When starting construction work using concrete mixtures, it is necessary to clearly understand what fraction of crushed stone is needed for concrete. The solution filler is largest share volume, therefore crushed stone is no less important than cement for determining the quality of concrete. The durability and strength of concrete depends on crushed stone; it determines the plasticity of the solution, reduces shrinkage and cement consumption, reducing the cost of work.
Concrete crushed stone is selected based on the problems solved during construction and operation ready-made structures made of concrete. The pressure to which a concrete path is exposed differs many times from the load on the foundation of the building. Just as the conditions for the foundations of light buildings differ from the requirements for foundations multi-storey buildings. And although many factors influence the choice of crushed stone for concrete, there are certain rules that must be followed.
For pouring the foundation for construction large structure a mixture of small fractions of 5 - 20 or 5 - 10 mm granite crushed stone is used. Cuboid-shaped grains are well compacted among themselves. A large grain of 20 mm gives strength to the solution, and smaller grains of 5 mm or more fill the voids between the large ones, forming a dense mass. Such concrete has good strength and frost resistance, but increases cement consumption.
Suitable for foundations for small buildings crushed gravel middle fraction 20-40 mm. A solution with a medium grain size is less plastic and is harder to compact and reinforce, but has a margin of safety and a low price.
For concrete floors, paths, blind areas, paving slabs, limestone and secondary species crushed stone with grain of fine fractions and increased flakiness. Crushed stone with a lamellar grain shape increases cement consumption and is difficult to compact, but is the most economical.
Using crushed stone from rocks standardized by GOST 8267, from metallurgical slag by GOST 5578, and from thermal power plant slag by GOST 26644.
Since concrete gains strength over six months or more, the strength of crushed stone to guarantee reliability is taken three to five grades higher.
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Concrete strength grade |
Crushed stone strength grade |
Crushed gravel is slightly inferior in characteristics, but cheaper than granite, and is classified as M800 – M1000 and F200. It is used both independently and in a mixture with granite to reduce the cost of construction.
Both types of crushed stone are used for the manufacture heavy concrete. Limestone, recycled and slag are used to produce lightweight concrete.
The shape of crushed stone grains affects the quality of concrete; the more it resembles a cube, the denser it will fit into a given volume and the greater its strength. The lamellar and needle-shaped grains form a loose solution, are less durable and are less compacted.
In concrete solutions, crushed stone with a grain size from 5 to 70 mm is used. How finer crushed stone, the higher its cost, since it requires high production costs.
To fill the foundations for individual cottages, small fractions of crushed stone 3–8 mm are often used; 5 – 10 mm; 10 – 20 mm and 5 – 20 mm. They are used both alone and for economy, mixed with medium fractions. For pouring a reinforced belt, preference is also given to small fractions of 5 - 10 mm and 10 - 20 mm. The smallest formwork size rarely reaches 35 cm and the middle fractions fill worse reinforced belts and form many voids.
Crushed stone of medium fraction 20 - 40 mm is used in the foundations of houses, floors, the manufacture of beams, floors, and load-bearing structures. It is used both in private construction and for the construction industrial facilities.
Large fractions of crushed stone 25-60 mm; 20-70 mm; 40–70 mm is used for large volumes concrete works during the construction of multi-storey buildings. And it is used in a mixture with crushed stone of medium and small fractions. For individual houses, this fraction is almost never used.
Crushed stone is a bulk building material inorganic basis with different sizes of fractions (grains). It is most often used as a non-binding filler in concrete, which allows future structures and their foundations to withstand operational stresses. Crushed stone is added to the solution both to reduce its cost and to give it strength and elasticity after hardening, reducing shrinkage and the risk of deformation.
The material is obtained by crushing rocks or industrial waste, as a result - the stones have different shapes and remain rough, which increases their adhesion to cement and sand. For fraction size crushed concrete influences the maximum value individual elements, it is appropriately labeled, which makes selection and purchase easier. Depending on this, the solution acquires certain properties, in particular - the addition of large rock increases the strength during setting, and small stones - density (promotes better filling of voids).
