Liyan Shan

Application of Thixotropy to Analyze Fatigue and Healing Characteristics of Asphalt Binder

The fatigue performance of asphalt binder is critical to understanding the fatigue performance of asphalt mixtures, especially the effects of healing. Although research into the fatigue and healing characteristics of asphalt binder is found in numerous references, an efficient technique to evaluate these characteristics still does not exist. Thixotropy is a concept that may help explain the material behavior and provide an efficient evaluation technique. This property is related to the breakdown and buildup of microstructure that may cause the changes observed during fatigue and healing tests. Thus, tracking the thixotropy of asphalt binders may be a good method to study fatigue and healing. For this study, experiments were performed to characterize the fatigue and healing characteristics of three typical asphalt binders. Then a common thixotropic model was characterized with a relatively simple stepped-flow test and oscillation experiment. The resulting model shows good correlation with the measured fatigue and healing tests. This finding, though based on a limited number of binders, suggests that thixotropy may play a role in the fatigue and healing characteristics of asphalt binder.

Separation of thixotropy from fatigue process of asphalt binder

The fatigue performance of asphalt binder is critical to understanding the fatigue performance of asphalt mixtures. For the fatigue process to be modeled properly, the mechanism responsible for the fatigue behavior must be understood properly. In asphalt binder, it is widely accepted that the fatigue process is related to damage. However, some researchers have used the concept of thixotropy to describe the fatigue process in binder with equal success. If the real mechanism responsible for the observed reduction in modulus during a fatigue test is not properly understood, misinterpretation may occur. Such misinterpretation may lead to an improper assessment of a given materials quality and the acceptance of bad or rejection of good materials. This study attempted to separate the influence of thixotropy from other mechanisms during a fatigue experiment Tests were performed to characterize the exponential thixotropy model of four typical asphalt binders. The relationships between dynamic modulus and phase angle in a fatigue test and in a healing test were compared to determine the thixotropy-influence phase. According to the thixotropy model and fatigue test results, thixotropy is separated from the damage process for the entire fatigue test. A value of 50% |G*| after separation is put forward to evaluate the true fatigue characteristics of asphalt binder. The findings from this study, although based on a limited number of binders, suggest that thixotropy plays an important role in the fatigue characteristics of asphalt binder. The findings also provide a reasonable failure criterion for defining a fatigue evaluation index.

Analysis of Linear Viscoelastic Response Function Model for Asphalt Binders

AbstractAsphalt binder properties play a significant role in the performance of asphalt pavement, but it is impossible to test the properties of asphalt binders under every condition. However, a suitable model that can be established using only a few tests can predict the behavior of asphalt binders under different conditions. Such models have received much attention over the last few decades. Many types of models are available, but most of them focus on only one kind of viscoelastic characteristic, whereas a good model should describe not only the dynamic viscoelastic characteristics of asphalt binders under cyclic loading but also their static viscoelastic characteristics. Based on this idea, the aim of this study is to compare the commonly used models and determine which one(s) can best describe both the dynamic and static viscoelastic characteristics of asphalt binders at intermediate temperatures and are suitable for establishing a fatigue damage model of asphalt binders. The dynamic viscoelastic cha...

Thixotropic Characteristics of Asphalt Binder

Asphalt binder has thixotropic characteristics that significantly affect its overall performance, but specifically fatigue performance, healing performance, and high temperature performance. Therefore, a clear understanding of the thixotropy of asphalt binder, together with proper modeling, is useful in researching the performance of the material. However, research in this area is still in the early stages of investigation. For the study reported in this paper, the thixotropy of four types of asphalt binder is examined by using various methods to establish corresponding thixotropy models. The results show that the exponential thixotropy model, the extended exponential function, and the structural kinetic model can be established by using different methods, and they all reflect the thixotropy of asphalt binder to some extent.