Types of crushed stone by origin. What is natural gravel and its characteristics

Non-standard:

Flakiness

Crushed stone of increased flakiness.

Crushed stone of fraction 3-8 and 5-20 is used for the production of concrete and products from it. Fraction 20-40 is most often used during the laying of foundations of buildings (as part of the "pillow"), and fractions 25-60 and 40-70 are used in road construction.

Crushed stone of fraction 25-60 can be used exclusively for ballast layer railway track(GOST 7392-2002). In construction, in accordance with GOST 8267-93, other crushed stone fractions are used.

Varieties of rubble

Granite crushed stone

Granite crushed stone is crushed stone from hard rock granular structure, which is the most common on Earth. Granite rock represents magma hardened at great depths, composed of well-formed crystals feldspar , quartz , micas etc. And it has a color of red, pink or gray, set off from the predominance of spar and mica in it. Lumps are usually obtained by explosion monolithic rocks, then they are crushed in a machine, and the resulting crushed stone is sieved in fractions. This is the last stage of crushed stone production.

Fractions granite rubble

• 0-5 mm (granite screening) - the smallest fraction of crushed granite, in the strict sense - does not apply to crushed stone, but is a by-product in its manufacture. It is used as a decorative material for finishing, as well as for filling tracks and roads, children's and sports grounds; for the manufacture of concrete products, in particular with the surface of "washed concrete";
• 5-10 mm is the finest commercially available fraction. Used in production concrete and structures made of it to optimize the fractional composition of coarse aggregate, for example, in the production of floor slabs without formwork;
• 5-20 mm (mixture of fractions 5-10 and 10-20) - uses the greatest in demand... Used in production concrete and constructions from it, in fundamental works, when filling pavement constructions, pavement, road and airfield base coatings;
• 20-40 mm - middle fraction. It is used in the production of concrete, reinforced concrete structures, in the construction of roads and railways, tram lines, when laying the foundation and erecting industrial buildings;
• 20-70 mm, 40-70 mm - coarse fraction, used in the production of concrete, massive structures from it and for work with a large volume of concrete. It is also used in road construction within settlements, in the construction of industrial buildings and structures;
• 70-120 mm, 120-150 mm, 150-300 mm (BUT) - rarely used. It is used for decorative purposes, usually for finishing fences, reservoirs, pools.

These are the standard, most common ways of using these crushed granite fractions, however, for each of them there are many options application.

According to its technical characteristics, crushed granite is durable(grade 800-1200) and high-strength (grade 1400-1600), frost-resistant(grade 300-400), with low flakiness(5-23%) and 1 class of radionuclidity (A (ef)<370 Бк/кг). Показатели содержания radionuclides, harmful components and impurities are absent or do not exceed the norms, which is confirmed by the corresponding certificates and conclusions issued after the research.

Crushed gravel is used for foundation work, for concrete, in production Concrete goods, during construction roads.

There are two types of crushed gravel:

• Crushed crushed stone is ordinary natural or crushed,
• Gravel- these are rounded pebbles, as a rule river or marine origin.

Crushed slag is used not only as a filler for cement concretes, but also in road construction for strengthening foundations and installing asphalt concrete pavements.

Crushed stone grade by strength

The strength of crushed slag is characterized by its brand. For crushed stone from blast-furnace slag used as aggregate for heavy concrete, five strength grades have been established:

Crushed stone of the M1200 brand can be used in the manufacture of concrete of the M400 brand and higher, M1000 - of the M300 brand, M800 - of the M200 and M600 brands - below the M200. Crushed stone of low grades is also used in the manufacture of concretes of higher strength, but after appropriate verification and a feasibility study.

Links

• GOST 8267-93 Crushed stone and gravel from dense rocks for construction work. Technical conditions. Retrieved March 18, 2009.
• GOST 8269.0-97 Crushed stone and gravel from dense rocks and industrial waste for construction work. Physical and mechanical test methods. Retrieved March 18, 2009.
• GOST 8269.1-97 Crushed stone and gravel from dense rocks and industrial waste for construction work. Chemical analysis methods. Retrieved March 18, 2009.
• GOST 26644-85 Crushed stone and sand from slag of thermal power plants for concrete. Technical conditions. ... Retrieved March 18, 2009.
• GOST 22856-89 Decorative crushed stone and sand from natural stone. Technical conditions. Retrieved March 18, 2009.
• GOST 5578-94 Crushed stone and sand from slags of ferrous and non-ferrous metallurgy for concrete. Technical conditions. Retrieved March 18, 2009.

