Roads - Flexible and semi-rigid pavement materials

The "raw materials" of which the materials used in pavement bases are made are described in various articles of the Construction treatise, and in particular those listed in the To find out more.

It is from these various components that the materials making up the various pavement layers are manufactured, the aim being that, through appropriate formulation and manufacturing and laying conditions, they best meet the requirements listed in article [C 4 316] . As the latter indicates, these requirements are of two kinds:

• withstand the repeated action of rolling loads, especially heavy goods vehicles;

• guarantee motorists quality pavement maintenance services.

Before examining the nature of the most suitable materials, layer by layer, starting with the subgrade, it should be stressed that traditional approaches are being radically altered by the development of techniques for recycling and reprocessing existing pavement materials.

These techniques, described in articles [C 5 620] and [C 5 622] , from which the following passages are taken, clearly meet "... a pressing need from the point of view of environmental protection and sustainable development: saving natural resources (aggregates), natural spaces (landfills), energy and reducing greenhouse gas emissions.... Although they first appeared in the late 1970s, following the first oil crisis, their development was then rather slow, due to the abundance of quarries and asphalt plants. However, the situation began to change significantly in the 1990s, with the introduction of stricter legislation, in particular prohibiting the landfilling...