Concerns regarding the winter maintenance of porous asphalt and the assumed increased susceptibility of structures to temperature variations have generally prevented the application of porous asphalt on surface of the structures.
The main objective of the project is the assessment of the applicability of porous asphalt on bridges with regard to winter safety and aquaplaning risks. Furthermore technical construction details and rules for winter maintenance shall be developed.
a) State of the art
The planned program begins with a search of existing literature dealing with studies on safety and winter maintenance on structures coated with porous asphalt. The National Highway Research Laboratories of northern Europe and Dysli Michel, who has many contacts in Canada, will also participate in the inventory of existing information in this field.
b) Structures of behaviour analysis in porous asphalt
Data collection and behaviour analysis of bridges already in service with a coated coating draining will be performed. The difference between dry climate conditions and winter conditions and heavy rain will be compared. Accident statistics will be used. Comparisons before and after the establishment of the drainage will also be conducted for bridges where data are available.
It must result from an analysis of the situation that will highlight the possible increase in the risk level of user safety and the specific maintenance of these structures depending on the situation (altitude, slope, sinuosity) and types of structures (composite bridge, box, etc.).
This census will provide the basis for simulations of the effects of temperature change and the analyses described in the following steps.
Two structures on the A5 in the cantons of Vaud and Neuchâtel between Champagne and Areuse were selected as test boards. It is more accurately the bridge over the Arnon, for the canton of Vaud and Chanélaz bridge for the canton of Neuchâtel. For these works, specific instrumentation will be installed (see below), which will collect the data necessary for the evaluation of their winter maintenance on the one hand, and secondly to evaluate simulation winter behaviour at other types of structures.
The choice of these two test places is justified by their different geometric configurations. Indeed, one is almost horizontal and straight while the other is sloped with a curve drawn in.
It is planned to implement two different types of coating in each direction:
- Monolayer coating porous asphalt
- Bilayer coating porous asphalt
This is justified by the fact that their thermal behaviour is supposed to be different, which will bring an additional degree in the analysis of results.
The instrumentation provided for the two test boards will be compared with instrumentation of the roadway in the vicinity of the structure in order to get a basis for comparison.. This will, in more or less l
The study will allow the Federal Roads Office (FEDRO) set up guidelines or recommendations defining the conditions for establishment of a porous asphalt on the face of the present structures in the network of national roads and define the rules for winter maintenance.