• GOST 22263-76 Crushed stone and sand from porous rocks. Technical conditions. Retrieved March 18, 2009.

Clastic rocks

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See what "Rubble" is in other dictionaries:

Crushed stone- - inorganic granular bulk material with grains larger than 5 mm, obtained by crushing rocks, gravel and boulders, incidentally mined overburden and enclosing rocks or substandard waste of mining enterprises for ore processing ... ... Encyclopedia of terms, definitions and explanations of building materials

The word "gravel" can mean both natural material and artificial (expanded clay) produced industrially. Both natural and expanded clay gravel are popular with builders, concrete manufacturers, designers and other professionals.

Description

Natural gravel is a natural material that is formed under the influence of wind and the destruction of rocks. Depending on the type of occurrence, it can be mountain (or ravine), river, lakeside, or even glacial.

Rock gravel has a slightly rough surface. It contains clay, dust, sand, organic matter and other impurities. If the percentage of sand exceeds 25-40%, it is a sand-gravel mixture.

Slightly cleaner in composition sea and river gravel. But at the same time it is smoother, therefore it is characterized by poor adhesion to the bonding agent.

Usually builders choose rock gravel because its technical qualities are slightly better than other types. It is used for the construction of routes, foundations, filling various sites, obtaining roofing materials.

Gravel has various shades: black, yellow, white, gray-blue, brown, pink. Its color may change slightly under the influence of light or humidity. That is why it is popular in landscape design: when decorating summer cottages, paving garden paths, laying out flower beds, etc.

GOST for natural gravel

Whether it is permissible to use gravel for certain purposes depends on its physical and technical qualities, which are approved at the level of GOSTs and technical instructions.

For gravel and crushed stone with an average density of granules of 2-3 g / cm3 and used to obtain heavy concrete, road and other construction works, GOST 8267-93 “Crushed stone and gravel from dense rocks for construction work. Technical conditions ".

In this standard, gravel from mountain weather refers to granular material that has an inorganic base, with a grain size of more than 5 mm, which is formed during screening of a gravel-sand mixture.

The standard specifies the requirements for the size of fractions, the shape of granules, strength properties, the percentage of granules of weak breeds and harmful components, frost resistance, nuances of acceptance, control methods, requirements for transportation and storage, etc.

There is also GOST 8269.0-97, which describes in detail methods for determining the main physical and mechanical properties of a material.

Most often, the determination of future properties and their compliance with GOST occurs, which includes mining in open pits, washing and sorting.

Fractions

In the buying process, special attention should be paid to the gravel fractions. They are determined both by the size of the granules and by the density. The grains can be from 5 mm up to 70 mm in size.

Main gravel fractions (mm):

1. 5(3)-10;
2. 10-15;
3. 10-20;
4. 15-20;
5. 20-40;
6. 40-80(70);
7. combination of fractions 5 (3) -20.

Material in the form of other combinations of different fractions and larger grains can be produced by agreement between the manufacturer and the buyer.

Gravel 3-10 mm in size is used in the arrangement of play and sports grounds, private beaches, for filtering wells or springs, in floristry. Gravel 10-20 mm in size is used to obtain lightweight concrete. In 1 m3 of concrete, there is approximately 1 ton of gravel in the form of filler.

Large fractions of the order of 20-40 mm are used for the construction of routes, bridges, aerodrome coatings, etc. Gravel 40-70 mm in size and above is used mainly as a decorative material. They decorate aquariums, swimming pools, animal cages, pave streets, and use it in the construction of dams.

Thanks to its versatility, combined with ease of use and low cost, the gravel got wide.

