Plant recycling of pavement materials

Recycling road materials is an absolute necessity in terms of environmental protection: saving natural resources (aggregates), natural spaces (landfills) and energy, and reducing greenhouse gases.

All road materials are recyclable. They can be reused either at the plant or in situ. In-place recycling brings additional transport savings (see [C 5 622] ).

There is a whole range of recycling techniques, the choice of which will depend on the nature of the material to be reused, how it is processed, and the final destination of the resulting product. The degree of penetration of recycling operations varies widely from country to country, and even from region to region. In Northern Europe, recycling is virtually systematic. In the United States, the situation varies greatly from state to state. Whatever the country, recycling developed earlier and faster in highly urbanized areas, faced with the increasing remoteness of quarries and the scarcity of landfill sites.

In France, recycling and reprocessing began in the late 1970s, following the first oil crisis. 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 of materials other than "ultimate" (non-reusable) waste, and requiring the recovery of existing materials in pavements (law of July 13, 1992). Since then, rising energy and bitumen prices have done the rest, so that today, recycling road materials is almost systematic. On the other hand, as we'll see below, their recovery is not yet at its maximum.

In industrialized countries, where there is a high density of fixed materials manufacturing facilities, a large proportion of recycling is carried out in plants. The development of in-plant recycling has required – and still requires – significant investment on the part of companies to adapt and supplement equipment, set up storage platforms for materials to be recycled, organize collection circuits, study formulations and set up appropriate quality assurance plans. These efforts have led to the development of a wide range of techniques and materials, which are presented below.