under loading. To ensure uniform test results, a height of 5 mm from the surface of t
31、he specimen is recommended. 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS 2d TP 131-5 AASHTO Figure 2Example alignment device (a) assembled, (b) base with sliding holder, (c) bottom of top plate wi
32、th cross for alignment of LVDT holders, and (d) top of top plate (a) (b) (c) (d) 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS 2d TP 131-6 AASHTO Top View of Bottom Plate Bottom View of Top Plate 1
33、9.1 mm diam., 12.7 mm long steel rod19.1 mm diam., 127.0 mm long steel rodWing nut57.2 mm6.4 mm x 6.4 mm slotsspaced 16.5 mm on center25.4 mm x 19.1 mm x 6.4 mm spacer 71.1 mm25.4 mm x 25.4 mm x 88.9 mm angle71.1 mm x 44.5 mm x 3.2 mm slotted plate4.8 mm diam. roll pins spaced 12.7 mm on center proj
34、ecting 3.2 mm out of the plateConcentric cut outs for a geared axle w/ thumb knob7.2 mm diam., 7.1 mm deep holes spaced 31.8 mm and 50.8 mm respectively from the central hole4.8 mm diam., 4.8 mm deep central hole228.0 mm203.2 mm114.3 mm228.0 mm4.8 mm diam. roll pins spaced 12.7 mm on center, w/ 4.1
35、mm projecting out of the plate25.4 mm OD, 19.1 mm ID, 47.4 mm tall brass bushings12.7 mm x 12.7 mm x 12.7 mm alignment cube drilled with holes. Attached to thumb screws on the opposite side of the plate 2018 by the American Association of State Highway and Transportation Officials. All rights reserv
36、ed. Duplication is a violation of applicable law.TS 2d TP 131-7 AASHTO Top View of the Clamping Arm Assembly Side View of the Alignment Device Figure 3Schematic views of the alignment device 6.8. Stiff Specimen150 mm diameter by 38 to 50 mm thick specimen for use in aligning the loading platens in t
37、he dynamic modulus. A good material for this purpose is aluminum. 74.4 mm101.6 mm88.9 mm x 88.9 mm x 55.1 mm angle12.2 mm deep, x 12.7 mm wide rounded cutouts6.4 mm x 6.4 mm (0.25” x 0.25”) x 203.2 mm gear racksgeared axle w/ thumb knob25.4 mm x 31.8 mm x 3.4 mm plate71.1 mm x 44.5 mm x 3.2 mm slott
38、ed platewing nuts25.4 mm x 25.4 mm x 88.9 mm angle25.4 mm x 19.1 mm x 6.4 mm spacer 25.4 mm OD, 19.1” ID, 47.4 mm tall brass bushingsThumb screw attached to alignment cube4.8 mm diam. roll pins spaced 12.7 mm on center, w/ 4.1 mm” projecting out of the plateclamping arm assembly19.1 mm thick top pla
39、te19.1 mm thick bottom plategeared axel w/ thumb knob19.1 mm diam., 127 mm long steel rods12.7 mm x 12.7 mm x 12.7 mm alignment cube drilled with holes6.4 mm x 6.4 mm slotsspaced 16.5 mm on center w/ 6.4 mm x 6.4 mm (0.25” x 0.25”) gear rack 2018 by the American Association of State Highway and Tran
40、sportation Officials. All rights reserved. Duplication is a violation of applicable law.TS 2d TP 131-8 AASHTO 7. HAZARDS 7.1. This practice and associated standards involve handling of hot asphalt binder, aggregates and asphalt mixtures. It also includes the use of sawing and coring machinery and se
41、rvo-hydraulic testing equipment. Use standard safety precautions, equipment, and clothing when handling hot materials and operating machinery. 8. STANDARDIZATION 8.1. Items associated with this practice that require calibration are included in the documents referenced in Section 2.2. Refer to the pe
42、rtinent section of the referenced documents for information concerning calibration. 9. PROCEDURE 9.1. Test Specimen Fabrication 9.1.1. Testing shall be performed on 150 9 mm diameter by 38 to 50 mm thick test specimens fabricated in accordance with AASHTO PP 95, Preparation of Indirect Tension Perfo
43、rmance Test Specimens. 9.1.2. Prepare at least three test specimens to the target air void content and aging condition in accordance with AASHTO PP 95, Preparation of Indirect Tension Performance Test Specimens. Note 1A reasonable air void tolerance for test specimen fabrication is 0.5 %. 9.2. Test
44、Specimen Instrumentation 9.2.1. Attach the gauge points to the specimen with epoxy using the alignment device mentioned in Section 6.7. The recommended gauge length is 101.6 mm 1.0 mm measured center to center of the gauge points. The gauge length is centered on the intersection of the diametral lin
45、es drawn according to AASHTO PP XX-XX Preparation of Indirect Tension Performance Test Specimens, Section 10.7. Attach the gauge points on the horizontal and vertical lines. Repeat the process on the opposing cut face of the specimen. Allow the epoxy to harden according to manufacturers specificatio
46、ns. Note 2For open-graded asphalt mixtur es with large surface voids, prior to gluing the gauge points, examine the locations where gauge points would be placed before gluing to avoid large surface voids under the gauge points. Follow the instructions in Section 10.7.2 of AASHTO PP 95, Preparation o
47、f Indirect Tension Performance Test Specimens to avoid large surface voids under the gauge points. 9.2.2. Attach LVDT core rods and heads. 9.3. Alignment of Load Guide Deviceperformed when initially setting up the machine or when the difference of the horizontal or vertical LVDT strains on both face
48、s are greater than 20 microstrains. 9.3.1. Once the LGD has been placed in the chamber, the device needs to be aligned. To align the device, use a stiff specimen (Section 6.8) which has been instrumented according to Section 9.2. 9.3.2. Place the stiff specimen on its edge and align the vertical lin
49、e with center lines marked on the LGD. Apply a small seating load of 0.05 kN to hold the specimen while aligning. Check both 2018 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS 2d TP 131-9 AASHTO faces of the specimen for proper alignment. If the temperature chamber is small, the use of a mirror may assist in aligning the face opposite the operator. 9.3.3. Increase the load to 0.5 kN to secure the specimen in the current alig
