1、Standard Method of Test for Evaluation of the Low-Temperature Tensile Property of Hot-Poured Asphalt Crack Sealant by Direct Tension Test AASHTO Designation: T 369-171Technical Section: 4e, Joints, Bearings, and Geosynthetics Release: Group 2 (June 2017) American Association of State Highway and Tra
2、nsportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D.C. 20001 TS-4e T 369-1 AASHTO Standard Method of Test for Evaluation of the Low-Temperature Tensile Property of Hot-Poured Asphalt Crack Sealant by Direct Tension Test AASHTO Designation: T 369-171Technical Section: 4e, Joi
3、nts, Bearings, and Geosynthetics Release: Group 2 (June 2017) 1. SCOPE 1.1. This test method applies to hot-poured asphalt crack sealant used in the construction and maintenance of roadways as specified in MP 25 and PP 85. 1.2. The test method is used to determine the extendibility and strain energy
4、 density (SED) of sealants at low temperature. It can be used with unaged material or with material aged according to T 367. The test apparatus is designed for testing within the temperature range from 4 to 40C. 1.3. This standard covers the determination of extendibility and percent modulus decay i
5、n hot-poured asphalt crack sealant with the use of direct tension testing and by applying the tensile stressstrain test. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: M 320, Performance-Graded Asphalt Binder MP 25, Performance-Graded Hot-Poured Asphalt Crack Sealant PP 85, Grading or Verifying the
6、Sealant Grade (SG) of a Hot-Poured Asphalt Crack Sealant T 314, Determining the Fracture Properties of Asphalt Binder in Direct Tension (DT) T 367, Accelerated Aging of Hot-Poured Asphalt Crack Sealant Using a Vacuum Oven 2.2. ASTM Standards: D5167, Standard Practice for Melting of Hot-Applied Joint
7、 and Crack Sealant and Filler for Evaluation E1, Standard Specification for ASTM Liquid-in-Glass Thermometers E77, Standard Test Method for Inspection and Verification of Thermometers 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is
8、a violation of applicable law.TS-4e T 369-2 AASHTO 3. TERMINOLOGY 3.1. Definitions: 3.1.1. hot-poured asphalt crack sealanthot-poured modified asphaltic material used in pavement cracks and joints. Note 1Based on the references, hot-poured asphalt crack sealant is typically applied at a temperature
9、of 160C or above. 3.1.2. effective gauge lengthelongation of a standard dog boneshaped test specimen due to an applied axial load P is equivalent to that of a simple rectangular specimen with the same cross-sectional dimensions of the restricted section. Effective gauge length, Le, is defined as the
10、 length of the simple rectangular specimen and has been determined to be 20.3 mm. 3.1.3. tensile stresstensile load divided by the true area of a cross section of the specimen. 3.1.4. tensile strainchange in the effective gauge length by the application of tensile load divided by the original unload
11、ed effective gauge length. 3.1.5. brittle materialthe stressstrain curve is linear up to fracture at about 1 to 2 percent elongation. 3.1.6. brittle-ductile materialthe stressstrain curve is curvilinear and the stress is gradually reduced after the peak point. The failure happens by gradually breaki
12、ng the molecular bond within the material. 3.1.7. ductile materialthe material does not rupture in the direct tension test but elongates due to high strain. 3.1.8. rubbery behaviormaterials that exhibit rubbery behavior can be stretched to extreme elongation without rupture. 3.1.9. percent modulus d
13、ecaythe percentage modulus deduction after 10 s of loading. 4. SUMMARY OF PRACTICE 4.1. This practice contains the procedure to measure the extendibility and the strain energy density of a hot-poured asphalt crack sealant using a direct tension test (DTT). The material is bonded between two end tabs
14、 made of poly(methyl methacrylate) (PMMA) and subjected to a constant strain rate at a specific temperature. 4.2. The test method is developed to select a hot-poured asphalt crack sealant at temperatures where it exhibits rubbery behavior. 4.3. A linear variable differential transformer (LVDT) is us
15、ed to measure the elongation of the test specimen as it is pulled in tension at a constant strain rate of 6 percent/min (1.2 mm/min). A load cell is used to monitor the load during the test. The stress and strain at the point of rupture or peak load are reported. 5. SIGNIFICANCE AND USE 5.1. This te
16、st is intended for hot-poured asphalt crack sealant applied to roadway joints and cracks. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 369-3 AASHTO 5.2. The test temperature is determined to
