Long-Term Field Performance of Warm Mix Asphalt Technologies (2017) / Chapter Skim
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31 Introduction This chapter focuses on wheel-path longitudinal cracking that is fatigue-related. Figures 4.1 (a)
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32 Figure 4.7 plots the wheel-path longitudinal crack length versus pavement age for the second-round distress survey. As shown, although some longitudinal cracks start to develop when the pavements are 3 years old, more longitudinal cracking is seen in pavements that are 6 years old or older.
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33 0 50 100 150 200 250 300 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 W he el -p at h Lo ng itu di na l C ra ck L en gt h, ft /2 00 ft Pavement Age, years HMA WMA Figure 4.3. Wheel-path longitudinal crack length versus pavement age for the first-round distress survey.
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34 (a) Comparison Between Chemical and Organic 1 6 0 0 2 4 6 8 10 N o.
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35 0 50 100 150 200 250 300 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 Se co nd -R ou nd W he el -P at h Lo ng it ud in al C ra ck L en gt h, ft /2 00 ft Pavement Age, years HMA WMA Figure 4.7. Wheel-path longitudinal crack length versus pavement age for the second-round distress survey.
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36 Paired Ranking Analysis for Wheel-Path Longitudinal Cracking The material properties obtained from the field cores and extracted binders were used to determine potential significant determinants for wheel-path longitudinal cracking using paired ranking analysis. These material properties include the following: 1.
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37 Statistical Predictive Models for Wheel-Path Longitudinal Cracking The PLS method was applied to develop a predictive wheelpath longitudinal cracking model. The following factors were considered for the model based on literature findings: • Mixture properties: IDT strength at 68°F; fracture work density at 68°F; mixture fracture energy at 68°F; dynamic modulus at 70°F and 1 Hz; in-place air voids; aggregate passing #4, #8, #200 sieve; and NMAS.
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38 development. Five parameters were selected: total pavement thickness (+)
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39 This model gives a R2 of 0.85, a standard error of the estimate of 0.59, and Mallow's Cp of 6.0, indicating good prediction quality. Figure 4.12 (b)
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40 than 50 percent probability for crack initiation, which is reasonable. To validate the model, the LOOCV method was used.
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