Many people know that there is a sand cushion for the foundation, but not everyone can say for sure why it is needed and how it is created. As a result, beginners in the construction business often pour sand into the trench without any understanding and, as a result, only harm the entire structure.
The cushion under the sole of the foundation can perform three functions:
- Leveling. If the soil is not heaving and not mobile, then the only task of the sand is to level the bottom of the trench or pit for even placement of the solution or the correct distribution of the load from the FBS.
Compensatory. Heaving soils under the support of a house in winter can greatly affect the distribution of loads, leading in difficult cases to the destruction of a concrete tape or slab.
In this case, the task of sand is to compensate for deformations, to reduce them to an acceptable level for a given foundation.
Substitute If there is organo-mineral or organic soil under the house (for example, peat), then you have to put up with continuing decomposition processes.
In this case, the soil will necessarily be mobile, heaving and characterized by low bearing capacity. It has to be taken out to a great depth, until the end of the organic layer, and the trench is covered with sand.
How thick a pillow is needed under the foundation depends on what function it performs in this particular case.
Pillow device
The easiest way is to create a backfill that performs a leveling role. As a rule, its thickness in this case does not exceed 15-20 cm. It is enough to fill in the sand once, carefully level it, spill it with a small amount of water - moisten it and then compact it.
But such a minimum can be dispensed with either on non-rocky soils, or in the case of a deep foundation, below the level of freezing and relying on non-deformable soil layers. In other cases, you have to lay a compensating pillow. Its dimensions depend on the width of the base of the foundation. Exact data can be calculated from the table.
| 50-70 | 2.4*b | 1.2*b |
| 70-100 | 2*b | 1.15*b |
| 100-120 | 1.8*b | 1.1*b |
For example, if a foundation is laid with a base width of 60 cm, then the width of the pillow will be 60 * 2.4 = 144 cm, and the height will be 60 * 1.2 = 72 cm. A strip foundation with a tape width of more than 120 cm does not need a compensating pillow .
A compensating sand cushion is laid as follows:
Sand is considered a non-heaving material; also, due to its structure, it prevents the capillary rise of moisture from the underlying layers to concrete. But all this is typical only for sand that is not filled with water.
If a lot of moisture gets under the foundation, then it can radically change the properties of the pillow.
Therefore, in areas with a high level of groundwater or where there is a possibility of sedimentary water getting under the concrete, it is imperative to provide a system for removing moisture - drainage.
The process of laying a replacement cushion under the foundation does not fundamentally differ from a compensating one. The role of geotextiles and systems for water drainage is only increasing. In any case, the important point is the correct tamping. It is worth considering in more detail.
Watch our video compilation on the topic:
How to properly compact?
Clean sand practically does not shrink, but only after proper compaction. If this procedure is neglected and performed in bad faith, there is a high risk of subsidence with subsequent destruction of the foundation.
In order for everything to work out properly, you should adhere to the following rules:
It is more convenient and faster to carry out compaction work using a vibrating plate or a special building vibrator.
In some cases, you can use road construction equipment, and sometimes it’s good to tamp by hand.
Which method to choose depends on the characteristics of the site and the possibilities.
Sand selection
Few people think about what kind of sand to choose for a pillow under the foundation. They take the one they bring. However, the properties of this material affect the properties of the bedding to no lesser extent than the correctness of its laying.
For a foundation pillow, washed quarry or river material is best suited.
The ideal choice is gravelly. Do not forget that it is allowed to use other materials that meet the requirements presented.
However, it is difficult to correctly determine the loads and properties of a particular soil at home, so the easiest way is to take the material that is guaranteed to fulfill its task.
Watch our video compilation on creating a sand cushion:
Proffu » Recordings » Materials and tools » Sand filling under the foundation
Before starting construction work, many pre-calculate the required amount of material. This is the right approach to such a serious matter. But at this stage, a lot of questions arise. One of them: what kind of sand is needed for the foundation?
The choice of such material should be given special attention, since it is an important component, one of the main components used in the manufacture of concrete. The durability of the foundation - the future foundation of the house - will depend on the quality of the resulting mixture. The modern market offers a huge range of sand, both natural and artificial. How to make a choice so that the foundation does not suffer from it, the article will tell.
