Införande av BK4 - Utvärdering av skadeinverkan på de bitumenbundna lagren

Sammanfattning: This study is based mainly on assessing damage done to asphalt by trucks within the load bearing class 4 (BK4). BK4 is a new vehicle rating class for heavy duty vehicles, which refers to an increase of the maximum permissible gross weight to 74 tonnes (for the current 64 tonnes, BK1) for trucks, and which the government has completed implementing the summer of 2018. Since there is still doubt as to what the change of legislation will entail from the viewpoint of asphalt, the hope is that the study should contribute insights on the damage impact done by trucks on asphalt. The report deals with a comprehensive literature study that will provide the necessary information on how asphalt works and behaves under stress, as well as what with the trucks and how they affect the asphalt. In addition, a complementary interview study has been conducted with knowledgeable people within the road and vehicle industry, in order to obtain their views about the change of law and confirm the most significant damage factors with trucks on asphalt. Finally, a calculation study was carried out in the program PMS Object, to which three truck pairs were designed, each of which with BK1 and BK4 equivalents, to compare the degradation of the two bearing classes. The results showed that the degradation was greater for the vehicles within BK4 and that differences in degradation were mainly due to the different ability to load up to the maximum axle load. However, this is followed by objections from the literature study, pointing out that the increased axle count, which the gross weight increase will imply, will affect the recovery effect of the asphalt and provide greater strain in the bottom layer of the asphalt, which in the long run will cause fatigue cracking on the coating. This study should therefore not be seen as a clear answer to the difference in degradation of asphalt pavements between the trucks within BK1 and BK4, but as a guidance for future studies on the subject.