Specifications and properties

Gravel acquires some parameters already in the process of its preparation and processing (sieving, cleaning, mixing, etc.). Such training helps to obtain material that is fairly homogeneous in composition and to achieve compliance with official norms.

The main properties of natural gravel:

• the density of the material may fluctuate depending on its type. The average gravel density is 2.6-2.7 t / m3. Bulk density can range from 1.43 to 1.61 t / m3;
• the volumetric weight is 1600 kg / m3, and the specific weight is 1400 kg / m3;
• the shape of the grains can be round, rounded-angular, angular. According to GOST 8267-93, in the composition of gravel there can be no more than 35% (by weight) of grains that have an acicular or lamellar shape;
• the strength of the material is expressed in grades of crushing (or compression) in the cylinder. There are such grades for strength: DR8, DR12, DR16, DR24. The compressive strength is 1.5 t / cm2;
• for gravel, which is used in road construction, an additional measure of abrasion is established, which is determined as a result of tests in a shelf drum. At the same time, grades I-I, I-II, I-III and I-IV are distinguished;
• based on the degree of frost resistance, gravel grades are distinguished from F15 to F400.

For comparison, we present a table comparing the characteristics of natural gravel with artificial (expanded clay):

How to distinguish gravel from pebbles and rubble

The word "gravel" usually means rock gravel mined in quarries. Pebbles are the same river or sea gravel formed as a result of sanding and grinding small flat stones with sand and water. Thus, pebbles are a subtype of gravel.

Pebbles can have different colors. Most often, there are multicolored pebbles or pebbles of pink, yellow, gray, brown or marble shade. Sea pebbles have a flatter shape than river pebbles.

You can distinguish gravel from crushed stone by its shape and texture. Crushed stone has a rough surface and an acute-angled shape, while gravel is smoother and more rounded.

Crushed stone is formed in the process of crushing rocks in a quarry or during the processing of industrial waste. Thus, gravel is a material formed naturally, and crushed stone is an industrial one. Sometimes, in order to improve the quality of the adhesion of gravel to the solution, it is crushed into smaller fractions, obtaining crushed stone.

What is gravel, how it looks and how it visually differs from crushed stone can be seen in the photo-picture below:

Which is better and cheaper: gravel or crushed stone

Due to its irregular shape, crushed stone forms a more reliable adhesion to the mortar than gravel. Thus, in terms of performance, crushed stone is significantly better than gravel.

The main advantage of gravel is the lower price. It is about 20% cheaper than crushed stone, so it is often chosen as an aggregate when making heavy concrete. Gravel is often used for the construction of low houses in summer cottages and even for the formation of a foundation.

What to choose - crushed stone or gravel - also depends on the properties of the concrete. When the concrete is very strong, it is advisable to use crushed stone. For moderate strength concrete, inexpensive gravel is suitable.

Crushed stone and gravel are used in almost all construction work. These naturally occurring minerals are formed from rocks. Outwardly, they are very similar, however, upon closer examination, it becomes obvious that bulk materials have significant differences. To understand what granite crushed stone is, consider all varieties of this raw material.

Features of gravel

If we talk about what gravel is, then first of all it is worth paying attention to the form of this mineral. Round shaped multi-colored stones are obtained due to the natural destruction of rocks.

Depending on the fraction of this raw material, three types of gravel are distinguished:

• from 1 to 1.25 mm - fine gravel;
• up to 5 mm - medium;
• 10 mm - coarse gravel.

Raw materials cost about 1,700 rubles per cubic meter.

Since this material is mined from different regions, there are quite a few varieties of this raw material.

There are the following types of colored gravel:

• River. This type of raw material is extracted from river beds, after which the material is sieved to separate the sand from it. River gravel is frost-resistant and durable.
• Mountain. The main difference between this raw material is the rough surface of the particles. Rock gravel contains a lot of impurities (clay and dust), so it is more often used in road construction.
• Decorative. This material is widely used in landscape design (in the manufacture of gravel paths in the country, to create a drainage system for plants and decorate reservoirs). Decorative material comes in a variety of colors and fractions.
• White gravel. This type of gravel is used both for garden paths and for decorating flower beds. In addition, the decorative material allows you to: slow down the growth of weeds, reduce temperature drops in the soil and reduce moisture evaporation. Such a stone looks especially beautiful with proper lighting in the evening.
• Rounded. This decorative material is used for flooring and roofing. It also makes beautiful and practical gravel paths.