Even a person ignorant of construction issues will be able to guess that exceptionally clean sand is suitable for the foundation. Initially, various organic elements may be present in it: small twigs, grass, and so on. Such material is not suitable for construction work, therefore, there must be seeded sand, cleaned from foreign debris.
However, simple pouring is not enough when it comes to impurities such as lime or clay. Cleaning such sand is much more difficult, so when buying building materials, you need to immediately pay attention to this. The clay content in the sand is not more than five percent of the total mass, especially if a mortar is made for the foundation. Otherwise, the structure will shrink, crack after some time and will not be particularly reliable.
Sand cleanliness check
Before choosing which sand is needed for the foundation, you should check its purity. For this, a simple method is usually used. You will need any empty transparent bottle (glass or plastic). Sand is poured into it by one third and half filled with water. Then vigorously shake the bottle so that the components mix well with each other. After that, they put it in and wait for five to ten minutes. If the water in the bottle has become cloudy and dirty, then such sand is not suitable for the foundation. If a foreign substance appears on the surface, the layer of which exceeds half a centimeter, then such material cannot be taken either.
Now consider what types of sand exist.
Types of sand for embankment under the base
To ensure the reliability of the structure under construction, according to the norms of SNiP, it is necessary to use loose mixtures. The market sells sedimentary rocks in three types, depending on the place of their extraction. This is sand:
- career;
- river;
- nautical.
To answer the question of which one is most suitable for a foundation pillow, you should familiarize yourself with the characteristics and nuances of using each type.
Quarry sand
This raw material is mined in quarries by breaking rocks. An important indicator of the reliability and strength of quarry sand is its moisture content. A ratio of one to five percent is considered acceptable. Suitable humidity can be determined visually. It will not be possible to make a dense lump out of the sand - it will simply crumble.
Quarry building sand is considered the cheapest material. The price for it ranges from three hundred to seven hundred rubles per cubic meter. This is due to its low quality due to the large amount of impurities of clay and other substances. Nevertheless, this raw material is in considerable demand.
Types of quarry sand
Depending on the type of processing, quartz raw materials are classified as follows.
1. Sandy soil. It is a crude mixture with various impurities. As a rule, summer cottages are leveled with it and trenches fall asleep.
2. Washed sand. It is extracted from flooded deposits using hydromechanical equipment. The technology allows you to collect the mixture without any impurities and unnecessary components. This material is used in the production of roads, paving slabs, concrete, bricks and reinforced concrete products.
3. Seeded sand. It is cleaned technically and mechanically from large particles and stones. Typically, such raw materials are used to prepare a mass of plaster, masonry mortars and in casting stone products.
river sand
This raw material is mined from the very bottom of freshwater rivers. It rarely contains organic compounds and impurities. Therefore, river sand is considered a clean and natural product, which is designed for multi-purpose use. It is an ideal material for laying foundations, creating drainages and diluting mortars necessary for interior decoration of a house. Due to natural polishing, river sand has a perfectly smooth shape and a fine fraction within two millimeters.
Thanks to all these advantages, this material becomes a versatile and desirable, but rather expensive raw material for the foundation. Thus, the price of building sand extracted from the river can vary from seven hundred to one thousand rubles per cubic meter.
River sand classification
Raw materials from the bottom of the river can be very different from each other. Therefore, you should deal with a variety of grains of sand. They can be of several fractions: from 0.7 to 5 millimeters. A filling of fine grains of sand shrinks and compacts strongly, so it is only suitable for lightweight buildings. The following types of bulk river material are also distinguished.
1. Coarse sand. These are pebbles about five millimeters in size. They are obtained by splitting rocks with the help of special crushing and grinding equipment.
2. Coarse sand. It has an unobtrusive neutral color, it is mined in dry rivers. Ideal for finishing and decorating the room.
3. Washed river sand. These are medium sized grains. They are gray or yellow in color because they contain oxides of iron and silicon.
Positive aspects of river sand
River sediments have several positive qualities that are of great importance for foundation construction. They meet technical and aesthetic requirements, do not rot and are not exposed to aggressive environments. River sand is characterized by high moisture resistance and excellent sound insulation. It is also a safe and environmentally friendly material.
