Crushed stone

Loose natural material (crushed limestone) is the main component of many building products used in the construction of buildings, the construction of roads and railways. Technical characteristics to determine the scope of application of limestone crushed stone, it is necessary to know its main characteristics:

Strength of crushed stone. It is determined by crushing in a cylinder, after which the material is assigned a grade:

• High strength from M1200
• durable grades from M800 to M1200
• medium-strength M600-M800
• low-strength crushed stone M300-M600

The strength of limestone crushed stone rarely exceeds the M800 grade.

Flatness. This is the percentage of flat and needle-like grains in the crushed stone, which determines its bulk density, i.e. the presence of voids in the volume. The lower the value, the stronger the strength of the embankment will be. The flatness of lime gravel is 10-12%.

Frost resistance. Shows the theoretical number of times that crushed stone is able to freeze and thaw without loss of strength. Limestone crushed stone has an average frost resistance of F150.

Radioactivity. Loose limestone materials have the lowest background radiation in comparison with other types of crushed stone — about 55 Bq / kg. The highest permissible radiation level of 370 Bq / kg has granite raw materials.

Fractions of limestone crushed stone. In the production of crushed stone, it is sorted through specialized sieves into fractions — the size of the grains in the batch. There are three main fractions for lime material:

• Fine fraction — 5-20 mm.
• Medium — 20-40 mm.
• A large fraction is limestone crushed stone (40-70 mm).
• Crushed stone with grains of non-standard size of 70-120 mm and 120-400 mm is called rubble stone.

Advantages and disadvantages. Limestone crushed stone has a number of advantages. These include:

• frost resistance;
• resistance to temperature changes;
• low cost;
• good performance properties for certain types of work (due to its low strength, limestone crushed stone is perfectly tamped, perfect for creating a dense base);
• environmental friendliness (radioactive indicators of limestone are quite low, which makes crushed stone completely safe).

But this building material has disadvantages:

• It is destroyed by acids.
• It has a relatively low strength.
• It does not tolerate prolonged contact with water.

Application: Limestone crushed stone of fine fraction is used as a filler for the production of concrete grades M100 and M200. The small size in this case provides good adhesion of concrete and reinforcement. Such concrete is used in the installation of a blind, porch, pillows for the foundation, garden paths and the construction of monolithic walls. Scaffolding and ring drainage significantly extend the life of the building. But products based on limestone can not be used in structures that are affected by an acidic environment. In addition, when using limestone crushed stone in the foundation, high-quality waterproofing is necessary.

Limestone crushed stone of the different fractions is used to install a pillow under the base. Before the construction of the foundation, a drainage layer of sand, gravel and gravel is created. The use of lime crushed stone is advisable, since lime creates a good connection between all the components of the layer. The normal thickness of the layer does not exceed 200 mm and it shall be located above the line of the groundwater level.

№	Limestone crushed stone fraction (mm)			Requirements of GOST 8267-93
				For igneous intrusive rocks		For sedimentary and metamorphic rocks
		Crushed stone grade by fragmentation	Mass loss during crushed stone testing, %	Crushed stone grade by fragmentation	Mass loss during crushed stone testing, %	Crushed stone grade by fragmentation	Mass loss during crushed stone testing, %
1	5	1200	10,64	1400	Up to 12	1200	Up to 11 inclusive
2	5-10	1000	11,32	1400	Up to 12	1200	From 11 to 13
3	20-40	1000	11,35	1400	Up to 12	1200	From 11 to 13
4	40-70	1000	11,40	1400	Up to 12	1200	From 11 to 13