LAUSR

Abstract The present study evaluates two different methods for selection of probe liquids to determine the surface free energy (SFE) of asphalt binders: (i) Condition Number (CN) of probe liquids, and (ii) plot between cosine of total SFE ( ϒ L Cosθ) and total SFE of probe liquids ( ϒ L ) . Five different probe liquids, i.e. Water (W), Formamide (F), Ethylene Glycol (E), Diiodomethane (D), and Glycerol (G) were selected. Overall, ten different combinations of probe liquid triplets (W-G-F, W-G-E, W-G-D, W-F-E, W-F-D, W-D-E, G-F-E, G-F-D, F-E-D, and D-E-G) were formed to examine CN and plot of ϒ L Cosθ versus ϒ L . Three asphalt binders, namely unmodified (VG30), SBS polymer modified binder (PMB40) and crumb rubber modified (CRMB60) binders were selected for the present study. The contact angle of asphalt binders was measured using sessile drop method, and SFE of each of the selected asphalt binders was determined for all ten combinations of probe liquids. Thereafter, CN of probe liquid triplets was determined using Singular Value Decomposition (SVD) method. In addition, ϒ L Cosθ versus ϒ L plot was made for triplets using the measured contact angles of probe liquids. The CN approach and ϒ L Cosθ versus ϒ L plot were compared based on binder’s total SFE to identify a better approach for selecting appropriate probe liquid triplets. CN approach was observed to be superior compared to the plot of ϒ L Cosθ versus ϒ L . In fact, it was observed that the plot approach may not be valid for asphalt binders.