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 according the necessary flexibility and fatigue behaviour due to the large deflections of an orthotropic steel bridge deck. However, with the growing intensity and axle-loads of the traffic, the problems of rutting and cracking are rising more and more. Especially the rutting problems are related to the “overfilled” character of the bituminous-rich Mastic Asphalt. To solve this problem of non-corresponding requirements, an asphalt mix was developed according the way of function-separation. In this mix the high stability in 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 en 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. In this paper the developments, mechanical characteristics and experiences with the new developed asphalt-mix are reported and evaluated.