Building crushed stone: types, characteristics, use. Specifications and types of crushed stone

14.06.2019

Crushed stone is a loose building material of inorganic origin. It is obtained as a result of industrial processing of various rocks. When buying, the consumer is primarily interested in the fraction and breed. The price, purpose and scope of the material depend on this.

In the process of processing, crushed rock particles are sifted through special sieves (screens) and sorted by size and shape. A fraction is a range of sizes of individual grains, they are usually indicated in millimeters.

Conditionally divided into two groups:

1. Standard - dimensions in accordance with GOST.

2. Non-standard - parameters for special purposes, produced in agreement with the customer.

Screenings (granite chips) and various mixtures are also used in the construction industry. Within each species, a narrower classification of fractions is possible.

Dimensions	Fraction, mm	View
Standard	5-10	small
	5-20
	10-20
	20-40	average
	25-60	ballast
	20-70	large
	40-70	large
non-standard	10-15	small
	15-20	small
	70-120	BUT
	120-150
	150-300
Other	0-5	screening
	0-40	mixtures
	0-60
	0-80

Description of varieties

Depending on the raw material, several breeds are distinguished:

Granite - obtained as a result of undermining and crushing monolithic rocks. The grains can be gray, red or pink. The main advantages of crushed granite include increased strength, durability and lightweight processing. These characteristics are due to the content of quartz, mica and feldspar.
Gravel - mined by crushing. Another method is to screen large rocky debris in the quarry area. The main characteristics include a reduced level of radioactivity, moderate resistance to mechanical damage and affordable price.
Limestone is the result of industrial processing of sedimentary calcite rocks. Differs in ecological cleanliness, low density and excellent frost resistance. Due to the wide availability of raw materials and simple production technology, it is the cheapest of all types.
Slag - a product of processing waste from metallurgical, chemical enterprises, incineration solid fuel in boiler rooms. Crushed stone mass shows excellent characteristics of durability, tensile strength and mechanical shock. The rough surfaces of the grains provide increased adhesion to the binder component (cement).
Secondary - obtained after processing various construction waste: fragments of bricks, asphalt, concrete products.

Specifications and properties

1. Strength.

It is determined by the volume of inclusions of brittle rocks. Their content in durable grades of crushed stone should not exceed 5%. This indicator is of great importance in the construction of roads and railways, bridge supports, heavy foundations. In residential construction, the use of M800-M1200 is recommended.

2. Flakiness.

Classification according to the shape of the grains, the parameter shows the ratio of length to width and thickness of individual particles. It depends on the density of the concrete. The more cube-shaped grains in the crushed stone, the more evenly they are distributed in the solution and fill all the voids. The normal content is limited to the range of 15-85%. A high percentage of flakiness confirms the good drainage properties of concrete.

3. Frost resistance.

The number of complete freeze-thaw cycles is between F15 and F400. In the construction industry, F300 grades are usually used.

4. Adhesion.

The maximum degree of adhesion of binders with crushed stone particles is observed in gravel.

5. Class of radioactivity.

The indicator depends on the source of extraction of raw materials and is confirmed by GOST. In residential and industrial construction crushed stone of the 1st class of radioactivity is allowed, for road works - the 2nd.

Areas of use

1. Sifting - is selected as a filler when mixing concrete, masonry mortars, for the preparation of dry mixes, for the construction of footpaths, sports and playgrounds.

2. Road mixes - active use in the production of asphalt concrete, for laying the foundations of highways, runways, railway tracks, backfilling roadsides.

3. Small fractions are the most demanded types of bulk material. This the best way for concrete and casting of structures from it, laying the foundation, blind area, road works.

4. Medium - are used in the construction of industrial facilities, reinforced concrete structures, laying tram lines, roads and railways.

5. Large fractions - mainly in demand in the manufacture of large volumes of concrete. Also selected as a drainage, in the construction of urban roads and foundations for them.

