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61 70 SS-1h CRS-1 Trackless Interface Shear Strength (psi) 60 50 Clean/Dry 40 Dirty/Dry 30 20 10 0 0.031 0.062 0.155 0.031 0.062 0.155 0.031 0.062 0.155 Residual Application Rate (gal/yd2) (a) No-Confinement Condition 90 Interface Shear Strength (psi) SS-1h CRS-1 Trackless 80 70 60 50 clean/dry 40 dusty dry 30 20 10 0 0.031 0.062 0.155 0.031 0.062 0.155 0.031 0.062 0.155 Residual Application Rate (gal/yd2) (b) Confinement Condition Figure 64. Dust effect on ISS with (a) no-confinement and (b) confinement. 4.4.4Effect of Wet (Rainfall) Conditions 100% coverage. As shown in this figure, using 50% coverage of Tacked Surface significantly reduced the ISS by a factor ranging from 50% to 70%. Table 24 presents the statistical analysis of the effects of Table 25 presents the LTCQT test results for 50% cover- wet conditions on ISS based on a two-tailed t-test at a 95% age. The tensile strength test results were highly variable. This confidence level. As shown in this table, the majority of the may be due to the partial coverage of the tacked surfaces. For cases indicated that wet conditions had no significant effect actual pavements, this suggests inconsistent interface bond- on the measured ISS. Figure 65 presents the effects of water ing behavior for tacked surfaces with incomplete or non- (i.e., light rainfall) of a tacked surface at no confinement and uniform coverage. with confinement (20 psi) on ISS. It is noted that the major- ity of the cases showed no significant differences between dry and wet conditions. 4.5Experiment IV: Effects of Test Temperature and Its Relationship with Tack Coat Rheology 4.4.5 Effects of Tack Coat Coverage 4.5.1Interface Bond Strength As previously discussed, 50% tack coat coverage was only at Various Temperatures investigated for SS1-h. For the application of SS-1h, the residual application rate of 0.031 gal/yd2 was achieved with a Table 26 presents the ISS test results for trackless and high level of error (see Table 5); therefore, this residual appli- CRS-1 specimens. Each value represents the average of two cation rate was not considered in the analysis. On the other test specimens. At temperatures over 50C, some specimens hand, the residual application rates of 0.062 and 0.155 gal/ collapsed before shearing due to their own weights. This mostly yd2 at 50% coverage were comparable with the ones at 100% occurred at the low residual application rate and for the coverage. Figure 66 compares the measured ISS for 50 and CRS-1 emulsion. As shown in Table 26, the trackless material

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62 Table 24. Statistical analysis of the effects of wet conditions on ISS. Tack Statistical Test Rate Condition Confinement P-value Results Dry vs. Wet 0.031 Clean Unconfined 0.0743 Not Significant Dry vs. Wet 0.031 Clean Confined 0.2168 Not Significant Dry vs. Wet 0.031 Dusty Unconfined 1.0000 Not Significant Dry vs. Wet 0.031 Dusty Confined 0.8961 Not Significant Dry vs. Wet 0.062 Clean Unconfined 0.0147 Significant Dry vs. Wet 0.062 Dusty Confined 0.8444 Not Significant SS-1h Dry vs. Wet 0.062 Clean Unconfined 0.0132 Significant Dry vs. Wet 0.062 Dusty Confined 0.0108 Significant Dry vs. Wet 0.155 Clean Unconfined 0.9313 Not Significant Dry vs. Wet 0.155 Dusty Confined 0.1865 Not Significant Dry vs. Wet 0.155 Clean Unconfined 0.5511 Not Significant Dry vs. Wet 0.155 Dusty Confined 0.7320 Not Significant 50 No-confinement Confinement 45 Interface Shear Strength (psi) 40 35 30 Dry/Clean 25 Wet/Clean 20 15 10 5 0 0.031 0.062 0.155 0.031 0.062 0.155 2 Residual Application Rate (gal/yd ) (a) Clean Condition 60 Interface Shear Strength (psi) No-confinement Confinement 50 40 Dry/Dirty 30 Wet/Dirty 20 10 0 0.031 0.062 0.155 0.031 0.062 0.155 2 Residual Application Rate (gal/yd ) (b) Dusty Condition Figure 65. Effect of wetness on ISS for SS-1h tack coat with (a) clean and (b) dusty conditions.

