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OCR for page 60
60 1.8 1.8 CRS-1 CRS-1 1.6 1.6 SS-1h ISSconfined/ISSno-confined SS-1h ISSconfined/ISSno-confined 1.4 1.4 Trackless Trackless 1.2 1.2 1 1 0.8 0.8 0.6 0.6 0.4 0.4 0.2 0.2 0 0 0.031 0.062 0.155 0.031 0.062 0.155 2 Residual Application Rate (gal/yd ) Residual Application Rate (gal/yd2) (a) Clean and Dry Conditions (b) Dusty and Dry Conditions Figure 63. Ratio of ISS with confinement to no confinement. derived from the tack coat material. The effect of confinement had a significant effect on the measured ISS. Figure 64 pre- was more pronounced under dusty and dry conditions. sents the effects of dust on the ISS values at no confinement and confinement (20 psi) test conditions. As shown in Fig- ure 64, the majority of the cases showed differences between 4.4.3Effect of Dusty Conditions clean and dusty conditions. In general, dusty conditions exhib- of HMA Surface ited higher interface strength than clean conditions, especially Table 23 presents the statistical analysis of the effects of when tested with a confinement condition. One possible dusty conditions on ISS based on a two-tailed t-test at a 95% explanation for these results is that a high-viscosity, gritty confidence level. As shown in this table, results were mixed, mastic was formed when tack coat combined with dust and, with 13 out of the 24 cases indicating that dusty conditions thus, provided a greater resistance to shear movement. Table 23. Statistical analysis of the effects of dusty conditions on ISS. Tack Statistical Test Rate Condition Confinement P-value Results Clean vs. Dusty 0.031 Dry Unconfined 0.1036 Not Significant Clean vs. Dusty 0.031 Dry Confined 0.0806 Not Significant Clean vs. Dusty 0.031 Wet Unconfined 0.6903 Not Significant Clean vs. Dusty 0.031 Wet Confined 0.0274 Significant Clean vs. Dusty 0.062 Dry Unconfined 0.0188 Significant Clean vs. Dusty 0.062 Dry Confined 0.0264 Significant SS-1h Clean vs. Dusty 0.062 Wet Unconfined 0.0046 Significant Clean vs. Dusty 0.062 Wet Confined 0.4097 Not Significant Clean vs. Dusty 0.155 Dry Unconfined 0.2339 Not Significant Clean vs. Dusty 0.155 Dry Confined 0.1744 Not Significant Clean vs. Dusty 0.155 Wet Unconfined 0.1234 Not Significant Clean vs. Dusty 0.155 Wet Confined 0.0165 Significant Clean vs. Dusty 0.031 Dry Unconfined 0.1078 Not Significant Clean vs. Dusty 0.031 Dry Confined 0.0462 Significant Clean vs. Dusty 0.062 Dry Unconfined 0.6699 Not Significant CRS-1 Clean vs. Dusty 0.062 Dry Confined 0.0048 Significant Clean vs. Dusty 0.155 Dry Unconfined 0.0078 Significant Clean vs. Dusty 0.155 Dry Confined 0.0039 Significant Clean vs. Dusty 0.031 Dry Unconfined 0.0044 Significant Clean vs. Dusty 0.031 Dry Confined 0.0369 Significant Clean vs. Dusty 0.062 Dry Unconfined 0.0055 Significant Trackless Clean vs. Dusty 0.062 Dry Confined 0.0007 Significant Clean vs. Dusty 0.155 Dry Unconfined 0.9063 Not Significant Clean vs. Dusty 0.155 Dry Confined 0.0640 Not Significant