6. BUT (building stone) - sometimes selected for laying massive foundations or strengthening coastline. Main application as decorative elements at finishing of protections, reservoirs, pools. Waste after crushing can be used as a concrete aggregate.

Crushed stone 25-60 is purchased for laying the ballast layer of the railway track. Narrower fractions (5-10, 5-15, 10-15, 15-20) are in demand in the production of asphalt concrete, processing various surfaces, patching, the device of a blind area around buildings.

Purpose

For concrete - it is recommended to use gravel, granite or limestone fine crushed stone as a filler. Small particle sizes ensure minimal porosity and excellent product strength. In the production of medium and heavy concrete, it is better to choose a slag mass.

For the foundation - in most cases, gravel is used, the main properties of which are strength and affordable price. When building multi-storey buildings or massive objects, it is better to choose crushed granite. When constructing lightweight buildings (arbor, garage, shed), cheap limestone material is suitable. Optimal fractions for bookmarking: 5-20 and 20-40.

For drainage - rubble stone is the most suitable. It is resistant to moisture, temperature changes and soil acidity. When using standard species, it is better to select large fractions. In order to save money, you can buy recycled materials. Despite the low price, they have all the properties of primary crushed stone.

For blind area - the best choice will be gravel with a particle size of 5 to 40 mm.

Price overview of popular factions

rubble	Price *, rub./m3
	5-20	20-40	40-70
gravel	1580-3000	1530-2850
granite	1850-3300	1600-3100	1700-3070
Limestone	1100-2700	1170-2500	1170-2500
slag	1000-1500	800-1200	800-1200
secondary concrete	1020-1250	800-1000	800-1000

* The table shows the cost with delivery in Moscow.

For the manufacture of concrete elements of small thickness, it is better to use crushed stone with a grain size of up to 10 mm. By production of massive products it is possible to apply 10-20 and above.

Before you buy gravel of a certain fraction, you need to require a passport. A conscientious manufacturer always lists the main features, characteristics and applications.

In an attempt to save money, some customers seek to purchase cheap material with low flakiness characteristics. Most of it is made up of needle-like or lamellar grains. Such a choice is justified if it is intended for filling footpaths, playgrounds, decorative works or drainage system. When it comes to laying a foundation or blind area, it is better to buy crushed stone with the maximum flakiness. Otherwise, you will have to spend extra on sand and cement, which in the end is much more expensive.

Recycled gravel allows the developer to reduce costs by 35-50%. This helps to solve the problem of waste disposal. V construction work it is possible to use not only individual fractions of recycled material, but also non-fractional with a grain size of 0-70 mm.

Crushed stone is construction material, which has a granular structure. To obtain it, unlimited rocks are used, which are subjected to fine grinding. Given the characteristic natural material in industry, they can mine this type: limestone and granite. During the processing of waste, secondary and slag can be obtained. All of these varieties of natural material are actively used in the field of construction.

What can be

The assessment of the presented material is most often given on the basis of its fractional composition. It provides for the required range of dimensions for its individual granules. The essence of such events is that when using a special sieve, it is possible to sift crushed stone.

Scope of use

Consider the areas of use of such natural material as granite, taking into account its fraction:

In addition to crushed stone obtained from granite, there are other material options, each of which has its own areas of use. For example, granite chips can be used in the production paving slabs, concrete floors or as finishing of interiors and facades. Such material is used in the creation of sports grounds, children's territories, and the well-known unique properties of granite chips in the fight against ice.

About what weight of crushed stone fraction 20 40 in 1 m3 can be found from this

The next type of crushed stone - gravel, can boast of its high rates strength and frost resistance. It is used as a filler for concrete and reinforced concrete products, in the arrangement of sites and paths. Such material is divided into fractions as follows: 5-20 mm, 20-40 mm, 40-70 mm.

You can find out what the flakiness of rubble is by reading this

Derived from limestone, is considered the most popular. His characteristic feature is a low price. The material contains calcium carbonate. It can have such a color: yellow, red, brown. It all depends on the amount of impurities in the composition.