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63 90 100% 80 50% Interface Shear Strength (psi) 70 60 50 40 30 20 10 0 0.062 0.155 Residual Application Rate (gsy) Figure 66. Effect of tack coat coverage on ISS. Table 25. LTCQT test results with 50% coverage surface. Residual Test Maximum Maximum Standard Tack Coat Temperature Tensile Load Average 1 Application Tensile Deviation COV (%) Material (PULT /SULT) Rate (C) (lb) Strength (psi) (PULT /SULT) 51.0 12.3 0.63 0.031 55.0 5.4 0.28 8.6/0.44 3.48/0.18 40.4 SS-1h 50% 57.0 8.1 0.41 52.0 14.3 0.73 0.155 51.0 9.1 0.46 12.3/0.62 2.78/0.14 23.0 53.0 13.4 0.68 1 All tack coats were tested at 53C. Table 26. ISS at various test temperatures. Mean ISS (psi) Trackless CRS-1 Temperature 0.031 0.062 0.031 0.062 0.155 (C) 0.155 gal/yd2 gal/yd2 gal/yd2 gal/yd2 gal/yd2 gal/yd2 10 132.0 255.7 370.4 147.6 196.8 331.7 0 127.1 263.1 401.9 111.7 171.3 216.3 10 88.5 194.1 322.7 85.4 91.1 120.4 20 39.7 101.8 167.5 46.0 46.3 45.5 30 21.9 45.8 75.3 11.0 16.8 21.5 40 3.8 17.8 34.1 2.9 1.9 3.2 50 * 4.4 14.2 * * 2.8 60 * 5.4 18.0 * * * *Specimens collapsed under their own weights before shear loading.

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64 450 -10C 0C -10C 0C 10C 20C 350 400 10C 20C 30C 40C 350 30C 40C 50C 60C 300 50C 300 250 ISS (psi) 250 200 200 ISS (psi) 150 150 100 100 50 50 0 0.000 0.050 0.100 0.150 0.200 0 0.000 0.050 0.100 0.150 0.200 Residual Application Rate (gsy) Residual Application Rate (gsy) (a) Trackless (b) CRS-1 Figure 67. Variation of the ISS with residual application rate and test temperature. had a greater shear resistance than CRS-1 at high tempera- It is also noted that, for CRS-1, the ISS did not consistently tures. It is noted that the PG binder used in the asphalt mix- increase with the increase in residual application rates at ture was PG 64-22; therefore, test temperatures ranging from a temperature of 20C or higher. On the other hand, ISS 0 to 60C did not exceed the associated PG-grading range. consistently increased with residual application rate for the Figure 67 (a and b) presents the variation of the ISS with trackless material, even at high test temperatures. residual application rates and test temperatures. For both Variation of the ISS with test temperatures at each residual tack coat materials, as the residual application rate increased, application rate is presented in Figure 68. As shown in this fig- the ISS increased at all temperatures, and the highest ISS val- ure, ISS of the trackless increases from 60C to 0C and then ues were measured at the rate of 0.155 gal/yd2; therefore, for decreases toward -10C. This is due to the low elongation the range of residual application rates from 0.031 to 0.155 properties of the trackless at low temperatures (see Table 16). gal/yd2, there was no optimum tack coat residual application In contrast, the ISS for CRS-1 continuously increased as tem- rate as might have been expected. This may be attributed to perature decreased. However, the trackless material still pro- the highly oxidized and coarse HMA surface at the selected duced higher shear strengths than CRS-1 at low temperatures site, which required greater tack coat rates than expected. and at residual application rates of 0.062 and 0.155 gal/yd2. 160 300 450 Trackless 140 Trackless Trackless 400 250 Interface Shear Strength (psi) Interface Shear Strength (psi) CRS-1 CRS-1 CRS-1 Interface Shear Strength (psi) 350 120 200 300 100 250 80 150 200 60 100 150 40 100 50 20 50 0 0 0 -10 0 10 20 30 40 -10 0 10 20 30 40 50 60 -10 0 10 20 30 40 50 60 Temperature (C) Temperature (C) Temperature (C) (a) 0.031 gal/yd2 (b) 0.062 gal/yd2 (c) 0.155 gal/yd2 Figure 68. Variation of the ISS with test temperature.