Relationships Between the Fatigue Properties of Asphalt Binders and the Fatigue Performance of Asphalt Mixtures (2022) / Chapter Skim
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6 Background Fatigue in Asphalt Pavements Traffic-associated fatigue damage is one of the major distresses in which flexible pavements fail. This type of distress is the result of many thousands -- or even millions -- of wheel loads passing over a pavement.
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Background 7 heavier the axle loads on a pavement and the higher the number of heavy vehicles, the more quickly fatigue cracking will occur, all else being equal. The pavement structure is also extremely important.
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8 Relationships Between the Fatigue Properties of Asphalt Binders and the Fatigue Performance of Asphalt Mixtures in the overlying structure, which in turn will reduce the fatigue life of the pavement system. Pavement drainage and moisture damage are also related to the subgrade.
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Background 9 Previous Research Related to Asphalt Binder Fatigue Performance Asphalt Binders' Effect on the Fatigue Performance of Asphalt Mixtures The recently developed AASHTO mechanistic-empirical design guide (ARA Inc., 2004) for flexible pavements uses the following equation for estimating cycles to failure for bottom-up traffic-associated fatigue cracking, calibrated for general use in the United States: = β ε 0.00432 1 1 (1)
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10 Relationships Between the Fatigue Properties of Asphalt Binders and the Fatigue Performance of Asphalt Mixtures widely used in the United States to characterize asphalt binders but was commonly used until the 1990s. The PI is considered to indicate the rheologic type of an asphalt binder, which is related to the shape of the modulus versus time function for the binder as well as its chemistry.
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Background 11 (Ahearn, 2015; Marks, 2015; Reinke et al., 2015)
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12 Relationships Between the Fatigue Properties of Asphalt Binders and the Fatigue Performance of Asphalt Mixtures numerous studies. Specifically, when ΔTc becomes too negative, a failure through nonloadassociated cracking is more likely to occur.
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Background 13 strongly to the binder phase angle than to the storage modulus, with healing increasing with increasing phase angles above about 35 degrees. At lower phase angles, there appears to be little or no healing.
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14 Relationships Between the Fatigue Properties of Asphalt Binders and the Fatigue Performance of Asphalt Mixtures Problems with the Existing Binder Fatigue Specification Test Before the results of NCHRP 09-59 can be discussed, perceived shortcomings in the current approach to ensuring adequate fatigue performance must be understood. The existing specification was developed during SHRP and was largely based on the observation that a dramatic increase in fatigue cracking was observed when the estimated loss modulus of the binder exceeded a value of about 3 Megapascal (MPa)
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Background 15 An additional potential problem in the current binder specification was discussed previously in connection with low-temperature cracking -- physical hardening can cause significant errors in BBR test data. Such errors will in general result in a binder grade lower than it should be, increasing the potential for transverse cracking.
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16 Relationships Between the Fatigue Properties of Asphalt Binders and the Fatigue Performance of Asphalt Mixtures the resulting ranking of the candidate tests based on these criteria and their weights. It should be emphasized that the rating in Table 2 was not meant to be the only means for selecting the final tests, including for evaluation in the laboratory testing phase of NCHRP 09-59.
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Background 17 of mixtures. However, testing plans were modified early in the project and additional overly testing was abandoned.
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18 Relationships Between the Fatigue Properties of Asphalt Binders and the Fatigue Performance of Asphalt Mixtures The primary experiment in NCHRP 09-59 involved performing mixture fatigue tests -- both uniaxial and flexural -- and relating these results to the results of the selected binder tests to determine which showed the best correlation. This comparison was made by calculating the fatigue/fracture performance ratio (FFPR)
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