However, today not only colored gravel is used, but also specialized:

Building

Inorganic bulk building material has the following properties:

• Fraction size from 3 to 150 mm.
• Bulk density from 1.4 to 3 g / cm 3.
• The specific gravity is about 1400 kg per cubic meter.
• Compressive strength 1.5 t / cm 2.
• Frost resistance from F15 to F

He also considers this raw material to be the most durable.

Shungizite

This environmentally friendly raw material is considered a versatile thermal insulation material with a long service life. If you use shungizite gravel as an aggregate for concrete, you will get a lightweight and frost-resistant building material. Also, high-quality gravel paths are obtained from it, which will not accumulate moisture.

Silicic

Raw materials of this type are most often used as a bottom filter for summer cottages. Due to its properties, silicon stone is able to retain organic matter and heavy metals. The water that has passed through the filter is distinguished by its purity and the best taste characteristics.

Glacial

This raw material has good adhesive properties, which makes it often used in the construction of monolithic concrete structures. Concrete on such gravel is characterized by increased strength and durability.

Washed

Unlike other types of gravel, only in the washed raw materials there are no impurities that can worsen the characteristics of the concrete solution. Thanks to the use of washed gravel (it is better to buy land gravel, not river gravel), the concrete mass will not crack, and empty cavities will not form in it.

There is also such a variety of gravel as gravel mix.

Gravel mixtures

Today, enriched sand and gravel mixtures or, as they are also called, OPGS, are often found on sale. Such compositions are mixed with cement and water to obtain a higher quality building material. In the cooking process, it is important to adhere to certain proportions and quality of the components, otherwise the use of OPGS will not be justified.

Healthy! Natural mixtures contain no more than 20% of gravel, after enrichment, its content increases to 75%.

The sand and gravel mixture contains the following components:

• gravel crumbs or gravel of different fractions - 70%;
• sand without impurities - 30%.

Also, the composition is allowed to contain clay, but not more than 1%.

Along with enriched sand and gravel mixtures, gravel screenings are also on sale. In fact, this raw material is waste that is obtained in the process of crushing rocks.

The cost of such screenings is much lower, therefore, thanks to this material, it is possible to significantly reduce the cost of construction work. Gravel waste is used both in the manufacture of reinforced concrete structures and in the design of the site (gravel paths as in the photo, sports grounds, flower beds and much more).

To determine how gravel differs from crushed stone, consider the features of another building material.

Features of rubble

Crushed stone is an inorganic raw material that is mined by crushing granite, boulders, limestone and other rocks. The main difference between crushed stone and pebbles is its rough surface and the presence of very sharp corners. In addition, crushed stone is large, so it is rarely used for suburban walkways. Due to the larger fractions, this material has good "adhesion", therefore it is successfully used as a filler for building mixtures.

Healthy! If we talk about the differences between gravel crushed stone and ordinary, then you should pay attention to the method of extraction of raw materials. Crushed gravel is mined by crushing rocks, so it has sharper corners. Ordinary crushed stone is formed independently, under the influence of water.

If we talk about the size of stones, then according to GOST there are the following categories:

• Up to 5 mm (dropout), suitable for paths, pitches and as ice protection.
• From 5 to 10 mm, used as aggregate for concrete mixtures.
• From 10 to 20 mm, used to create the foundation for the building.
• From 20 to 40 mm - for complex structures of high weight.
• From 40 to 70 mm - for the construction of road surfaces and multi-storey buildings.
• From 70 to 120 mm - as decorative elements.

It is also worth paying attention to how much a cube of rubble weighs.

Based on this, we can conclude that the bulk density of some types of crushed stone is much lower than that of gravel.

The cost of crushed stone is about:

• 1,500 rubles for 1m 3 of limestone raw materials;
• 2 100 rubles - granite;
• 1 150 rubles - slag.

