Aggregates. Origins and characteristics

Aggregates are an essential raw material for building and civil engineering, without which it would be impossible to construct buildings using current construction techniques. They form the skeleton of hydraulic concrete and the framework of road surfaces, and their quality largely determines the quality of housing, engineering structures, and roads.

Aggregates are granular materials with dimensions not exceeding 125 mm, plus rock fragments larger than 125 mm but weighing less than or equal to 15 t. They are designated by their smallest and largest dimensions d and D, with the interval d/D being called the granular class. This designation allows for elements to be retained on a square mesh screen with an opening of D (screen D) and others to pass through the screen d, within the permitted standard limits.

Three main families of aggregates are thus defined:

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

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

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

Fines are the granular fraction that passes through a 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 standards in June 2004, marking the culmination of fifteen years of standardization of aggregates in Europe. Several new developments have significantly changed practices but have had no significant impact on hydraulic concrete and road products: the replacement of woven mesh screens with perforated metal screens with square holes for sizes greater than or equal to 4 mm, the determination of fines using a 0.063 mm screen instead of a 0.080 mm screen, etc.

In this file [C 902v2], we discuss the origins and characteristics of aggregates. In a second file...