Physicochemical Characterization of Binder-Aggregate Adhesion Varying with Temperature and Moisture

Interfacial bonding among asphalt binder and aggregates plays a significant role in asphalt concrete performance and potential for moisture damage. Previous studies have established experimental procedures to quantify the adhesive bond strength between asphalt binder and aggregates using techniques such as contact angles, adsorption isotherms, and enthalpy of immersion. This research study expands on the previous efforts by development of an experimental procedure and analysis method capable of assessing the effect of temperature on the binder-aggregate adhesive bond and experimental quantification of the effect of moisture on the adhesive properties of binder-aggregate systems. Results show that the the binder-aggregate adhesive bond is reduced with increasing temperature but the relative ranking of binder-aggregate interaction prevails over the in-service temperature range (i.e., 10-50°C). Additional experiments were conducted with respect to water-aggregate affinity considering (1) hydrophilicity of the aggregates, and (2) evaluation of binder-aggregate bond when moisture is present at the binder-aggregate interface. The proposed microcalorimetry technique is recommended to evaluate binder-aggregate interactions at various conditions. Advantages of microcalorimetry include direct measurement and flexibility of aggregate conditioning to mimic realistic production conditions. Similar experimental protocols could be employed to better understand the mechanisms and implications of using different types of materials, additives, and production techniques in the asphalt industry (e.g., lime treatments, recycling processes, and cold asphalt technologies); continued research is recommended.