Asphalt surfacing on timber bridges

It is difficult to get adequate information about the load-bearing properties of the different asphalt systems which are used for the surfacing of modern timber road bridges. The authors have participated in a research project to investigate the load-bearing behaviour of different, asphalt-based road surfacing systems under service loads. First, suitable material combinations and layer compositions were selected for detailed research. The transfer of horizontal forces through the composite construction was a special research interest. A number of test series was carried out to investigate the adhesion between the surfacing and the timber deck. The test results were comparable to those obtained for surfacing placed on concrete and steel bridge decks. The tests confirm that the requisite bonding strength can be achieved with similar systems such as those used in steel and concrete bridges. Structural recommendations for the practical application are also presented in the paper.