The video tells how many tons of rubble are in a cube, specific gravity:

About what is the proportion of concrete and how much rubble in it describes this

Such material has been actively used in the national economy in the production of mineral fertilizers, soda. It is also used to prepare Portland cement, to purify beet juice. According to the standard, such crushed stone has fractions as follows: 5-20mm; 20-40mm; 40-70 mm.

For carrying out various construction activities, it is necessary to use crushed stone of secondary manufacture. This product is characterized low price, however, its quality characteristics are not inferior to the primary material.

In the photo - a table of crushed stone weight:

The main thing is that his faction should be of medium size and with low level flakiness. Thanks to these indicators, it is possible to obtain a strong adhesion to the concrete mortar. The use of secondary crushed stone leads to a 1.5-fold reduction in the cost of construction activities and allows solving the issue of construction waste disposal. In the field of construction, individual fractions of recycled material or a non-fractional product with a grain size of 0-70 mm can be involved.

You can find out how much a cube of crushed stone weighs from this

Obtained from slag, it has found its application as a cement concrete filler for thermal insulation of bases in the field of road construction, as well as during the arrangement of asphalt concrete pavements. Slag material may have graying fractions: 5-10mm, 10-20mm, 20-40mm, 40-70mm, 70-120

Table 1 - The area of use of crushed stone of a specific fraction

Fraction of rubble	Engagement area
5 (3) ÷ 20 mm;	The process of manufacturing concrete, concrete and reinforced concrete products, elements of bridges, floor slabs.
20 ÷ 40 mm; 40 ÷ 80 (70) mm.	Foundation construction, construction of industrial facilities, production of concrete, concrete and reinforced concrete products, construction of roads for cars and trains.
Combined application of several fractions with particles from 20 to 70 mm	The erection of powerful industrial buildings and structures.
70 (80) ÷ 120 mm, 120 ÷ 150, over 150	Construction of powerful foundations, industrial buildings, use in landscape design: for finishing and decoration of pools, reservoirs.

Crushed stone is a very popular building material today. It is actively used in various sectors of construction. Due to the presence of different fractions, this material has different indicators of strength and frost resistance. Based on this, each person will be able to choose the appropriate type of material for specific tasks.

Gravel crushed stone is obtained in two ways: crushing into smaller parts of monolithic rock or by sifting other quarry rocks. The material is widely distributed and is being mined on a large scale.

general information

Crushed gravel is classified as a non-metallic rock, it is inorganic, has a more rounded surface, unlike, for example, granite.

The material is considered very environmentally friendly, although it is still inferior in strength to crushed gravel. But at the same time, its price is lower, provided that other indicators remain high. This is what determines the use of this breed in the construction of a large number of objects.

A little more about what crushed stone is on the video:

Specifications

Crushed stone of this type not only has good qualities, but also meets a number of important characteristics according to GOST 8267 93:

Rock strength M800 - M1000;

Flakiness (shape of particles) - 7 - 17%. One of the most important features. The most preferred shape is cuboidal because the flat particles will not fit snugly together. This allows you to reduce the density of the embankment;

Density - 2400 m / kg3;

Frost resistance F150. Perfectly tolerates up to 150 periods of thawing and freezing;

1 class of radioactivity. This means that crushed gravel is not only unable to radiate it, but also absorb it. This characteristic is an order of magnitude higher than that of the granite type of crushed stone;

Weak breeds are 1.5% or less;

Do not have foreign harmful impurities;

Clay and other dust-like particles occupy only 0.6% of the total strength. This allows us to talk about the best susceptibility to binder materials;

The bulk density of different fractions, as a rule, does not differ. Usually it is about 1.3 tons, but maybe less, since this characteristic will depend on the origin or place of its extraction.

Extraction of crushed gravel in quarries

Gravel crushed stone is mined together with other types of stones in loose sedimentary rock. Since initially it is a monolithic rock, blasting work will be required.