17、be the lowest temperature experienced by the pavement surface in the geographical area for which the sealant is intended. 5.3. The sealant extendibility is a parameter of the capacity of the sealant to sustain large deformations due to crack expansion at low temperature without fracture. 5.4. The pe
18、rcent modulus decay is an indication of how fast the sealant can release the imposed loading. A higher percentage decay shows that the sealant can relax the load faster. 5.5. This method is intended for aged sealants, which could become stiffer or softer with age. 6. APPARATUS 6.1. Direct Tension Te
19、st (DTT) DeviceThe DTT system consists of two metal grips to hold the specimen, an environment chamber, a loading device, and a control and data acquisition system. The instrument must meet the requirements stated in T 314. 6.2. Specimen End Tabs and Gripping SystemEnd tabs made from PMMA having dim
20、ensions as described in Figure 1 that shall be bonded to both ends of the test specimen to transfer the tensile load to the sealant. The manufacturing requirements of the end tabs and the gripping system shall meet the requirement in T 314. 6.3. Test ChamberA calibrated circulated temperature contro
21、l system shall have a temperature range from 4 to 40C. The insulated test chamber shall be capable of maintaining a temperature of 0.1C. 6.4. Specimen MoldsThe specimen molds should be made from aluminum. Molds shall have dimensions as specified in Figure 1. A silicon-based release agent, as describ
22、ed in Section 7.2, shall be used to prevent the sealant from adhering to the aluminum molds. 6.5. Laboratory OvensTwo forced-air convection ovens capable of producing, reaching, and maintaining a temperature of 200 0.5C for heating the sealant and molds. 6.6. Calibrated ThermometerA calibrated liqui
23、d-in-glass thermometer of suitable range with subdivisions of 0.1C is required for verification of the temperature transducer. This thermometer shall be a partial immersion thermometer with an ice point and calibrated in accordance with ASTM E77. An ASTM 133C thermometer is suitable. 2017 by the Ame
24、rican Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 369-4 AASHTO Note: Dimensions are in mm. Figure 1Dimensions for DTT, End Insert, and Mold 7. REAGENTS AND MATERIALS 7.1. Fluid for Test ChamberA fluid that is no
25、t absorbed by or does not affect the properties of the crack sealant being tested. The bath fluid shall be optically clear at the test temperature. Ethyl alcohol is suggested to use as a fluid for temperature control. The aqueous mixture of potassium Dia.15.0025.0038.0050.0020.0227.003.00 5.007.0044
26、.00100.0424.00100.0054.001.6012.00B6.00100.003.93R 7.5044.6524.00Dia. 10.00100.0062.0038.00 24.003.00Mold BaseMold HalfEnd Insert16.50 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 369-5 AASHT
27、O acetate and deionized water used in T 314 has been found to form a turbid solution at a temperature of 40C. 7.2. Release AgentA proper release agent to prevent the crack sealant from sticking to the mold. A silicon-based release agent is recommended. 7.3. SolventA solvent can properly clean the mo
28、lds, end tabs, and plates. The parts cleaned by the solvent shall be submerged in the ethyl alcohol prior to use. This ensures the proper bond between sealant and end tabs. 7.4. Cleaning ClothsCloths for wiping molds, end tabs, and plates. 8. HAZARDS 8.1. Standard laboratory caution should be used i
29、n handling hot sealant in accordance to ASTM D5167, and required safety procedures should be followed when chemical agents are used. 9. VERIFICATION AND CALIBRATION 9.1. DTTFollow the procedure as stated in T 314. 9.2. Test ChamberVerify the calibrated temperature transducer with the calibrated ther
30、mometer in Section 6.6. 10. SAMPLES PREPARATION 10.1. All hot-poured asphalt crack sealant to be tested must undergo the accelerated aging process according to T 367. It is recommended that a minimum of 35 g of hot-poured asphalt crack sealant be prepared and undergo accelerated aging for a set of t
31、ests. 10.2. Anneal the sealant from which the test specimen is obtained by heating for 30 min. After 15 min, place the sealant in the oven, remove the sealant from the oven shortly, and stir the sealant by spatula to prevent segregation. 10.3. Follow the procedure in Sections 10.1 to 10.7.5 of T 314
32、 with the following modifications: Note 2If a spray-type silicon-based release agent is used, start from one side of the mold and slowly move toward the other side. Only one spray should be applied to the mold. Note 3Place the molds and end tab assembly on top of a ceramic tile heated to 50C lower t
33、han the sealant pouring temperature. The ceramic tile should be placed in the preheated oven for 15 min. 11. CONDITIONING 11.1. Follow the procedure as stated in T 314. 12. PROCEDURE 12.1. Bring the DTT chamber to the test temperature. (See Note 4). Note 4Select test temperatures in accordance with
