Modelling the linear viscoelastic rheological properties of bituminous binders

Abstract

Rheology involves the study and evaluation of the flow and permanent deformation of time-and temperature-dependent materials, such as bitumen, that are stressed through the application of a force. The fundamental rheological properties of bituminous materials including bitumen are normally measured using a dynamic shear rheometer (DSR), from low to high temperatures. DSR is a powerful tool to measure elastic, viscoelastic and viscous properties of binders over a wide range of temperatures and frequencies, provided the tests are conducted in the linear viscoelastic region. Therefore, the study of bitumen rheology is crucial since its reflects the overall performance of a flexible pavement. However, it is well known that the DSR also has limitations, where the measurements are exposed to compliance (testing) errors particularly at low temperatures and/or high frequencies.In addition, conducting laboratory tests are known to be laborious, time consuming and require skilled personnel. Therefore, this research is conducted to elucidate a better understanding of the rheological properties and modelling procedures of bitumens and bituminous binders.Various materials such as unmodified bitumens, polymer-modified bitumens (PMBs) and bitumen-filler mastics, unaged and aged samples, are used in this study.An extensive literature review was undertaken to identify reliable models that can be considered as a valuable alternative tool to describe or fit the rheological properties of bitumen. These properties are commonly presented in terms of complex modulus and phase angle master curves, together with the determination of shift factor values at a particular reference temperature. In general, the complex modulus and phase angle master curves can be modelled using different techniques; nomographs, mathematical equations and mechanical models. However, the nomographs have become obsolete in recent years and tended to be replaced by the two latter models.Those models are able to satisfactorily describe the rheological properties of unmodified bitumen. However, the observations suggest a lack of agreement between measured and predicted rheological properties for binders that contain a ii phase transition, such as found for highly crystalline bitumen, structured bitumen with high asphaltenes content and highly modified bitumen. An attempt was made to evaluate the validity of several mathematical equations and mechanical element approach using unaged and aged unmodified bitumens and PMBs database. I also owe a profound debt to those whose collective ideas and experiences have contributed greatly for writing the thesis: Prof. Emeritus Montgomery T. Shaw

Short Term and Long Term Aging Effects of Asphalt Binder Modified with Montmorillonite

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The Impact of Ageing on the Bitumen Stiffness Modulus Using the Cam Model

“…Rheological parameters (complex modulus G* and phase angle δ), measured at any temperature and frequency, are described by rheological models to an accuracy acceptable for most purposes (Yusoff & Izzi, 2012). This paper applies the Christensen−Anderson−Marasteanu (CAM) model to describe the behaviour of bitumen and predict the ageing process.…”

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