Crushed stone classification

Crushed stone is classified according to several criteria. First of all, you should pay attention to its brand:

• M 1200 - 1400 - high strength material;
• М 800 - 1200 - durable crushed stone;
• М 600 - 800 - raw materials of medium strength;
• М 300 - 600 - low-strength material;
• M 200 - crushed stone of the lowest strength.

Also, crushed stone is distinguished by the number of irregular grains:

• Group 1 - the content of grains, in which the length is 3-4 times greater than the thickness, is less than 10% of the total mass of raw materials;
• Group 2 - from 10% to 15%;
• Group 3 - from 15% to 25%;
• Group 4 - from 25% to 35%;
• Group 5 - from 35% to 50%.

Summing up, we will consider in which areas it is better to use gravel, and in which crushed stone.

What to choose

If we talk about what is better gravel or crushed stone, then first of all you need to decide for what purposes you plan to purchase raw materials. Despite the fact that both of these materials are obtained from rocks, they have quite significant differences.

For example:

• Thanks to its smooth shape and variety of colors, gravel becomes an excellent raw material for landscaping. Some of its varieties are suitable for the preparation of concrete mixtures, but only if you use construction, shungizite, glacial or washed gravel. However, even in this case, it will have a lower strength than crushed stone.
• Due to the fact that crushed stone is not mined naturally (as is the case with gravel), but by crushing rocks, the stones have an "unattractive" shape and look rough. However, due to its coarser grain size and better "adhesion", this material becomes an excellent aggregate for concrete mixes. Also, crushed stone interacts better with sand, cement and plasticizing additives.

As you can see, you need to choose gravel or crushed stone based on your wishes. Both types of raw materials are widely used in a wide variety of industries, are environmentally friendly materials and have excellent frost resistance.

One of the most needed building materials is crushed granite. It is a raw material of high strength, which depends on its fraction and specific gravity. The larger the variety, the more expensive it is. A product of one quality or another finds its application in various areas of construction. largely depend on: one can be more dense, the other - less dense.

Mining

It is found all over the place using the mining method. It is carried out from certain rocks that have a solid structure with a granular structure. Once upon a time, rocks from granite gradually arose due to the solidification of magma - volcanic lava thrown onto the surface of the Earth. Granite often has a pronounced reddish tint, and it is formed from quartz rocks, spar and varieties of mica. The stone from which crushed stone is most often produced is pink or gray, and its color is influenced by the content of other minerals in the rock.

Non-metallic materials are mined by blasting the rock with a certain amount of an explosive charge. First, drillers drill a hole of great depth in the rock, and then they leave explosives of several kg in it. Usually, several explosions are made, during which granite blocks appear, which can be re-exposed to explosives if they are very large. This type of production is called "overburden", in other words, performed by drilling methods.

After the blocks are divided into several parts, they are transported using special vehicles to the workshops, where they will be crushed and sorted into different fractions. In the process of sorting, large sizes are separated from small ones (crushed stone 5-20 mm, crushed stone 40 mm from larger stones). The cost of one cubic meter of crushed stone-bulk materials depends on the quality of the fraction.

Treatment

When crushing granite blocks, special mechanical equipment is used. Crushers, depending on the type of work and purposes, are rotary, centrifugal and jaw. Jaw crushing of rocks is the simplest method that requires minimal financial costs. The main components of such a mechanism are two plates or "cheeks", between which the lumps are crushed and worn out. In this case, one of the "cheeks" is in a stationary state, and the second swings, being set in motion by a mechanical drive.

Rotary crushing of granite rocks is the most popular method. A high-power motor is used here. Such installations can prepare all factions very well. As for crushing granite into other types (crushed stone with a fraction of 40 mm and more), in this case, a centrifugal shock installation is used. In addition to all these methods, at the present stage there are more portable, mobile mechanisms used in the place where the raw materials are mined.

