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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 60C. SS-1h, CRS-1, and ing point. Two replicates of each test were conducted. As PG 64-22 had a TOPT of 54, 43, 42C, 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 C (poises)a 1.E+06 Rotational Viscosity at 135 C (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 C (10 mm) 70 100 Softening Point (C) 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.