This material is classified according to several criteria: the type of raw materials used, the size and shape of crushed particles, frost resistance and strength. Crushed stone is made from hard granite, metallurgical and construction slag, gravel and limestone rocks. The stronger the raw materials, the stronger the loads the future structure can withstand. Eg, the best option granite will be used for pouring the foundation, and gravel will be optimal in terms of price and quality. Depending on the shape of the crushed stone fractions and their percentage in the total mass, three types of mixtures are distinguished:
But the main indicator that determines the properties of crushed stone for concrete remains the size of the fractions. The standard ones include: from 3 to 8 mm (eurocrushed stone), 5–20, 10–20, 20–40, 25–60, 20–70, 40–70. Crushed stone with fractions from 5 to 10, 10–15, 15–20, 70–120, 100–300 is considered non-standard. How smaller size, the more expensive the building material, this is due to the complexity technological process when crushing it and more thoroughly sifting. In some cases, it is possible to mix a coarse fraction of crushed stone and small stone chips, the latter being used as an accompanying filler.
The most popular sizes are 20–40 mm, this is due to the low cost of this brand, but for pouring a foundation or when high requirements for the strength of concrete, it is better to buy backfill with grains from 5 to 10 mm or 5–20.
Markings
Depending on the frost resistance of the material, they are distinguished: F15, F25, F50, F100, F150, F200, F300, F400. The grade is not related to the size of the crushed stone fraction and is determined by the number of cycles of thawing or defrosting or saturation and drying in a solution of sodium sulfate. For mixing concrete, the optimal frost resistance is 300 or more (this is sufficient for pouring foundations and frequently used external structures). This indicator must be written down in the crushed stone passport, as well as the size of the fractions.
The main marking implies strength source material during compression, crushability when crushing rock and the degree of wear during grinding in a drum. The indicator indicates the resistance of concrete external influences like the weight of a vehicle or the load on a foundation. The high-strength grades of crushed stone are M1200–1400, the very weak are M200, the norm is the percentage of grains obtained from weak rocks (when compressed in a water-saturated state to 20 MPa). For comparison, in the M300 this figure exceeds 15%, in the M1400 - no more than 5.
The ratio of crushed stone and concrete grades
The strength of the solution is determined by its fillers, the characteristics of which are indicated in the attached instructions or on the packaging. In practice, this means that M400 cement will not produce M500 or higher concrete; the corresponding ratio of grades is presented in the table:
Determining the strength of concrete depending on the fraction of crushed stone is approximate, but deviations are allowed. The latter are regulated by changing the ratio of sand or cement, adding granite chips. But in general, to obtain the required grade, it is important to observe strict proportions of the solution. Before choosing what crushed stone is needed for concrete, it is recommended to determine the intended purpose of the structure and calculate future loads. For a solution up to M250, gravel is sufficient; the use of non-standard sizes grains High-strength grades (M300 and more) require the addition of granite screenings, preferably with square fractions up to 20.
According to building codes, the content of crushed stone with increased coarseness in the mixture varies from 1 to 20%, and undersized crushed stone should be within 20% of the total mass. If crushed stone with a fraction of up to 20 mm is used for concrete, problems with the distribution of voids do not arise. When this indicator increases to 40 mm, another type of filler (with different, smaller grain sizes) should be added to the solution. Accordingly, choosing a filler with a grain size of up to 70 mm implies adding at least three different options crushed stone fractions. The size cannot be less than 2/3 of the distance between the longitudinal reinforcement, but no more than 30% of smallest element building structure.
Examples of using
Fine-grained mixtures are needed in the manufacture decorative items made of concrete, artificial stone, paving slabs, it is also added to the composition for asphalt or other road surfaces. The use of too fine filler for pouring foundations and structures load-bearing walls not economically feasible, plus the risk of shrinkage and deformation increases. The medium and most popular crushed stone fraction (20–40 and 10–20) is better suited for creating large and small concrete structures. This perfect option for pouring the foundation. For cooking quality solution A concrete mixer should be used, it is difficult to achieve uniformity when mixing crushed stone, sand and binder cement manually.
Material with a fraction from 40 to 70 is classified as coarse-grain, and is needed when constructing massive buildings and mixing concrete in large volumes. It is better not to add it to solutions when pouring the foundation without adding auxiliary fillers of other sizes. Such material is difficult to obtain, the required quantity is calculated in advance, and its delivery is ordered separately. Crushed stone with a coarse fraction of 100 mm or more is called rubble or building stone; it is used mainly for decorative purposes, and not for preparing concrete. The same applies to fine granite chips, but the latter is indispensable when creating self-leveling floors and as an auxiliary additive.
Particular attention is paid to the choice of filler when making mortar for pouring the foundation. The base can withstand maximum loads, therefore, for this type of work, concrete with a strength of at least M300 is required. Accordingly, a granite filler of at least M1200 is needed, although the addition of gravel is allowed for country houses. Recommended fractions of crushed stone for the foundation: 5–10, 10–20, 20–40, it is advisable to buy grades with a square grain shape.
