Effect of high water salinity on the adhesion properties of model bitumen modified with a smart additive

The interfacial behavior at the asphalt/salt solution is really important to understand and improve the road durability near sea areas or in zones where salt is added to avoid traffic problems (i.e. mountain areas in winter). Consequently, in an attempt to understand the problems, dynamic interfacial tensions between bitumen modified with selected additives and aqueous salt solutions were measured to simulate the effect of salinity on the adhesion properties of asphalt in sea areas. In addition, contact angle and boiling water tests were performed to understand better the salt effect. Three different surfactants were used in this work to obtain modified bitumen solutions: a cationic, a nonionic organosilane surfactant and a primary alkyl amine surfactant. Generally, the salt had a pejorative effect on the adhesion of the bitumen on the stones, but the presence of small amounts of organosilane surfactant looked likely to have the best performance and then it was also tested against different salt concentrations. All the dynamic interfacial results were studied and analyzed thanks to the Ward-Torday model and the Graham and Phillips approach, obtaining information about the interfacial properties of the asphalt/brine interface. Thanks to these results, the complex adhesion phenomena at the brine interface could be better understood with an improvement effect on the additives to be used to avoid the premature ageing of the road surfaces.