Coloured Asphalt Pavements: Mix Design and Laboratory Performance Testing

Coloured asphalt pavements are increasingly used in large public areas and at dangerous intersections such as crossroads, roundabouts or pedestrian crossings. In the former application, the role of the coloured pavement is often to give the space a particular aesthetic character or to integrate it well in its surroundings; in the latter, its major role is to enhance the safety of users by improving visibility and road legibility. However, coloured pavements are also subjected to traffic and climate-induced stresses and must, therefore, exhibit a similar mechanical performance as their uncoloured counterparts. Desired colours are obtained by using specific materials such as coloured aggregates, pigments and clear binders. However, the application of latter constituents may affect the performance and durability of coloured asphalt mixtures. Therefore, in a first step, BRRC (Belgian Road Research Centre) determined the characteristics of these particular materials such as the rheological behaviour of clear binders both at high and low temperatures and the stiffening effect of pigments acting as filler. Subsequently, the impact of the material characteristics on volumetric mix design was investigated. In a next phase their effect on the mechanical performance of coloured mixtures was studied in the laboratory. The latter performance was evaluated by testing for water sensitivity, rutting resistance and low-temperature cracking. This contribution summarizes the major findings from the study.