For the construction of multi-storey buildings, only a large-fraction type is used, and for capital houses, an average crumb is already suitable. River sand is also ideal for landscaping, playgrounds, landscaping and decorating rooms.
Sea sand
Sea crumb is also exactly the material that is needed for the foundation. Sand is initially no better than river sand, and sometimes worse. This is due to the presence of organic impurities (algae, shells) and foreign objects. But sea sand must be cleaned of foreign matter and washed, so it is considered clean and of high quality. Due to this, this material is the most expensive, and not everyone is willing to pay for it. It is more appropriate to use sea crumbs for construction where it is sold nearby and is cheaper.
Sand fractions
Any sand can be classified according to its size. Experts distinguish the following types of fractions.
- Very thin. These are grains of sand about 0.7 mm in size. They are suitable for arranging playgrounds and are unsuitable for construction.
- Thin. Grains in size reach from 0.7 to 1.0 millimeters. This is a non-dense material. You can not use such sand for construction, but it will be fine for making lean concrete.
- Small faction. It is a grain size of 1.5-2.0 mm. When using it, the consumption of the cement mixture increases.
- Average. Grains (2.0-2.5 mm) can be used to create standard concrete.
- Large. Sand particles in size reach three millimeters. This fraction is ideal for diluting high-quality concrete mix, which will be used in large-scale construction.
- Very large. Particles larger than 3 mm in diameter. They are added to the foundation cushion and used to distribute the mass of the structure.
The choice of sand for the foundation
So what kind of sand is needed, river or quarry? Experts agree that the first option is most suitable for the construction of foundations. It will create a layer that will increase the strength, stability of the building, prevent "walking" and the formation of cracks.
However, river sand will not be affordable for everyone. In this case, it is allowed to use career crumbs, but always washed. A sand-gravel mixture is also suitable, which improves the quality of the composition for laying under the pillow.
Required amount of sand
Usually, one part of cement is taken for five parts of sand. But this calculation is suitable if the solution is made only from these two components. The ratio of sand, gravel and cement for the foundation will be completely different. As a rule, they are taken in the following proportions: four parts of sand, two parts of crushed stone and one part of cement.
As can be seen from the calculations, it is always necessary to take more sand than other components. The amount of materials itself directly depends on the height of the pillow and the building itself. It is better to buy sand with a small margin so that you do not have to buy it at the wrong time. The remains can be adapted for the preparation of solutions for wall decoration or masonry.
Summarizing
When answering the question of what kind of sand is needed for the foundation, it should be noted that river grains of the middle fraction are considered ideal. Such material has excellent properties for construction purposes. It allows you to build the most solid foundation that will last a long time and will be an excellent foundation for construction.
It is necessary to purchase sand from reliable manufacturers so as not to stumble upon low-quality raw materials. It is recommended to check the material before purchase for the level of moisture and the amount of foreign matter. It is also worth paying attention to the appropriate size of the purchase. As a rule, there should be about one and a half tons of sand in a cubic meter.
When laying the foundation, it is important to correctly and correctly choose building materials. Especially carefully it is necessary to choose sand, since it is precisely the strength of the solution for the foundation depends on it, and hence the strength of the entire foundation. To the question of which sand is better to choose for the foundation, we will answer in this article.
Sand selection
Foundation sand is a loose material obtained from sedimentary rocks or artificial creation. The quality of sand does not depend on its method of obtaining, it is important to consider only its purity.
If you can find foreign objects larger than half a centimeter in it, it is not suitable for laying the foundation. Foreign objects may include branches, leaves, organic debris.
Of course, you can try to clean the sand yourself by taking a sieve and sifting it, but just imagine how much time and effort it will take you to do this process. By sifting the sand, you will only remove large impurities, but what about the content of such elements that are undesirable in the sand for building the foundation of a house, such as lime or clay.
It is better immediately choose high-quality sand and get to work. Remember that high-quality sand suitable for making mortar should not contain more than 5% impurities. In addition, a large number of additives will degrade the strength of the sand, which will affect the foundation and the house or building itself. Content gravel in sand should not exceed 10%, since gravel is an integral element of the mortar for pouring the foundation.
