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NCHRP Report 712: Optimization of Tack Coat for HMA Placement (2012)
National Cooperative Highway Research Program (NCHRP)

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Button, Joe, Elseifi, Mostafa A, Scherocman, James A, Mohammad, Louay N, Bae, Abraham, Patel, Nachiketa, Transportation Research Board. "4.3 Experiment II: Rheological Properties of Tack Coat Materials and Its Relationship to Bond Strength." NCHRP Report 712: Optimization of Tack Coat for HMA Placement. Washington, DC: The National Academies Press, 2012.

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Page
51
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Page
51
Front Matter (R1-R11)
Summary (1-3)
1.3 Research Scope (4-4)
1.4 Research Approach (5-6)
2.1 Tack Coat Materials (7-7)
2.3 Tack Coat Breaking and Setting Time (8-8)
2.4.1 Equipment (9-9)
2.4.2 Proper Tack Coat Application (10-10)
2.5.1 Laboratory Characterization of Tack Coats (11-13)
2.6 Worldwide Survey (14-18)
3.2.1 HMA Pavement Surface Preparation (19-19)
3.2.3 Tack Coat Application (20-21)
3.2.4 Overlay Construction (22-23)
3.2.6 Specimen Coring and Conditioning (24-26)
3.3 Experiment Plan I: Development of a Test Device to Evaluate the Quality of the Bond Strength of Tack Coat Spray Application in the Field (27-27)
3.6 Experiment Plan IV: Effects of Test Temperature and Its Relationship with Tack Coat Rheology (28-29)
3.8 Experiment Plan VI: Effects of Surface Texture and Permeability on Interface Shear Strength (30-31)
3.9 Theoretical Investigation (32-34)
4.1.2 Types of Tack Coat Applied to Different Pavement Surfaces (35-36)
4.1.3 Findings Related to Tack Coat Application Methods (37-43)
4.1.4 Findings Related to Tack Coat Application (44-44)
4.2 Experiment I: Development of a Test Device to Evaluate the Quality of the Bond Strength of Tack Coat Spray Application in the Field (45-45)
4.2.2 Second Generation of LTCQT (46-47)
4.2.3 Development of Tack Coat Test Procedure Using LTCQT (48-48)
4.2.5 Effect of Tack Coat Temperature on the Ultimate Tensile Strength (49-50)
4.3 Experiment II: Rheological Properties of Tack Coat Materials and Its Relationship to Bond Strength (51-51)
4.3.2 Relationship Between LTCQT Test Results and Tack Coat Rheological Properties (52-52)
4.4 Experiment III: Development of a Laboratory Test Procedure to Measure the Interface Bond Strength (53-54)
4.4.1 Effects of Tack Coat Characteristics on Interface Shear Strength (55-57)
4.4.2 Effect of Confining Pressure (58-59)
4.4.3 Effect of Dusty Conditions of HMA Surface (60-60)
4.5.1 Interface Bond Strength at Various Temperatures (61-64)
4.5.3 Relationship Between Interface Shear Strength and Tack Coat Rheology (65-65)
4.6.1 Effects of Tack Coat Type and Residual Application Rate (66-67)
4.6.3 Effects of Surface Wetness (68-68)
4.7 Experimental VI: Effects of Texture and Permeability on Tack Coat Bond Strength (69-71)
4.8 Theoretical Investigation (72-79)
Section 5 - Conclusions (80-81)
References (82-83)
Appendix A - Worldwide Survey Questionnaire (84-88)
Appendix B - ATacker Displacement Rate Verification Experiment (89-89)
Appendix C - Standard Test Method for Assessing Tack Coat Installation Quality Using the LTCQT (90-96)
Appendix D - Comparison of the LISST Device and the Simple Shear Tester (97-97)
Appendix E - Standard Test Procedure for Measuring Interface Bond Strength in the Laboratory Using the LISST (98-105)
Appendix F - Tack Coat Training Manual (106-134)
Abbreviations used without definitions in TRB publications (135-135)

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51 Table 15. Maximum tensile strength and optimum temperature. Trackless SS-1h PG 64-22 CRS-1 Maximum Tensile Strength (psi) 1.84 2.51 4.34 1.84 Optimum Temperature (°C) 60 52 43 42 a lower drop in the tensile strength from the peak value as 4.3Experiment II: Rheological the temperature increased. Furthermore, trackless emulsion Properties of Tack Coat maintained its tensile strength in the post peak region with Materials and Its Relationship the increase in temperature. Results shown in Figure 54 indi- to Bond Strength cate that each tack coat material exhibits its maximum ten- sile strength at a distinct temperature. This temperature was Four consistency tests were conducted on PG 64-22 binder referred to as the optimum temperature, TOPT. At a tempera- and the residuals of SS-1h, CRS-1, and trackless emulsions ture higher or lower than TOPT, the tensile strength normally (see Figure 55). The residual asphalts were obtained accord- decreased. To determine the peak tensile strength (SMAX) and ing to ASTM D 244, Residue by Evaporation. Trackless, SS-1h, the optimum temperature (TOPT), polynomial regression and CRS-1 are emulsified asphalts with residual percentages lines were fitted for each tack coat. The peak strength from of 55.3%, 63.0%, and 58.2%, respectively. On the other hand, the trend lines was then set to SMAX, and the temperature cor- PG 64-22 has 100% residual. The tests performed were pen- responding to SMAX was set to TOPT. Trackless material had the etration, absolute viscosity, rotational viscosity, and soften- highest optimum temperature of 60°C. SS-1h, CRS-1, and ing point. Two replicates of each test were conducted. As PG 64-22 had a TOPT of 54, 43, 42°C, respectively. PG 64-22 shown in Figure 55a, trackless material was the hardest fol- material showed the highest maximum tensile strength of 4.3 lowed by SS-1h, PG 64-22, and CRS-1. Ranking of viscosity psi. Table 15 summarizes the measured TOPT and SMAX for the of the materials from this test was consistent with the results four tack coat materials evaluated. of the penetration test (see Figure 55b). In addition, trackless 3.0 Absolute Viscosity at 60 ºC (poises)a 1.E+06 Rotational Viscosity at 135 ºC (Pa-s) 2.5 1.E+05 2.0 1.E+04 1.5 1.E+03 1.0 1.E+02 0.5 1.E+01 1.E+00 0.0 Trackless SS-1h PG 64-22 CRS-1 Trackless SS-1h PG 64-22 CRS-1 (b) Absolute viscosity test (a) Penetration test 120 80 Penetration at 25 ºC (10 mm) 70 100 Softening Point (ºC) a 60 -1 80 50 60 40 30 40 20 20 10 0 0 Trackless SS-1h P G 64-22 CRS-1 Trackless SS-1h PG 64-22 CRS-1 (c) Rotational viscosity test (d) Softening point test Figure 55. Rheological test results of tack coat materials.