Division into groups by factions

• Granite crushed stone of France 2-5 mm- this is the shallowest of. It is characterized by a high percentage of dust particles - up to 25%; among builders, it is not even considered a full-fledged stone. 5 mm and smaller is more of a processed product that occurs during screening of the base material.
• Granite crushed stone 5-20 mm... It is characterized by the absence of dust particles, or their insignificant content. One of those materials that are used quite often.
• Granite crushed stone 20-40 mm... This type is used in construction more often than others, there are no dust particles.
• Fraction 25-60 mm... This type of crushed stone is rarely used in construction. Low dust content.
• Crushed granite fraction 40-70 mm... The largest-caliber faction of all.

More about the fractional use of material

Crushed stones are often used as high-strength aggregates for concrete structures. Embankments in road construction require solid rock material, and a cuboid shape is best suited for this.

Screenings up to 5 mm (granite crushed stone of the finest fraction) is used for various types of decor, often such crumbs can be found when decorating garden and country paths, playgrounds and places for sports training. Since the screenings are crushed to sand, they are sprinkled on icy sidewalks in the icy conditions.

Crushed granite fr-tion from 5 mm also refers to small species, but it is more in demand compared to others. It is used to make admixtures for strengthening foundations and concrete structures.

Application crushed stone fr-tion 20-40 mm carried out during the construction of reinforced concrete structures and railways, when laying the foundations of the foundations. In addition, it is crushed stone of fraction 20 that serves as a filler in high quality concrete pavements, on which heavy construction equipment works.

Fractions of crushed granite 40-70 mm are used for the production of heavy concrete structures and when working with large quantities of it - for example, at large-scale railway construction sites and the laying of large highways.

Large fraction 25-60 mm used for the arrangement of the main railway lines. For arranging the embankments of spare rails, granite crushed stone of 5-20 mm friction is used.

The composition of crushed granite, its physical and mechanical properties

One of the key indicators on the basis of which one can judge the quality of crushed granite is the level of its homogeneity. The denser the granite crushed stone, the stronger it is, and the shrinkage over time is less.

It is also important to look at the content of various impurities in the form of clay, dust particles and other rocks, which do not differ in value and are unsuitable for modern construction. The cleaner the stone, the higher the adhesive characteristics of crushed granite in relation to the bonding materials. The purity of granite ensures its high resistance to radiation, and its resistance to low temperatures prevents premature destruction of the material.

The quality of crushed stone of friction 20 mm and its other varieties largely depends on the shape of its granular structure. This concept is called flakiness, or "flatness". If the crushing of the material has been done correctly, volumetric fractions are obtained in the form of a cube, which is the most optimal option for carrying out construction and road works. If the grains are flat or with sharp edges, they adhere weakly to each other, there are many voids between them (from 5 mm or more), and the density of any embankment decreases sharply.

The indicator of radioactivity indicates how much the material can emit radioactive substances or absorb them. The less this ability of crushed stone, the safer and better. In terms of resistance to radiation, it is considered one of the best materials. It is no coincidence that during the construction of nuclear power plants and other facilities that are radioactively hazardous, concrete structures are always used, which have an internal filling of high quality gravel.

The best indicator of the strength of crushed granite is 1400, the bulk density level is 1.4 tons per cubic meter, and resistance to low temperatures is 300 units.

Density of material

Often the meaning of the phrase "density of crushed granite" is not used quite correctly. What is density? Its indicator is measured in kg / m3 and is the same for both granite and crushed stone from it: 2600 kg / m3. To be more precise, we should talk about bulk density ... It is the bulk density that shows how much a cube of crushed stone weighs and the number of tons in a cube of granite, which is in its natural state (in other words, taking into account all the empty spaces in the granular structure of the stone). Thus, there is a direct dependence of the volumetric weight (how many tons of granite in a cube) on the density of crushed stone and its variety. The larger the fraction, the higher the density indicator.

If it is required to prepare a mortar from concrete, the density and composition must be taken into account when mixing. If the bulk density of crushed stone is high, then much lower costs for the volume of cement mortar will be required, which provides great savings in building materials. During transport and storage, the density level should also be considered. Knowing such indicators as the true density and bulk density of crushed granite will help to accurately calculate the carrying capacity of a vehicle for transportation, as well as what size storage space will be needed.