IN concrete mixture includes several components that allow you to give it everything required characteristics. It must contain 3 main components: cement, water and aggregate. Very often crushed stone is used as a filler because it has high performance characteristics.
To obtain high-strength concrete, high-strength types of crushed stone are used.
The strength of crushed stone can be 1000 MPa or even more. This value will depend on the type of material and its characteristics. Therefore, let’s consider what crushed stone can be used to prepare a concrete mixture.
Types of crushed stone: a) cube-shaped; b) acute-angled; c) wedge-shaped; d) flaky.
Crushed stone for concrete can be artificial and natural. The first option is obtained from construction waste and household slag. It is a recycled material, so it has a low cost. IN construction work it is almost never used (it is used to strengthen weak soils in places where non-federal roads are being built). The second type is obtained from rocks by crushing them. With the help of crushed stone you can reduce creep and shrinkage of soil, increase the strength and durability of concrete.
The choice of crushed stone is carried out according to such characteristics as the size of the fractions (the size of individual particles that predominate in the composition of the material). The smaller the fraction size, the smaller its number will be.
When coarse-grained crushed stone is used to ensure high strength when setting concrete, and fine-grained crushed stone is used to better fill voids and cavities.
Needled and flat crushed stone reduces the strength of the mixture, while increasing cement consumption. Its use reduces the frost resistance of concrete, so when carrying out construction work, crushed stone of this form is avoided. Let's take a closer look at each type of crushed stone that is used in construction work.
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Granite crushed stone for concrete
This material is one of the most durable ore materials. It is made by crushing natural granite. Such crushed stone is the best filler for concrete, which should have a high grade:
- airfield and road surfaces;
- critical areas that are under heavy load (columns, walls, slabs);
- bridge deck and other types of bridge structures.
The quality of granite crushed stone can be determined by such characteristics as density, compressive strength and fraction, which should be in the range of 5-150 mm. The fraction with a size of 5-20 mm is in highest demand, which is used for the construction of reinforced concrete products, bridges and road surfaces. When used, the reliability of the composition and its high performance parameters are guaranteed.
The average fraction has dimensions of about 40 mm, which is used in the construction of industrial facilities. The size of the coarse fraction required for the construction of large structures is 40-70 mm. Larger dimensions are used in the construction of rubble concrete foundations.
Granite material is quite durable in its performance characteristics. Its grade is in the range of 1200-1400, and frost resistance is up to 400 cycles.
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Gravel and limestone material
Crushed gravel is obtained by sifting quarry rock or by crushing natural rocks. In terms of performance characteristics, it is inferior to granite, but has more low price. This filler is widely used in the production of reinforced concrete products, in road construction and in the construction of foundations. Depending on the size of the fractions, it is divided into small (up to 10 mm), medium (10-20 mm) and large (up to 40 mm).
Crushed stone made from limestone is one of the cheapest types. According to the accuracy class, several groups of such material are distinguished:
- grade M600-M800 is the result of processing limestone or dolomite. She has high performance and has big size factions;
- grade M300-M600 is made of limestone;
- grade M200 is almost never used for the production of concrete, as it has a high price.
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Dependence of concrete grade on crushed stone grade
Any hard rock is suitable as the main filler: expanded clay, limestone, gravel, granite, asphalt or crushed brick. But there are some nuances here. Each filler has a certain strength, which leads to severe restrictions on the possibility of application. For example, the manufacture of a critical structure is unthinkable using broken bricks.
The durability of a solid drive indicates its brand. A table with the approximate ratio of crushed stone is presented below.
Table 1. Selecting a grade of crushed stone for concrete
Brand of crushed stone Concrete grade M1200 M400-M500 M1000 M300 M800 M200 M600 M100 This table may have some deviations in one direction or another, but they are acceptable and can be adjusted by the ratio of cement and sand.
In practice, concrete M250 and less is made using gravel, and M300 and above is made using granite.
Concrete cannot be stronger than its fillers, that is, it is impossible to obtain M500 concrete from M400 cement. To obtain the right brand, it is necessary to select the correct proportions of all components.
To make a concrete mixture, you need to use several basic components. This list includes sand, cement, water and aggregate. Crushed stone is most often used as the latter. This building material comes in several varieties, each of which has its own characteristics.
Crushed stone is bulk material, which is obtained by crushing rocks, including boulders and gravel. In other words, crushed stone is usually understood as irregularly shaped stones that can belong to different rocks.