When a series of explosions is carried out by specialists, the rubble will break into relatively small blocks. Then they are placed in a special crushing technique, which allows you to grind the stone into the required fractions.

As soon as the crushed stone is crushed, it is sieved. This is done by screening, which allows you to separate smaller rocks from large ones. Almost immediately, it can be used for various purposes, including construction.

Brands and types of crushed gravel

Usually crushed stone of this type is divided into different types, and it will depend on what strength it has. There is a division into high-strength (M1200), strong (M1000), medium (M800), having weak strength (M600), as well as the weakest strength (M200).

Fractions of rubble

Gravel crushed stone is divided into fractions. Each of them is used for some main purpose.

There is the following division:

up to 5 mm. Gravel screening is usually used to prevent ice or landscaping, as it is very shallow;

up to 10 mm. The main use is concrete production, landscaping, foundation construction;

up to 20 mm. Is the most in demand. The main use is the production of cement, products from it, the construction of a foundation;

up to 40 mm. The main use, as in other cases, is foundation work, the production of concrete, products from it. Additionally required for drainage work;

up to 70 or up to 90 mm. Necessary both for previous purposes and for decorative purposes. Widely applicable in road construction;

up to 150 mm. This faction has its own name - BUT. Very rare view, is used for decorative purposes, as well as the main material for finishing ponds, pools, drains or river banks.

In the photo, various fractions of gravel rubble

Application

Gravel crushed stone has found wide application in many areas, including the following:

Manufacture of sleepers from reinforced concrete, as well as other structures from this material;

soil drainage;

Concrete production;

Floor slabs;

Road construction;

Artistic concrete casting;

As a leveling material for other monolithic backfills;

For landscaping and garden paths;

Construction of bridges and other massive structures.

Also, the rock can be used as a bulk layer on railways, at airports, as well as during the construction of radioactive facilities. In the latter case, the use of crushed gravel is strongly recommended, since it has very low radioactivity.

Depends on the features and height of the future building. In most cases, crushed gravel is used for cushioning and preparing concrete.

Pros and cons

This type of material has both negative and positive sides. The first can be attributed to the fact that its strength is lower than that of crushed granite.

However, there will still be more pluses, since crushed gravel has both an affordable price and other very outstanding characteristics. This includes resistance to radiation, and breadth of application, and environmental friendliness.

Based on all the information about crushed gravel, the following estimates can be made for the material:

The price is 5 points. It is much more affordable than its granite counterpart, while maintaining fairly high performance;

Practicality - 5 points. The use of this material is possible in many areas, from the production of concrete to the construction of structures;

Appearance - 4 points. Both wide and fine fractions of the rock are widely used for decorative purposes;

Ease of manufacture - 4 points. Of course, it is impossible to extract it on your own, but quarry mining is a rather complicated process;

Laboriousness when using - 5 points. Does not require any additional processing and can be used immediately after purchase;

Environmental friendliness - 5 points. It has no harmful impurities, and the origin of the material is completely natural.

Any construction process requires the right selection of materials. This is done during the design of the building. If not carried out correct calculations– it may have insufficient performance characteristics. It is especially important to understand what kind of crushed stone is needed in order for the concrete strength characteristics to meet the necessary ones - a prerequisite for achieving design indicators. Next, we will talk about what types of crushed stone are and how to choose it, based on the fraction and GOST standards.

Crushed stone is a rock crushed by special equipment into elements of a certain fraction. This process can be done at the place of production or in the conditions of enterprises. The manufacture of crushed stone is not considered particularly difficult, but requires compliance with the standards that govern GOST.

If we talk about its production, it is produced in several steps:

Loading stone into containers, from which they fall on crushing equipment.
Splitting up.
Distribution into fractions and brands, depending on the size.

Sorting of crushed stone depending on the size of the elements of the detailed stone rock - especially important process. To comply with it, GOST 8267-93 and 8269-87 were created.

