Crushed stone fractions - what they are and where they are used

Crushed stone fractions - what they are and where they are used

Crushed stone stands as a paramount building material among all natural materials used in construction. The choice of crushed stone largely depends on the type of work being performed, as well as the cost-quality ratio. Crucially, its compatibility with other building materials, such as brick, is a significant factor to consider. Therefore, a responsible approach is required when selecting building materials. To choose a good quality brick, visit an online store. Here, you can find various types of bricks that best meet your needs and are compatible with the corresponding type of crushed stone. The fractions of the crushed stone play a decisive role in its selection.

Crushed stone fractions refer to the largest permissible sizes of each individual stone (grain sizes). Main fractions include: 5–10, 5–20, 10–20, 20–40, 20–65, 25–60, 40–70mm. Secondary fractions are: 0–2, 0–5, 0–15, 0–20, 0–40, 0–60, 2–5mm. Occasionally (though very rarely), fractions of 70–120mm, 120–150mm are used.

Granite crushed stone fractions of 5–20mm have gained the greatest popularity in the market, with 5–15mm fractions being used less frequently – in the production of concrete, asphalt, and reinforced concrete structures. Fractions of granite 20–40, 20–65, 25–60, 40–70 mm also remain in constant demand, mostly used in construction and repair of railway embankments, tram tracks, and highway bases. They are also used in building foundations and for crushing into smaller size fractions.

In crushed stone fractions, the content of clay and dust particles (smaller than 0.05mm) is regulated. Also identified are clay lumps, ranging in size from 1.25mm to the size of the largest grain of the fraction. For all types of crushed stone, the concentration of clay in lumps and clay particles should not exceed 0.25%. In crushed stone produced from metamorphic and igneous rocks, the clay concentration should not exceed 1% by weight.

The presence of crushed stone grades allows for its classification into groups: strong M800–1200, highly strong M1200–1800, medium strength M600–800, weak strength M300–600, excessively weak strength M200.

Also regulated is the content of grains from weak rocks, which have a compressive strength limit of the original rocks in a water-saturated state of up to 20MPa. According to GOST 8267-93, crushed stone grades M1400, M1200, M1000 should not contain more than 5% weak rock grains, in grades M800, M600, M400 - more than 10%, and in grades M300 and M200 - more than 15% of the total weight.