34、the applicable material specification (e.g., MP 25 or M 320). 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 369-6 AASHTO 12.2. Prepare four test specimens according to Section 10. 12.3. Follow
35、 the procedure in Sections 12.2 to 12.3 of T 314 with the following modifications: Note 5Adjust the load frame to allow 20-mm traveling distance; then place the specimen on the loading pin. Remove the slack between the specimen and the loading pins. Note 6Manually adjust the thumb wheel on the contr
36、ol box to apply tension in the specimen until a load of 1 0.5 N is shown on the screen. Then calibrate the stroke and load back to zero. 12.4. Set the strain rate to 6 percent/min (1.2 mm/min) and start the test. 12.5. After the specimen fractures, degradation is observed, or maximum traveling dista
37、nce is reached (whichever comes first), stop the test and remove the specimen from the loading frame. 12.6. The extendibility is identified as follows: 12.6.1. When the specimen fractures (breaks into two pieces), the extendibility is easily identified as the strain at peak load (maximum stress). 12
38、.6.2. When the specimen does not fracture, but reaches a maximum stress and then flows without fracture, the extendibility is recorded as the strain corresponding to the maximum stress. 12.6.3. When the specimen does not fracture or load reduction is not observed, the extendibility is recorded as th
39、e strain at the end of the traveling distance. 12.7. Repeat steps in Sections 12.3 to 12.6 for the remaining three specimens. 12.8. After testing is complete, discard the asphalt portions of the spent specimens and clean the end tabs by soaking them in solvent and wiping with a soft cloth. After wip
40、ing the end tabs, use a detergent soap solution to remove any oil film residue left by the cleaner material. Alternatively, use a degreasing spray cleaner. Clean the end tabs thoroughly. A grease film on the sealant bonding area can create a weak bond causing bond failures. 13. CALCULATIONS 13.1. Fo
41、r each test result, calculate the engineering stressstrain: 0ffPA=(1) ffeLL= (2) where: f= peak stress (Pa); Pf= measured load at peak (N); A0= original cross-sectional area (= 0.00018 m2); f= measured strain at peak load; Lf= measured elongation at failure (L) (mm); and Le= effective gauge length (
42、= 0.020.3 m). 13.2. For each test result, calculate the true stressstrain: 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 369-7 AASHTO 0fLL=(3) ( )0tfiPPeAA= =(4) where: = true strain; Lf= meas
43、ured elongation at failure (L) (mm); L0= effective gauge length (= 0.0203 m); = true stress (Pa); Pf= measured load at peak (N); Ai =current cross-sectional area (m2); e = Eulers number, the base of the natural logarithm; = strain rate (1/s); t = time (s); and A0= original cross-sectional area (= 0.
44、000018 m2). 13.3. The extendibility is identified as . 13.4. Select the three test results that give the best coefficient of variation of the extendibility. Calculate the mean and standard deviation for SED from the selected three test results. 13.5. Calculate the percent modulus decay: 13.5.1. From
45、 the Boltzmann superposition principle, the stressstrain relationship for a viscoelastic material can be expressed using a convolution integral as follows: ( ) ( )( )0tdtt E t t dtdt= (5) where: t = time (s); t = previous time interval (s); (t) = stress history (Pa); E(t) = the relaxation modulus (P
46、a); (t) = strain history; and ( )dtdt= time derivative of strain history. 13.5.2. The Prony series (generalized Kelvin model) is used to describe the viscoelastic behavior of hot-poured crack sealants as presented in Equation 6. ( ) ( )/011iKtiiEt E E e=(6) where: E(t) = the relaxation modulus at ti
47、me t; E0= original material constant; Ei= material constants; e = Eulers number, the base of the natural logarithm; and i= retardation times. 2017 by the American Association of State Highway and Transportation Officials. All rights reserved. Duplication is a violation of applicable law.TS-4e T 369-
48、8 AASHTO 13.5.3. Substituting Equation 6 into Equation 5, the expression of the stress becomes: ( ) ( )( )( )001itttNiidtt E t E e dtdt= (7) 13.5.4. In the DTT, the sealant is subjected to a constant strain rate beginning at time zero, ( )0 for 0 for 0tttt=, with as the strain rate. The above convol
49、ution integral can then be solved as follows: ( ) ( )01itNiiit E t ER t e = (8) 13.5.5. The equation is used to fit the experimental data by means of the nonlinear least squares (NLS) technique to obtain the material constants E0, Ei, and i. 13.6. The percent modulus reduction after 10 s of loading is calculated as follows: ( ) ( )( )1010 01000EEME= (9) 14. REPORT 14.1. Report the following informa