Of course, you can only find ideal sand by conducting a special examination of its compliance with all standards in the laboratory, you will find out the percentage composition of impurities in the total mass and other indicators. But such an examination is a costly and lengthy process, therefore you can determine the quality of sand by improvised methods.
Pour sand into a transparent bottle by a third, and then fill up to half with clean water and shake. Then let the mixture stand for 5 minutes and look at the transparency of the water. If it has become cloudy and dirty, then the sand contains a lot of impurities. Floating foreign matter is also a bad sign, and such sand is unsuitable for construction. If the water is clear and without impurities, then the sand is ideal for laying the foundation.
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Origin of sand
Which sand is better - quarry or river sand, we'll talk in this part.
Quarry sand
Quarry sand is mined in a quarry, destroying rocks. It is of lower quality than river, but there are exceptions. When choosing quarry sand an important factor in its reliability and strength is the moisture parameter. Its percentage should be from 1 to 5%. Humidity of 5% is determined by eye by the fact that it is impossible to make a dense ball or snowball out of sand - it crumbles.
To correctly determine the moisture parameter, you can resort to the following method. To determine the moisture content of quarry sand, take a container and weigh it. Then, weigh 1 kg of sand in it and hold it at a low heating temperature for about half an hour, and then weigh only the sand. Humidity will be calculated using the formula: the mass of sand after heating minus the mass of the container divided by 100.
Quarry sand is cheaper than river sand, since its extraction method is less expensive.
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river sand
River sand is ideal for laying foundations, and is also used in diluting mortars for interior decoration of a house or creating drainages. Therefore, such sand versatile and multifunctional. Its fine fraction of one and a half to two millimeters and the absence of impurities make it desirable, but expensive building material.
In addition to river sand, they also emit nautical, but in modern construction it is used where it can be quickly brought from, otherwise it the price exceeds even the river. In terms of quality, it is no better than river water, and sometimes even worse due to organic impurities (shells, algae) and foreign objects.
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Sand fractions
Depending on the size of the grains of sand, the following types of fractions are distinguished in the composition of sand:
- Very thin contains grains of sand up to 0.7 mm, but due to the low fraction it is unsuitable for the foundation. The foundation based on it will turn out to be as fragile as possible.
- Thin contains grains of sand from 0.7 to 1 mm. Such sand is loose, therefore it is also not suitable for foundation mortar. Usually fine sand is used to pour concrete.
- Very small contains grains of sand up to one and a half mm, but still not suitable for pouring a foundation again, as the strength will still not be optimal.
- Small contains grains of sand from one and a half to 2 mm. And again, it is not suitable for pouring the foundation due to the high cost of cement for it.
- Average contains grains of sand from 2 to 2.5 mm and is ideal for pouring foundations due to its strength and high performance properties.
- Large contains grains of sand up to 3 mm and is intended for the manufacture of concrete of high quality and expensive grades. This sand is very expensive.
- Sand increased size contains grains of sand up to 3.5 mm and is used for the manufacture of sand cushions, designed to increase the strength of the base and distribute the load evenly at all corners.
The pouring of the foundation assumes that the edges of the medium sand you have chosen should be sharp. It is the sharp edges of the grains of sand that increase the operational properties of the solution and make it as durable as possible.
What kind of sand is needed for concrete, plaster or bricklaying. See which is better, river or career.
This type of sand is cleaned naturally, all impurities are washed out of it. Sometimes it is also found under the name "washed". The particle size of river sand, as a rule, is from 0.3 to 0.5 mm.
Attention! !
Quarry sand
Particles of quarry sand are much smaller than those of river sand. Fraction from 0.6 to 3.2 mm. Quite often, clay or even grass and tree roots are present in the sand from the quarry (usually when the quarry is expanded)
Which sand is best
It all depends on the goal.
For masonry. It is better to use quarry sand, it does not “settle” so quickly in the solution. The solution is more plastic, due to the presence of clay.
For screed. River is almost always used, it often contains very small pebbles, which provide additional volumetric reinforcement.
