Aggregates. Origins and characteristics

Aggregates are an essential raw material for building and civil engineering, without which it would be impossible to build structures with today's construction techniques. Aggregates form the backbone of hydraulic concrete and pavement layers, and the quality of housing, engineering structures and roads largely depends on them.

Aggregates are granular materials up to 125 mm in size, plus rockfill larger than 125 mm but weighing 15 t or less. They are designated by their smallest and largest dimensions d and D, the interval d/D being called granular class. This designation admits that some elements can be retained on a square-meshed sieve of aperture D (D sieve) and that others can pass through the d sieve, within the standardized limits allowed.

Three major aggregate families have been defined:

• sands, where d = 0 and $2⩽D⩽6,3mm$ ;

• gravel, where $d⩾1mm$ and $2⩽D⩽90mm$ ;

• the bass, where d = 0 and $2⩽D⩽90mm$ .

The fines constitute the granular fraction passing through the 0.063 mm sieve.

The aggregates most commonly used in building and civil engineering have a true density of between 2 and 3 Mg/m ³ .

European standards replaced French ones in June 2004, bringing to fruition fifteen years of standardization of aggregates in Europe. A number of new features have had a significant impact on the way aggregates are produced, but have not had any noticeable effect on hydraulic concretes and road products: woven cloth sieves have been replaced by perforated plate sieves with square holes for sizes greater than or equal to 4 mm, fines have been determined using a 0.063 mm sieve instead of a 0.080 mm sieve, and so on.

In this dossier [C 902v2], we discuss the origins and characteristics of aggregates. In a second folder , we cover aggregates production, environmental...