Study of phase behavior of epoxy asphalt binders using differential scanning calorimetry

Apostolidis, P.; Elwardany, Michael; Andriescu, Adrian; Mensching, David J.; Youtcheff, Jack

doi:10.1016/j.conbuildmat.2023.130566

Study of phase behavior of epoxy asphalt binders using differential scanning calorimetry

Title

Study of phase behavior of epoxy asphalt binders using differential scanning calorimetry

Author

Apostolidis, P. (TU Delft Pavement Engineering)
Elwardany, Michael (Florida State University)
Andriescu, Adrian (Turner-Fairbank Highway Research Center)
Mensching, David J. (Turner-Fairbank Highway Research Center)
Youtcheff, Jack (Turner-Fairbank Highway Research Center)

Date

2023

Abstract

Glass transition parameters can be used to study the miscibility, or lack of it, in polymer-modified asphalt binders. In this study, the contribution of thermodynamics of mixing to glass transition was quantitatively assessed in a differential scanning calorimeter for four asphalt binders partially and fully replaced by an epoxy system. The values of heat capacity (C_p) and, subsequently the glass transition temperature (T_g) of all binders were determined to quantify the miscibility based on the entropic changes. Emphasis was also given to examining the enthalpy of mixing as a function of epoxy system composition during curing to ensure that these binders were completely crosslinked for further analyses. In all cases, the positive deviations of the measured T_g of epoxy-modified asphalt binders (T_g,mix) obtained from the ideal mixing rule led to negative values of the entropy of mixing (ΔS_mix^c), dictating the presence of internal repulsive forces between the asphalt and epoxy components. Softer binders were associated with binders of low deviations of T_g,mix values from the ideal mixing rule. Lastly, the partial replacement of asphalt binders by the epoxy system increased the T_g and decreased the amount of ΔS_mix^c, and such performance imposes the formation of immiscible products.