When dealing with the question of why crushed stone is added to concrete, it is necessary to emphasize several features. This building material is not always used when preparing a concrete mixture, but its inclusion in the composition allows you to solve a number of problems:
If you decide to use a filler, you should consider the following nuances:
Having figured out why crushed stone is in concrete, it is necessary to indicate several basic characteristics on which technical indicators ready mixtures:
Bulk filler is usually divided into several categories, taking into account the rocks from which this material was produced:
This type of crushed stone is obtained by crushing nonmetallic rocks, most often it is a monolithic rock. Granite quality building material regulates GOST 8267-93. This material is superior in strength to other types of filler.
Several categories can be distinguished depending on what fraction the crushed stone is:In construction work, the middle fraction (5-20 mm) is most often used. This option is considered optimal for laying highways, building foundations, constructing reinforced concrete structures.
Such bulk material is produced from rocks. Often, rock dispersion technology is used for mining after extraction from the quarry. Product quality must meet the requirements of GOST 8267-93.
The strength of these stones is lower than granite, but this variety has several advantages:
Gravel material has found application in the construction of pedestrian paths, filling reinforced concrete products, construction of sites.
Sedimentary rocks are used to produce crushed limestone. Stones in in this case are calcium carbonate. The advantage is the minimum cost.
There can be several grain sizes:Due to its low strength, limestone material has limited use. It is suitable for the construction of paths with light loads, work in the printing and glass industries, and the preparation of cement mortar.
Slag rubble is usually understood as stones different sizes, which are obtained from the slag used in production.
Depending on the size of crushed stone there are:You can use this filler for cooking. The most common application is thermal insulation.
Recycled crushed stone is called secondary because this material is obtained from construction waste, including old asphalt, bricks, and concrete. These products must meet the criteria of GOST 25137-82. The main advantage is low cost.
Disadvantages include low strength and frost resistance. Despite this, recycled materials are often used to strengthen weak soils and build roads.
To achieve maximum strength and durability of concrete, crushed stone must be selected carefully. Universal option does not exist, therefore, when selecting, it is necessary to take into account why the concrete is being prepared.
First of all, you need to check compliance with GOST. To do this, the seller is asked to provide accompanying documents for the shipment of goods. Another requirement is the minimum content of dust, sand and other impurities. The maximum figure is considered to be 2% of the total mass.
When choosing what kind of crushed stone is needed for concrete, you should be extremely careful in selecting the grain sizes. Large stones should be used in structures that must withstand vertical loads. Such crushed stone takes on the main load and acts as a frame.
Smaller fractions are chosen for reinforced products and those elements that must withstand high deflection loads.
Before you purchase all the ingredients to create the mixture, you need to select the appropriate crushed stone for concrete. Technical and performance characteristics finished products.
The table below shows the use cases recommended by the manufacturers.
It is necessary to add additional components to any concrete mixture, on which the final strength and everything will depend. important characteristics. To obtain high-quality composition It is necessary to use several elements - water, cement and high-quality filler. In most cases, crushed stone for concrete is used as a filler, which has good characteristics, suitable for construction. To obtain a high-quality composition, it is necessary to study all the main characteristics of crushed stone, as well as the varieties that can be used.
Experienced builders know that to prepare concrete, it is necessary to use cement, sand and water. To obtain different strengths, different proportions are used, but all components remain unchanged.
But in some cases, to create a special durable concrete, other components are added to the mixture, but the principle of creating the solution will not change. A building material such as crushed stone is used as a filler. As many people know, this stone uneven surface, and therefore the grip of the resulting composition will be much better.
Adding crushed stone to concrete has become popular for several main reasons, one of which is that the material is the cheapest compared to cement, but it has greater hardness and density. In addition, when crushed stone is added to a concrete solution, creep and the percentage of shrinkage of the mixture are reduced.
Concrete containing crushed stone will also crack less than regular cement mortar, but at the same time the water resistance will increase, as well as the density of the composition.
When crushed stone is added to concrete, you should be aware of certain nuances. Even despite the fact that crushed stone is a rather large filler and increases the density of the mixture, it must be added to the composition very carefully. The formation of “air pockets” is possible. This suggests that when making strong concrete, you cannot add only large crushed stone with increased hardness to the solution. It will be more effective to mix different fractions of different diameters with cement and sand. Thus, it is possible to produce a truly durable and reliable composition, while saving on cement, which is poured into the overall mixture.
Also, you should not add only fine crushed stone to the composition. To obtain quality concrete, not so much cement will be required, and therefore the effect will be much more noticeable if you use different sizes stones.