When crushed stone is produced, its density is at an average level, which must also be borne in mind when working with gravel.

Specific gravity

The specific gravity of granite crushed stone of fraction 20-40 mm is from 1.4 to 1.6 t / m3. All indicators must be looked at, taking into account such a property of crushed stone as flowability, therefore, the determination of the volumetric weight should be made only if the material is dry.

The specific gravity of crushed granite is the ratio of the raw material mass to the volume that it fills. Weight is measured in m3 (1m3 of crushed stone). This is important to consider when calculating the amount of material that is used in construction work.

Grade as an indicator of material strength

The strength of crushed stone is one of the most important criteria that is taken into account when carrying out construction work. In order to determine these indicators, a number of experiments were carried out, the essence of which was that the material was compressed in special containers. Compression is a simulation of the pressure that an asphalt roller exerts on it. The designation of the grade of the strength of the stone consists in the letter "M" and a certain number that follows after it. The higher the number, the greater the strength of the stone.

Consider a table describing the grades of crushed granite.

The number after the letter "M" also shows how much grain obtained from a weak rock is contained in a particular material. For example, rubble 200-300 contains no more than 15% of low-grade grain , 400, 600 and 800 - not more than 10% , and crushed stone of high strength grade 1000, 1200 and 1400 contains no more than 5% low-grained components .

Knowing the grades of crushed stone helps to understand what material is required to complete a particular task.

There is a generally accepted classification of its areas of application:

• M200 intended for use as a decoration and not suitable for global construction tasks.
• Strength M300 and M400 relatively low, but they can already be used to build simple concrete structures.
• Stamps 300 and 400 are in great demand among small wholesalers who build small objects.
• Medium-strength crushed stone M600, M800, and 1000 are used in the construction of roads with a low level of load and structures made of concrete of small size.

But the most demanded building material is brand crushed stone 1200 ... This is already a high-strength category based on granite. Crushed stone 1200 has not only a high strength index, it is resistant to moisture and low temperatures. Therefore, the brand 1200 and 1400 used for the construction of road surfaces that can withstand a high degree of stress, as well as for the manufacture of concrete structures that support bridges. High-strength materials are also used for the construction of runways and railroad embankments.

Interaction with other materials

Due to its roughness, granite crushed stone "seizes" well if it is used in the composition of the solution, which includes sand and cement. The composition becomes more homogeneous, so granite of a small fraction becomes a good filler. When concrete of different types is produced, different density of crushed stone and different fractions are needed. When mixing mortars, it is important to know that the greater the density of the crushed stone, the less cement consumption per mass will be.

When using such materials in different areas of construction, it never hurts to know what its varieties are (granite crushed stone of 20 mm fraction and others). It is not excluded that this knowledge can be very useful when building a country or country house.

The article presents the main characteristics of crushed stone as a building material. We will tell you about the difference between different types of crushed stone, what each of them is intended for. You will learn how to determine the main performance indicators (fraction, strength) depending on the purpose of the work.

The main parameter of crushed stone

Flakiness is the main indicator for crushed stone of any origin. It reflects the presence of relatively flat flat edges on individual stones. The larger such edges are in area, the higher the flakiness is considered. Grains with edges of a relatively large area have an acicular (acicular) or plate-like shape. Other grains (with conventionally the same edges) are called cuboid. The operational properties of the mass, especially in "dry" bulk form, depend on the percentage of such grains.

Crushed stone groups by grain shape

The ability to determine flakiness by eye will help when choosing crushed stone for your own needs. To do this, it is enough to know how this indicator affects the properties of the material:

1. Cuboid grains are better for compaction, resulting in a denser base. This is important when installing a foundation cushion and filling under the road. They are also the most durable (compared to other forms).
2. The spiky grains create voids in the mass of the stone. When creating a concrete structure, more mortar will be needed to prepare the mixture, and the compressive strength will be slightly lower.
3. At the same time, voids are useful for drainage. Providing sufficient packing density, crushed stone of the usual group removes atmospheric water.

Crushed stone characteristics

This material has two main performance indicators that you should be guided by when choosing for your own construction - frost resistance and strength.