Types and characteristics

To create high-quality concrete, you need to be well versed in the characteristics of crushed stone. He has different features and an understanding of what its type is needed in a particular situation affects the success of the construction process. Technical specifications:

frost resistance level. The duration of the preservation of the original structure depends on this indicator, without the influence of freezing and thawing on it. The indicator of frost resistance is important in conditions of frequent decrease and growth of the column on the thermometer. The letter F is used to designate this parameter. The numbers after it are the number of cycles. Granite crushed stone has the highest frost resistance: about 300-400 cycles.
Flakiness. The parameter denotes the percentage of elements with smooth surface among the total. The larger it is, the worse the particles adhere and the level of concrete strength will be lower. According to this indicator, crushed stone is divided into 5 groups. Of these, the best is the cube-shaped grain.
Density. The greater the mass per unit volume, the higher the level of this parameter.
radioactive radiation. Depending on the level of radiation, the scope of crushed stone is determined (1-3). The first is suitable for the construction of residential buildings, and the third is exclusively for road construction.
strength level. This parameter determines the load force that the material can withstand without changing its structure (deformation). This is important when creating concrete with the highest strength characteristics.

The listed parameters are of great importance, but when choosing crushed stone, the main attention is paid precisely to the size of its fraction. Depending on this indicator, the scope of the material is determined. Crushed stone is of such fractions:

0 by 5 mm. This faction is rightly called the smallest. Apply for finishing works, for decorative purposes and landscaping. Sometimes used to sprinkle slippery surfaces.
3x8, 5x10, 10x20mm. Small but most popular faction. It is used to create mortar, structural elements and concrete.
20 by 40 mm. This fraction is called the middle. It is used to create concrete, pillows for the foundation of parking lots, roads, buildings, as well as temporary coverage of areas where large-sized equipment works.
25 by 60, 40 by 70 mm. Large fraction of rubble. Used to create the foundations of buildings with large dimensions, as well as large structures made of concrete.
40 by 200 mm. This faction is called but. It is a piece of rock formed as a result of an explosion. Used for decorative purposes or for filling concrete in especially large quantities.

As is clear from the above, the best option for creating concrete mix- small gravel. But sometimes they order the manufacture of a filler, one of the sides of which can exceed 300 (30 cm).

Grades of rubble

Another important parameter when choosing is the grade of crushed stone. It is influenced by strength indicators, which are taken on the basis of the level of crushability, abrasion during experiments, as well as compressive strength. Strength indicators are mainly affected by the structure of the rock, which was crushed to obtain crushed stone. Crushed stone has the following marking:

M1200, 1300, 1400. The content of elements of an insufficient level of crushability (weak particles) is less than 5%.
M800, 900, 1000, 1200. Less than 10% of particles of weak crushability.
M600, 700, 800. Grains of weak crushability are also less than 10%, but the strength of the bulk of the material is lower.
M200, 300, 400, 500, 600. Particles of insufficient strength with crushability up to 15%. Obtained after crushing weak stone rocks.

The highest marking rate is M1200-1400. It is obtained by granite crushed stone, which has maximum strength indicators. For the construction of the foundations of one-story buildings, it is enough to use crushed stone of grade 600.

Also, the brand can be found from the table of bulk density of particles of materials according to GOST.


Brand	Density in kg/cu.m.
250	Less than 250
300	250 to 300
350	300 to 350
400	350 to 400
450	400 to 450
500	450 to 500
600	500 to 600
700	600 to 700
800	700 to 800
900	800 to 900
1000	900 to 1000
1100	1000 to 1100

Tab. Crushed stone grades by density (bulk)

From the above, it becomes clear that you need to choose crushed stone based on the level of strength, crushability, abrasion, the size of the elements of the bulk, frost resistance, the percentage of weak particles, etc.

How to choose crushed stone for concrete?

In order to determine what kind of crushed stone is needed to create the optimal concrete solution, it is worth referring to the requirements of GOST. It is worth considering that high-quality concrete may contain several fractions - this increases the density of the structure. For example, if the indicator of the largest allowable size of the filler elements is known, you can see in the table the list of fractions that can be used (GOST 8267-93).

