The design of a flexible road paving is closely linked not merely to the structural assessment, but also to the fatigue resistance and, therefore, the cyclic nature of the acting loads, the immediate effect of which has repercussions on the service life of the paving. The service life is a function of the operational limit, which, for a road paving, may be affected both by the presence of cracks and by an excess of deformations (rutting), the nature and development of which depend on the elastic-plastic nature of the bituminous structure.
All the research in the road paving sector therefore tends to analyse the behaviour of a road paving under the effects of repeated loads, that is, under conditions similar to the operational conditions which are considered both during the design and maintenance: the former has a more or less significant technical and economic effect initially, whilst the latter has a major impact on the users of the “road service”, i.e. the drivers, who are forced to live with periodic maintenance works that are necessary for road safety.
The composition of the paving layers and the bituminous materials used are normally taken into consideration during the design phase, but it may also be decided to add elements to the bituminous materials which are able to improve the reinforcement and the drainage, thereby improving the overall load-bearing capacity, reducing the permanent deformations and delaying the development of cracks.