4. Untreated gravel

Untreated gravel is a continuously graded mixture of pebbles, gravel and sand, usually with a proportion of finer particles.

It's the oldest of modern materials. Since it replaced macadam in the 1950s, advances in manufacturing methods have made it a material of ever-improving quality, the most accomplished expression of this technique being "recomposed humidified gravel" or GRH.

Untreated gravel must meet a certain number of conditions in order to be laid in good conditions and to play its role correctly in the pavement. These are defined in European standard NF EN 13285 "Untreated gravel, specifications", which deals with untreated mixtures used for the construction and maintenance of roads, airfields and other traffic areas.

As required by the European standardization system, a national foreword, integrated into...