Max allowable grain size	Fraction of coarse aggregate
10 mm	5 by 10 or 3 by 10
20 mm	5(3) for 10 and 10 for 20
40 mm	5 (3) by 10, 10 by 20 and 20 by 40
80 mm	5 (3) by 10, 10 by 20, 20 by 40, 40 by 80
120 mm	5 (3) by 10, 10 by 20, 20 by 40, 40 by 80, 80 by 120

It should be borne in mind that according to GOST for laying the foundation optimal size crushed stone elements: 40 to 80, and a grain of a smaller fraction is used to prepare the solution.

Granite crushed stone

Such a filler can be considered the most common in construction. It reaches the greatest strength and, according to GOST, its marking reaches M1400, and never drops to M300. It also has the highest crushing complexity. It is a representative of non-metallic rocks and is a petrified lava in the bowels of the earth's crust. Therefore, among other types of crushed stone, it has the highest rates of resistance to temperatures (about 300 cycles) and water resistance. Concrete with the highest strength is made from it. Granite crushed stone - the best option for creating concrete structure and bases, which, according to GOST, must have maximum indicators of stability and durability.

Crushed limestone

This type of fossil, although it does not have the best performance, but is the most accessible. It is used for the production of reinforced concrete blocks and in the construction of transport routes. It is also used for landscaping - allows the cost and environmental performance. The simplicity of its crushability reduces the price of limestone stone.

To produce concrete of optimal quality, it is necessary to soberly assess the loads on the bases and products. Based on the data obtained, the size of the crushed stone fractions is selected. When making a choice, do not neglect the requirements of GOST. If you ignore the rules and use, for example, grade 300 crushed stone to create the base of a multi-storey building, unpleasant consequences are possible. Pay attention to all crushing characteristics, fillers (including their structure), level of temperature resistance, particle size, as well as the performance of cement and even water. Only in this way is it possible to create foundations and structures with proper operational characteristics capable of serving for decades.

What are the brands and types of gravel? updated: February 26, 2018 by: zoomfund

Read on topic

Crushed stone is a material widely used in construction, it is obtained by crushing rocks. It is classified according to the following features:

The sources from which it is extracted are granite, lime, gravel, quartzite, as well as the so-called secondary or artificial crushed stone obtained by crushing construction waste.
Stability to loads - this indicator depends on where a particular type will be used. There are several degrees of strength, which are determined in special devices by compressing crushed stone hydraulic press in dry or wet condition. The most durable is crushed granite, capable of withstanding heavy loads, lime crushed stone has the least strength.
Frost resistance is characterized by the number of freeze / thaw cycles maintained by a certain type of crushed stone while maintaining its main qualities. Marked with the letter "F".
The size of the fractions, or grains during crushing. The main sizes used vary from 5 to 70 mm, smaller or larger fractions of these parameters can be used in decorating landscapes.

The crushed stone used in construction is divided into categories, each of which has its own characteristics and properties necessary for a particular type of work. It depends on the origin of the material, and includes the following types:

