Rheological Characterization On Paving Performance Of Asphalt Binder

The durability of asphalt pavement directly impacts the service level of the road engineering infrastructure. With the deterioration of pavement distresses(rutting, cracking et al.), the driving comfort and safety is significantly decreased. In order to analyze and capture the mechanism of the distress development, damage and failure characteristics of pavement materials is always the most concerned topic in asphalt pavement field and, thus, so many focuses have been taken on the rutting and cracking resistance of asphalt concrete since it is the main paving material.Compared with looking at macroscopical concrete scale, overseas researchers have started to work on the smaller scale levels(asphalt binder, asphalt mastic et al.) and found the asphalt binder, which exists as the binder material in pavement, has different contribution degrees to the paving performance within different temperature ranges and good performance relationships between asphalt binder and asphalt concrete could be obtained. For lack of the effective laboratory testing methods and indicators for paving performance of asphalt binder, currently this set of evaluation is still mainly relied on empirical approach in China, which is adverse to the material purchase and quality control in practice.The objective of this work is to establish a rapidly efficient evaluation and analysis framework for core paving performance of asphalt binder using a dynamic shear rheometer(DSR). The asphalt binder performance were characterized in terms of systematically investigating the high temperature rutting potential, intermediate fatigue damage as well as the low temperature thermal cracking resistance. The asphalt aging effect was also covered for above paving performance study. Part of the research findings could be directly applied on both laboratory research and purchase of asphalt binders in practice for durability guarantee of asphalt concrete and pavements. The main findings of this dissertation are summarized as below.The high temperature deformation potential of asphalt binders were evaluated employing the repeated creep recovery(RCR) testing procedure. The non-recoverable viscoplastic strain response in RCR test was modeled and simulated using the strain hardening viscoplastic model. Based on the "Internal Characteristic Time" theory of viscoelastic materials, applying the time-temperature-stress superposition could successfully remove the temperature and stress effect on the creep compliance response of asphalt binder in the static creep test and thus, temperature-stress mastercurve of creep compliance was generated.In this dissertation work, a comprehensive research was conducted on characterizing fatigue failure behavior of asphalt binder at intermediate temperature range employing the accelerated fatigue test. Based on the pseudo strain energy approach, a new failure definition of maximum stored pseudo strain energy was proposed for defining the failure occurrence during the accelerated fatigue test, which is also consistent with failure identification in traditional time sweep fatigue test. A new unified fatigue failure criterion was developed upon the new failure definition and pseudo strain energy releasing rate parameter. This new failure criterion is independent on testing methods and loading modes so thus, exists as the material fundamental fatigue failure characteristics. The current fatigue model of asphalt binder was modified and improved based on this new failure criterion. The predictive binder fatigue life using this improved method was able to provide good correlation with the measured time sweep fatigue life in the lab and the predictive accuracy was significantly improved. Also, the field fatigue performance data from accelerated loading facility pavement was generally verified by means of this improved asphalt fatigue model.Aging and temperature both affect the asphalt fatigue performance. Within certain degree aging levels, the fatigue resistance of binder was decreased with aging, whereas this effect was observed to be opposite when the binder underwent a extreme long-term aging. Also, the asphalt fatigue resistance became better with increasing temperature, and the temperature shift factor determined from the linear viscoelastic range was able to remove the temperature effect on the damage characteristic curve. Unlike the asphalt mixture behavior, the failure criterion of asphalt binder also showed obvious temperature dependency. However, the linear viscoelastic temperature shift factor could also basically eliminate the temperature effect but, the predictive fatigue life resulted from the time-temperature superposition still exhibited larger error especially for some modified binders due to the fact that higher accuracy is required for the failure criterion equation fitting when applying the improved fatigue model of asphalt binder.The low temperature thermal cracking performance of asphalt binders were evaluated using the new developed 4 mm parallel plates geometry on a dynamic shear rheometer(DSR). The machine compliance correction was conducted for dynamic test data. Based on the interrelationship between the linear viscoelastic functions, relaxation modulus mastercurve of asphalt binder was converted from the elastic(storage) modulus mastercurve obtained from the dynamic tests. Employing the relaxation modulus and relaxation rate at 60 s as the evaluation indicators, aging was found to be significantly negative to the thermal cracking resistance whereas modification could generally improve the low temperature performance of asphalt binders.