8 tips on how to choose crushed stone: types, fractions, brand, application

Contents

  1. №1.How to get and where to use rubble?
  2. №2.Fractions of rubble
  3. №3.Leschadnost rubble, or geometry form
  4. № 4.Density and strength of rubble
  5. №5.Frost resistance of crushed stone
  6. № 6.The level of radioactivity
  7. №7.Hue crushed stone
  8. №8.The most popular types of rubble( by origin)

It is difficult to name the construction industry, no matter where crushed stone is used. This is an indispensable bulk material, which is characterized by a huge variety of species, and in each case, you should use the material of a particular fraction, strength, flakiness, color and cold resistance. Let's try to deal with the volumetric classification and understand what types of rubble exist, what fractions and brands it is, and how to choose crushed stone so that it optimally matches the scope of application.

№1.How to get and where to use rubble?

Crushed stone is called bulk material, which can vary significantly in color, size fractions, strength and other parameters. The main reason for such a wide variation in characteristics lies in the origin.

By origin, crushed stone is divided into:

  • crushed stone from rocks, which is obtained from stone mining. It can be gravel, granite, quartzite and limestone. This is the most preferred group of materials for use in construction work;
  • Ore crushed stone is obtained by processing rocks of ferrous and non-ferrous metals;
  • secondary and slag crushed stone is obtained from construction waste and production processes. These can be pieces of brick, concrete, asphalt pavement, etc.

The second two types of rubble, though less popular, still find use, because is a wide area of ​​use of rubble .It is used for the manufacture of concrete of different brands, the construction of monolithic structures and foundations, in the production of block building material, for drainage, the creation of various types of pavements, includingbulk garden paths and highways. In addition, rubble is indispensable for arranging runways and railways, and designers loved this material for the possibility of decorating flowerbeds, ponds, embankments and indoor surfaces.

№2.Fractions of rubble

As a result of crushing of raw materials, particles of different sizes are formed, or, in other words, different fractions of rubble. To separate one fraction from another, crushed stone is sifted through a special sieve, referred to as a roar. There are particles of rubble from 3 mm to 300 mm and more.

There are even more grades of crushed stone classifications than fractions themselves. The simplest is the division into five fractions: the first

  • is fragments up to 5 mm , which cannot even be called rubble. Rather, it is a by-product of production, it can be used only for decorative trim tracks;The second
  • is crushed stone with an size of 5-20 mm. .It is the most demanded material in the construction and production of concrete products, it is also used for the construction of roads and the creation of the foundation. Such crushed stone is indispensable in private construction in the preparation of concrete;
  • third - crushed stone 20-40 mm .It is used in drainage works, at construction of tram and railway tracks, and also it can be used at arrangement of the bases of buildings of industrial function;
  • fourth - large crushed stone in size 40-70 mm can be used for drainage, added to concrete and concrete products;
  • Fifth - the largest crushed stone in size up to 300 mm , the so-called.bottlesIts use is very limited, but it is suitable for the decoration of fences, pools and ponds.

There is another, more detailed grading of rubble by size, which implies the distinguishing between standard and non-standard fractions .The standard include such fractions as 3-8 mm, 5-10 mm, 10-20 mm, 20-40 mm, 25-60 mm, 20-70 mm, 40-70 mm. In coordination with the consumer non-standard fractions of 10-15 mm, 15-20 mm, 80-120 mm and 120-150 mm can be produced.

№3.The hawkiness of rubble, or the geometry of the form

In the mass of rubble there are elements of different forms. There are stones that are distinguished by the presence of flat, even edges; they have plate or needle-shaped .Stones with conditionally equal faces are called cuboid .The higher the content of lamellar and needle-like elements in the rubble, the higher the indicator of flakiness .It depends on the performance characteristics of rubble and the scope of its use.

By flakiness, crushed stone is divided into the following types:

  • common rubble with flakiness of 25-35%;
  • improved crushed stone, where part of the needle-like grains is 15-25%;
  • cubical crushed stone with flakiness not more than 15%.

Crushed stone with a low flakiness index is used where it is important to firmly tamp the concrete mix. Needle grains create unnecessary voids in the concrete, so more rubble has to be added, but even so, the compressive strength and the finished material will be lower. Crushed stone with high flakiness is used in drainage works, used in road construction.

№4.Density and strength of rubble

The density of rubble varies from 1.2 to 3 g / cm3 and strongly depends on the type of origin of the material. The higher the density, the more versatile the material. The density and strength of rubble - directly proportional indicators.

Strength is the ability of a material to withstand mechanical loads of different types. Research and determination of the strength mark are carried out by a series of tests, checking the rubble in the cylinder, the shelf drum and squeezing it. Such experiments allow to simulate the real conditions of future operation. By grade, crushed stone can range from M200 to M1600 ( a numerical indicator means the maximum load withstand in kg / cm2) and is divided into the following classes:

  • M200 is very weakly crushed stone, used for arranging drainage systems and creating unloaded dumping;
  • М300-М600 - crushed stone of weak strength, used in the same areas as the crushed stone М200;
  • M600-M800 - medium-strength crushed stone, can be used to create unloaded structures, for example, curtain walls;
  • M800-M1200 - durable crushed stone, the most versatile option that is used when creating foundations, load-bearing walls, supports, fences, etc.;
  • М1200-М1400 - high-strength crushed stone, without which it is impossible to build the foundation of a multi-storey building, bridge piers and hydraulic structures;
  • M400-M1600 - heavy-duty crushed stone, which is used quite rarely and only when creating particularly responsible structures.

is normalized in the rubble, the amount of impurities of weak rocks , because the material strength directly depends on this. To determine this parameter, conduct tests and create pressure on crushed stone of 20 MPa. According to GOST 8267-93, some impurities of low-strength rocks are normalized as follows:

  • for M1600 rubble - no more than 1%;
  • for crushed stone М1000-М1400 - no more than 5%;
  • for crushed stone М400-М800 - no more than 10%;
  • for crushed stone М200-М300 - no more than 15%.

