Assessment of the environmental effects of bitumen emulsions in road applications - Elaboration of an experimental methodology for grave emulsions
Résumé
At room temperature, bitumen is solid, and its handling in these conditions is not easy. Several techniques are used to make it more malleable, emulsification is one of them. Bitumen emulsions can, among other advantages, be used between 20 and 75°C. Bitumen emulsions require the use of an emulsifier as bitumen and water are immiscible. The main emulsifiers belong to the family of amines. The application of bitumen emulsion on the road surface involves the rupture, or the breaking, of the emulsion, i.e. the separation of the phases that compose it, especially during the compaction phase [1, 2]. At the breaking of the emulsion, the emulsifier is expected to remain at the interface between gravels and the bitumen film. However, during this breaking, a part of the emulsifier is driven by the breaking water. In the case of a surface dressing, exudation of breaking water is not visible to the naked eye: water is expected to evaporate during the implementation while the emulsifier remains on the roadway. Rainfall may then lead some excess emulsifier outside of the roadway and toward potential targets (fauna and flora). Some compounds composing these emulsifiers are recognized to be hazardous to the environment due to their intrinsic properties (some are classified R50 or R53). This study aims to propose a laboratory method for the qualification of the environmental effects of bitumen emulsions in realistic use scenarios (i.e. no accidental scenario is considered here). Repeatability of the results obtained with this testing strategy is also investigated