Frost resistance

According to their resistance to freezing cycles, grains are divided into 3 categories. Marked with the letter F and a number indicating the number of freezing cycles:

1. Highly resistant. Brand F200, F300, F400. It is used for all types of critical structures, bridge supports, reinforced concrete products, high-rise construction, external dumps, offshore facilities and for the Far North.
2. Resistant. F150, F100, F50 brands. Used in construction in the southern regions and the Middle Strip.
3. Unstable. F50, F25, F15 brands. Introduced as bedding and drainage at a level below the GWL. Used for interior work and heated structures.

It should also be noted that laboratory studies of the frost resistance of crushed stone are carried out on a separate grain. In the structure (in concrete), the grain receives plus 30-40% to frost resistance due to the pressure inside the structure.

Strength

This most important indicator is determined by simulating the actual exploitation of the embankment - crushing, wear and crushing. Thus, the ability of the material to resist these influences is revealed.

Table of dependence of the field of application on the strength grade

The strength grade depends on the amount of admixture of weak rock in the mass of crushed stone. In this case, the prototype is subjected to a load of 20 MPa. Allowable content of weak rocks:

1. М1600 - less than 1%.
2. М1400 - М1000 - no more than 5%.
3. М800 - М400 - no more than 10%.
4. М300 - М200 - no more than 15%.

Rock with a weak rock content of more than 20% is called gravel and is used mainly for filling local roads, "change houses", creating temporary structures and other irresponsible work. It is quite acceptable to use washed gravel as crushed stone in private construction (except for foundations).

Varieties of rubble

Each of the items has its own classification by strength, size, frost resistance and other indicators. We will focus only on the practically useful aspects of the description.

Crushed gravel

This type of crushed stone is obtained by screening open pit rock and explosive mining of a stone rock. It is somewhat less durable than granite (limit grade M1200) and has an unsightly gray appearance. Moreover, its advantages are undeniable:

1. More quarries, competition.
2. The cost price is lower (due to the spread of raw materials).
3. Mining is easier (granite is harder than rock).
4. Extremely low radioactive background.

At the same time, the limiting grade and other properties of crushed gravel make it possible to use it for critical structures in all sectors of the national economy. There are four fractions of this material:

1. 3-10 mm - dropout.
2. 5-20 mm - "seed". They are used for small-piece products (paving slabs, etc.).
3. 5-40 mm - used for medium-sized factory products - concrete and well rings, curbs, lintels, etc.
4. 20-40 mm - the main material for the production of concrete and road filling.

Limestone (dolomite) crushed stone

Calcite carbonate (CaCO 3), compressed over time to a state close to a rock mass. According to the main parameters, it is identical to gravel. It is used for concrete products and road construction. A distinctive feature is white.

Granite crushed stone

It is obtained by blasting a granite massif, crushing and sieving the mass. In most cases, it has a red tint. The torn edges of the grains provide the best adhesion to the mortar. The shiny texture gives a good appearance to polished monolithic floors and other concrete products on crushed granite.

This type of crushed stone is recognized as the most demanded, because it has the highest strength. Accordingly, the enterprises offer the largest assortment of sieving fractions - from 0-5 mm to 70-120 mm. For each faction, there is a whole set of areas of application.

Crushed slag

This material is the result of crushing and screening of metallurgical dump slags and melts. Concrete products based on this crushed stone are 20-30% cheaper than conventional ones.

Secondary crushed stone GOST 25137-82

Material obtained from targeted processing of construction waste. It is produced in the same way as natural, only it is not a piece of rock that acts as a raw material, but a monolithic element. After the initial split, steel elements (reinforcement) are removed from it, then it is sent to the screen.

Such a material could save a lot of money: energy costs are up to 8 times lower, and the cost of concrete with such crushed stone is 25-30% less. On sale artificial crushed stone is 2 times cheaper than granite. Although its strength and frost resistance are inferior to natural ones (maximum M800 and F150), there are many areas of application for such indicators.

Having the necessary knowledge about the choice and advantages of different types of crushed stone, you can accurately determine its quality and acquire exactly what you need.