If the content of low-strength impurities is more than 20%, then the material is called gravel and is used only in non-critical works, for example, in the creation of temporary structures, dumping of local roads, etc.

№5.Frost resistance of crushed stone

Frost resistance shows how many cycles of freezing and thawing can withstand crushed stone without losing its basic strength properties. In laboratory conditions, this indicator is determined by drying and saturation of the material in a solution of sodium sulfate. Strength is denoted by the letter F, followed by a number - an indicator of the number of freeze-thaw cycles. The frost resistance of rubble ranges from from F15 to F400 , and in building construction it is best to use crushed stone to not less than F300.

In terms of frost resistance, these types of crushed stone are distinguished:

  • unstable, F15- F Used as bedding, for drainage and for interior work in constantly heated rooms;
  • steady, F50- F150 .It can be used for low-rise residential construction in the southern regions;
  • highly resistant, F200- F This is the most versatile type of rubble that can be used to build critical structures, in high-rise construction, to create various types of concrete goods.

№6.Radioactivity level

Radioactivity is the same important indicator of crushed stone quality as strength or frost resistance. In many ways, the natural radioactive background depends on what kind of gravel is made of. Granite is characterized by increased radioactivity, while quartzite and limestone have a low natural background.

According to the level of radioactivity, crushed stone is divided into the following classes: :

  • Class I is a material with low radioactivity, not exceeding 370 Bq / kg. Universal material that is suitable for the construction of any kind of objects. This rubble is ideal for residential construction;
  • Class II - crushed stone with radioactivity up to 740 Bq / kg. It is only suitable for road construction.

The radioactivity of rubble must be documented, therefore, when selecting and purchasing material, it does not interfere with ascertaining the availability of appropriate certificates and sanitary-epidemiological findings.

No. 7.The shade of rubble

The color of rubble depends on the origin of the material. When it comes to foundation construction, drainage and production of concrete products, the shade of rubble does not play any role. If the material is used for decorative works( for example, for interior decoration of walls, decorating flower beds and ponds), then color is of great importance, blessing, of various weight options. Crushed stone has a huge variety of colors, from gray to reddish, brownish, pink and yellowish.

№8.The most popular types of rubble( by origin)

We have already mentioned that rubble can have a different origin, which determine its performance. Today the most popular are these types of rubble:

  • granite crushed stone - the most durable and versatile. It is obtained from rocks of igneous origin, which may include feldspar, mica and quartz crystals. Depending on the predominance of certain minerals, the color of such rubble may be gray, pink or even reddish. Granite crushed stone is very durable( M1400-M1600), frost-resistant( F300-F400), has a low flakiness, but may have an increased radioactive background, so you should definitely look at the certificates when you buy it. Granite rubble - the best in all respects, therefore, the price for it is appropriate, but still it is most often used in construction. It is used in the production of concrete products, concrete, foundation building, the construction of all types of roads, the construction of important objects, bridges, airfields, etc. There are fractions from 5-10 mm to 150-300 mm;
  • gravel crushed stone is produced by the explosive development of stone rocks and sifting of quarry rock. The shape of the particles can be streamlined and cornerstone, the color is predominantly gray, but there may be elements with a greenish, white and beige shade. According to the main indicator, gravel rubble is inferior to granite, but still its properties allow using the material during the construction of responsible objects. Maximum strength - M1200, it has a good frost resistance and low radioactive background. Since there are a lot of quarries in its mining, and the process itself is not as laborious as in the case of granite, the price for gravel rubble is significantly lower. The fraction of 5-20 mm is used in the production of paving slabs, 5-40 mm - for the production of some concrete products, 20-40 mm - for the production of concrete and dumping roads;
  • quartzite crushed stone is obtained from rocks, the base of which is mineral quartz. In terms of strength, such crushed stone is practically not inferior to granite, it has an insignificant radioactive background and can boast a beautiful appearance, therefore it is often used during decorative works;
  • Calcareous crushed stone is obtained from sedimentary rocks. It has the lowest strength among all types of crushed stone of mountain origin. White, may have shades of yellow, brown and gray. The main advantage is low price. Due to low performance qualities, limestone crushed stone can only be used in the construction of non-critical structures, for example, low-rise buildings and roads with a small load, as well as in the production of simple concrete goods. It is also used for the manufacture of mineral fertilizers, Portland cement, etc.;
  • secondary crushed stone is obtained by processing construction waste, incl.brick, concrete, asphalt, etc. The production process remains the same as when receiving the primary rubble, with the exception of raw materials. The main advantage of such rubble is the price, but in terms of basic indicators it is inferior to the granite counterpart, however, there are areas where the strongest and frost-resistant crushed stone is not required. Maximum strength corresponds to approximately M800, frost resistance - F Secondary crushed stone is used in the construction of roads with a small load, as a large aggregate for concrete, as well as for strengthening weak soils;
  • slag crushed stone is produced by processing metallurgical slags. As a result, there is a material with particles of 5-120 mm in size. Used in the manufacture of cement concrete and to strengthen the foundations in road construction.

As you can see, for any purpose of use you can find rubble with suitable properties and the most favorable price. The main thing when buying to read the documentation.

Tags: Concrete, Construction
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