This research is intended to contribute toward the understanding, development, andimplementation of a more fundamental design process for bituminous pavementmaterials, utilizing thermodynamic properties of the materials involved. The theorydeveloped by van Oss, Chaudhury and Good forms the basis of this research.Optimization of techniques to characterize surface energy, as well as consideration andevaluation of additional factors that influence adhesion in the presence of water, arepursued. A synthesis of theories and mechanisms of bitumen-aggregate adhesion ispresented, and existing and potential techniques for surface energy characterization arereviewed to establish firm background knowledge on this subject.The Wilhelmy plate technique was scrutinized and improved methodologies andanalysis procedures are proposed. Inverse gas chromatography (IGC) is introduced as analternative technique. A reasonable comparison of total surface energy values formthese techniques with mechanical surface tension values were found. Results suggestthat bitumen surface energies do not vary substantially. Inability of these techniques todetect the effect of a liquid additive is rationalized by the ?potential? surface energyconcept. Suggestions for a more realistic characterization of bitumen polar surfaceenergy components are presented.A static gravimetric sorption technique was employed to characterize aggregatesurface energies. Dynamic vapor sorption was identified as a candidate alternativetechnique for aggregate surface energy characterization.A study on the effect of pH on surface energy components of water revealed that thiseffect is practically negligible. Calculation of the free energy of electrostatic interaction(DGEL) indicated that this term contributes less than 1% to the total free energy ofadhesion. Despite this finding, it is shown that DGEL alone is able to distinguishmoisture sensitive mixtures. The significance of electrical phenomena at the interface iselucidated through another mechanism following the work of M.E. Labib. Therelationship between pH and electron donor-acceptor properties of aggregate surfaces ispresented. The Labib approach potentially offers the solution to quantify the effect ofpH on adhesion. In addition, it should be possible to resolve issues with the acid-basescale proposed by the founders of the current theory, by replacing it with a moreabsolute donor-acceptor scale.
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