Granite. When crushing granite layers, an especially strong crushed stone is obtained, which has excellent moisture and frost resistance, which makes it indispensable for the production of particularly critical work, for example, for pavement airports and cosmodromes, as well as in the ballasting of the railway track. The disadvantages of such rubble are the high cost and natural radioactivity.
gravel. Gravel to obtain this type of crushed stone is mined in quarries or reservoirs for subsequent crushing. In terms of strength, it is inferior to granite rubble, in terms of other characteristics it meets all the requirements for responsible construction.
Limestone. Sedimentary rock mined is used for production open way. This type of crushed stone is the least durable, but it is very resistant to frost. It is used for the manufacture of some low-strength concrete grades, in private construction, the construction of small structures, as well as filters for mechanical cleaning.
Artificial. It is also secondary or slag, obtained as a result of processing construction waste, a medium-strength material used in all construction areas. The advantages are low cost and the possibility of crushing into fractions of any size.
Diabase. Diabase is an outflowing volcanic rock, crushing which produces high-strength frost-resistant crushed stone, which is used for the construction of especially busy highways and high-quality reinforced concrete products. Diabase is environmentally friendly, resistant to temperature changes and complies with radiation safety standards.
Basaltic. Dense basalt rock is stronger than diabase, but is somewhat brittle. Crushed stone from it is used for the production of facing slabs, road surfaces and filling heavy concrete.
Porphyrite. Mined using special equipment in porphyrite quarries, porphyrite crushed stone has low radioactivity and high moisture resistance. It is used for works of small volume - wall materials, fine-grained reinforced concrete.
Gneiss. The rock from which crushed stone is made is characterized by its friability, due to the composition of quartz and feldspar. Gneiss crushed stone is mainly used for paving roads, but is subject to weathering.

The value of this important characteristic lies in the shape of the grains and their content in the total mass of crushed stone. Grains are lamellar, when their length exceeds the thickness by 3 or more times, needlelike ones have a length that is 3 or more times greater than the width. There are 5 categories depending on this feature:

1 - cube-shaped crushed stone, up to 10%,
2 - improved crushed stone, 10-15%,
3 - regular, 15-25%,
4 - regular, 25-35%,
5 - normal, 35-50%.

The lowest flakiness values are considered the best for the production of concrete used in building structures, due to the cubic shape of the grains with the lowest percentage.

However, significant financial expenses for the production of cube-shaped crushed stone, as high-quality crushing equipment is required. This will significantly reduce production volumes. Cuboid crushed stone is used for filling upper layers road surfaces and production of concrete for critical construction projects.

The shape of the grains has a significant impact on the adhesion of crushed stone with mortars, that is, on adhesion, which makes the erected structures durable.

Crushing of hard rocks for the production of crushed stone is different sizes its fractions, which comply with the standards of GOST. These are 5-10, 10-20, 20-40 and 40-70 mm. The most suitable for construction are mixtures of several sizes, which reduce the voidness, and therefore the amount of required cement mortar. At the same time, the strength of the object under construction increases.

The presence of impurities in crushed stone, such as dust, clay or silt, adversely affects the quality of concrete, so the crushed stone is cleaned before use.

Areas of application of crushed stone

Foundations. In most cases, crushed gravel is used to build foundations; it is quite durable and inexpensive compared to granite. However, when laying the foundation for a large, complex object, in particular, for a residential building, crushed granite is preferable. Light buildings such as a garage or a barn can have a base even with crushed limestone, which has the advantage over other fillers - a low background radiation.

The acceptable value of fractions used for foundations is 5-20 mm or 20-40 mm.

Backfill. The construction process often requires raising the soil, the so-called dumping. The material for this event is crushed stone of different fractions.

The largest fractions - rubble stone - are used most often, because they have increased natural resistance to external influences, such as sudden changes in temperature or acidic soils. The heterogeneous size of the stones, the alternation of their obtuse and sharp corners prevent subsidence even in harsh climates.

The use of fractions standard sizes perhaps, if we take only the largest of them, since the strength of the backfill depends on this. A crushed stone pillow is usually used at an average level of groundwater.

The use of screenings as a cushion is undesirable, although it has an attractive low cost. Dust and fragments that make up screenings are not suitable here. But this material is perfect for giving, subject to stable soil that protects against melt water. Over time, the pillow can sag due to the washing out of dust with water, which will lead to the formation of cracks.

Harmful impurities

One of the important requirements for crushed stone is resistance to chemical reactions with the alkaline environment of cement. Crushed stone should not contain substances that cause corrosion of reinforcement and embedded parts.

The strength of concrete is reduced by: clay, coal, acid, oil shale, asbestos. Due to the tendency to weathering, the presence of apatites, chlorites and phosphorites is undesirable.