A new type asphalt surface layer for steel bridge decks

The usual type of asphalt layers for steel bridge decks in the Netherlands is mastic asphalt. The properties of this type of asphalt mixture are determined by the necessary flexibility and fatigue behaviour due to large deflections of an orthotropic steel bridge deck. However, with the growing intensity and axle-loads of the traffic, problems of rutting and cracking are increasing. The rutting problems are related to the overfilled character of the bitumen-rich mastic asphalt. To solve this problem of non-corresponding requirements, an asphalt mixture was developed with high stability in a vertical direction for carrying the traffic load is combined with the required horizontal flexibility to follow the high deflections of the bridge deck. The result is an asphalt mixture that can produced and laid like normal hot asphalt. This solves also the problem of the lack of special equipment for producing and laying mastic asphalt in the Netherlands. The development, mechanical characteristics and experiences with the new developed asphalt mixture are reported and evaluated. For the covering abstract see ITRD E157233