Abstract
Asphalt binders incorporating different modifiers is a common practice but empirically driven in most of the cases. Therefore, the fundamental understanding of modification mechanisms in asphalt binders is needed to design polymer modified binders in a controllable manner, especially today in which new modification technologies are proposed. Among others, epoxy-based polymers have been accepted as a promising solution for asphalt binders to develop durable and long-lasting pavement materials. Nevertheless, a relationship between processing of epoxy-asphalt binders and their properties built-up is of high importance to prevent phenomena such as over-curing during the material production. In this research, the use of standard and modulated differential calorimetric measurements is discussed by performing analyses to asphalt binders modified with two epoxy formulations in addition to a commercially available epoxy-asphalt binder as a reference. The kinetic parameters and the Tg change of various crosslinking epoxy-based binders was assessed for the different formulations. According to the results, the Tg is shifting to higher temperatures as cure progresses and crosslinks are formed, with the neat epoxy-based polymer to crosslink faster than epoxy-asphalt binders. Difference on the crosslinking performance between the two epoxy polymers was noticed as well. This research provided valuable insight into the chemical thermodynamics of crosslinking epoxy-asphalt that can help the future material designers to control reaction-induced phenomena, such as the phase separation.
Highlights
Nowadays, the global demand for more durable pavement materials designed and developed to withstand the continuously increasing traffic loads and the extreme temperature fluctuations due to the climate change leads to the use of modifiers of different chemistries and various origins
The kinetics parameters of occurring reactions can be calculated based on the theory discussed earlier and the effect of different formulations in curing of neat epoxy polymers and epoxy-asphalt binders is determined
Two different formulations of epoxy-based polymers were used as modifiers for asphalt binder by having a commercial available epoxy-asphalt binder as reference, and their thermal behaviour under standard and modulated calorimetric measurements was observed
Summary
The global demand for more durable pavement materials designed and developed to withstand the continuously increasing traffic loads and the extreme temperature fluctuations due to the climate change leads to the use of modifiers of different chemistries and various origins. Fundamental understanding of the kinetics and thermodynamics of modified asphalt binders and how these affect the materials properties and subsequently the pavements performance is of high importance, especially today in which new modification technologies, such as epoxy-based polymers, are proposed. In the transition region from an amorphous to a crystalline state, material properties typical of glass are exhibited and stepwise increase of modulus, specific volume, and of thermal expansion coefficient, occur. DSC analyses have been used successfully to evaluate the Tg of asphalt binders of different origins as well as the effect of various asphaltic fractions [16,17,18], modifiers [19,20,21,22] and rejuvenators [23,24] on their glass temperature region. Improvement of polymer-asphalt binder miscibility is reached when the aromaticity of maltenes decreased to certain values [25]
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