Concrete with crushed stone is very often used for the construction of hydraulic reinforced concrete structures, bridges, tunnels, stone supports and the construction various foundations. Gravel is also often used for decorative purposes during construction. landscape design. Coarse crushed stone is indispensable for construction purposes during the construction of roads.
If you want to add crushed stone to concrete, you must also take into account that the quality and strength of the mixture will be affected by the absence of dust and other impurities. That is why it is advisable to study GOST standards when purchasing crushed stone. The content of impurities should not exceed 2% of the total mass. The lower the indicator, the better the quality of the mixture. If there are any doubts after purchase, the crushed stone should be washed with water from a hose. This way it will be possible to remove a large number of impurities.
Main characteristics:
Depending on the method of extraction of the material, crushed stone is divided into several varieties.
Granite crushed stone is a non-metallic material extracted from hard rocks. In most cases, monolithic rock is used for mining. To obtain high-quality material, use GOST 8267-93.
Types of fractions in millimeters:
The most popular fraction in construction is considered to be the fraction with a diameter of 5-20 mm, which is quite often used for the construction of asphalt and the creation of concrete.
This type of crushed stone is used for the construction of reinforced concrete structures, in the construction of roads, as well as railway tracks, sidewalks and road platforms.
This type of material is produced by dispersion after extraction from quarries. Stones are also obtained by crushing rocks. During mining, GOST 8267-93 is used. In terms of strength, the material is not inferior to the previous variety. The advantages of the material include low background radiation, as well as low cost.
Building materials are divided into several types:
Fractions in millimeters:
The material is used to fill reinforced concrete structures, as well as in civil engineering, during the construction of platforms and pedestrian paths.
A similar variety is obtained by processing sedimentary rocks and limestone. Crushed stone is calcium carbonate and is sold at the lowest prices.
There are several fractions (in millimeters):
The limestone type is used for the glass and printing industries, in the production cement mortars, as well as during the construction of roads on which a small load is applied.
Crushed slag is friction waste used to produce certain types of chemicals. Depending on the size, crushed stone is divided into several sizes:
The material is obtained after processing construction waste, concrete, brick or asphalt. During production, we adhere to GOST 25137-82. This material is produced using the same technology as other types of crushed stone. The main advantage is low cost. In terms of strength and frost resistance, it is inferior to natural varieties of stones. Despite not the highest characteristics, crushed stone is used in road construction to strengthen weak soil. It is used as a filler for concrete mortar. Before purchasing, it is advisable to choose specific type building material that is suitable for a specific purpose, and also read the quality certificate that each seller must provide.
In order to purchase high-quality crushed stone for concrete, you need to familiarize yourself with the basic selection criteria. The quality of the resulting composition will depend on this.
It is important to choose the right gravel or crushed stone - what fraction, to be more precise. The crushed stone fraction is a collection of different particles of approximately the same size in poured concrete. Crushed stone will make up the majority of the entire solution, and, therefore, the quality of the resulting foundation will depend on its characteristics.
Crushed stone added to concrete will minimize the shrinkage process, and also increase the strength characteristics and make the foundation more resistant to loads. The strength of the mortar will depend on the strength of the concrete mixing. This indicator has a direct impact on the density of concrete. To reduce the number of voids formed in the solution, it is necessary to correctly select the fraction of crushed stone and sand. Most best option– use crushed stone of large and small fractions so that the voids between large elements are filled with small particles.
The connecting link in any concrete composition is cement. Portland cement, which contains 80% calcium silicates in its composition, is considered good for concrete. Increased content This substance ensures good adhesion of the resulting solution. Frost resistance indicators are also high, which is especially important in construction conditions in Russia. For construction, cement grade M500 is usually used. It must be stored in specially prepared premises.
Crushed stone is necessary to give strength to concrete. In most cases, fractions from 8 to 40 millimeters are used. It is important to ensure that various impurities and dirt do not fall into the composition. If you prepare the solution yourself, then use several types of crushed stone with different shapes.
To select the ideal ratio of all components, you should familiarize yourself with the manufacturer’s requirements for a specific brand of cement and brand of crushed stone. For example, to create a gazebo and flower bed, as well as small paths, you can use ordinary M100 cement. For the construction of a private house M250. For structures that will be subject to heavy loads - M400 or higher. There is no need to choose a brand with a reserve, since this way it will be useless to spend money on the necessary mixture.
There is also the option to use online calculator calculations and calculate all proportions.
After studying this information, you can understand what crushed stone is needed for concrete.
