Validation of a hydraulic model to prevent emulsion flowing in chip sealing

Chip sealing is a pavement surface treatment that consists in the application of an asphalt binder (bitumen or bituminous emulsion) on an existing pavement followed by the spreading of aggregate chips and by the rolling of the surface, in order to embed the aggregate into the binder. This treatment is typically used as preventive maintenance technique of asphalt pavements, in order to seal fine cracks and improve skid-resistance of road surfaces. Moreover, chip sealing is often employed on rural roads, that carry low traffic volumes and are often characterized by critical conditions such as small radius of curvature and/or high longitudinal slopes. In the latter case, the application of the bituminous emulsion becomes a crucial concern as an excessive flowing of the bitumen could take place due to the high pavement slope and its spreading could become not uniform. In order to investigate these aspects, in this study ahydraulic model of the theoretical flow of bituminous emulsions on high longitudinal slope road surfaces was proposed and validated through a laboratory experimental investigation. To this aim, an original laboratory equipment (Chip Seal Laboratory Simulator), that allows the simulation of the most critical conditions during field activities, was properly designed and realized. The theoretical analysis and the experimental validation suggested practical recommendations in terms of longitudinal working speeds in critical contexts, very usual in practice.