Wetting kinetics of a bitumen droplet on a glass substrate

In order to understand how interfacial forces may act in cold mix asphalt just after emulsion breaking, a new experimental procedure has been developed. It tends to mimic what happens when, just after the emulsion breaking, a bitumen droplet is in contact with an aggregate particle. The spreading is monitored by measuring the contact angle of the bitumen droplet on a glass slide over time. As expected, wetting kinetics strongly depends on temperature but equilibrium wetting state (final contact angle) appears to be temperature independent. The main output is the huge effect of the temperature. Indeed, total time for wetting at 35 degrees C is close to 8 h while wetting time at 10 degrees C approaches eight years. The relationship between viscosity at 0 Hz and wetting half-life time was found to be linear. This relationship is intrinsic to the system bitumen/glass/air studied here and derived from the interfacial properties of the three mediums.