For concrete. Concrete structures always require high strength. Clay increases ductility, but at the same time greatly reduces strength, respectively, it is better not to use quarry sand. To prepare concrete, it is better to buy river sand, of course, you will need to add crushed stone.
For plaster. Career in this case is more suitable, clay inclusions are not so critical, since increased strength is not required, and a fine fraction allows you to get a smoother surface.
Concrete is made up of sand, cement, gravel and water. Each of these components has its own role both in the manufacture of a concrete structure and in its subsequent operation.
Sand for concrete is a fine aggregate that covers the voids that form between the rubble. It allows you to evenly distribute internal stresses during concrete hardening and reduce the final cost of the mortar by reducing the amount of cement to be kneaded.
The main thing is to take into account all the requirements for preparing the solution, choose those components that are best suited, and observe the appropriate proportions.
Particle size
Bulk material is divided into two classes depending on the particle size: I and II class. As part of a higher quality class I, there are no very small, thin and very thin groups, which are undesirable components for mortars. If they are present, the relationship between larger fractions worsens. Therefore, when preparing the solution, it is better to use class I sand.
Fraction classification
According to GOST 8736-93, in terms of fineness modulus, division can be:
- very large;
- increased size;
- large;
- average;
- small;
- very small;
- thin;
- very thin.
In reality, the division is usually conditional. May be:
- small;
- average;
- large.
To prepare a high-quality durable solution, it is better to use a large fraction. Preferably with a particle size of 2-2.5 mm. With a smaller size, the cost of the prepared solution will increase significantly, and the quality will decrease.
Mining place
The place of extraction has a significant impact on the composition and properties of the material. It is customary to distinguish river, quarry, sea and quartz. Sand is mined in an open pit.
Career
In the quarry there are impurities of clay and stones, so it can be used exclusively as a backfill for foundations or concrete screeds. In the preparation of concrete, quarry sand can only be used after washing with water, carried out at the place of extraction. When performing such an operation, clay and dust particles are removed.
River
River sand initially no longer contains clay. It may contain a minimum of stones. It is actively used in construction work, allowing you to get a better solution. It is distinguished by the ability of natural precipitation, therefore, when preparing the solution, it must be constantly mixed.
It should be borne in mind that the cost of river material is slightly higher than quarry material. When choosing, you should analyze what is better: reducing the cost of manufacturing a concrete structure or ensuring sufficient strength.
Marine and quartz
Marine in its characteristics is close to the river. Differs in purity and uniformity of granulometric structure. May require additional cleaning due to possible shell content.
Quartz is the result of mechanical crushing of rocks containing quartz. Homogeneous, pure and chemically inert. Obtained artificially.
Processing method
Depending on the processing method, there may be:
- alluvial, obtained by washing;
- seeded, obtained by sifting the feedstock to remove large particles and debris.
Characteristics
The requirements for sand used in the preparation of concrete are reflected in the relevant regulatory documents. Some characteristics can be checked exclusively in the laboratory, others can be checked directly on the construction site.
Volume weight
An indicator that reflects the mass of 1 m³, which is in its natural state. A cube of wet sand with all impurities weighs on average about 1500 - 1800 kg. The smaller value is preferred.
Compound
The composition may be:
- granulometric, which reflects the ratio (in percent) of grains of different sizes;
- mineral: quartz, dolomite, feldspar and limestone;
- chemical, depending on the elements present in the composition, a possible area of \u200b\u200buse is determined.
Example of particle size distribution:
Example of a chemical composition:
| Sl02 | Al2O3 | Fe203 | Ti02 | CaO | MgO | SO3 | K2O | Na2O | P.P.P. 1000C |
Sum | Content CO2 |
CaCO3 |
| 78,26 | 6,48 | 1,45 | 0,12 | 5,89 | 0,70 | 0,12 | 0,96 | 0,64 | 5,35 | 99,97 | 4,92 | 11,2 |
Mineral composition example:
Humidity
As a rule, this characteristic is equal to 5%. If the mixture is dried, the indicator will decrease to 1%. When moistened by precipitation, the value can increase up to 10%. The amount of water added to the solution at this humidity should be reduced.
Moisture requirements are important, since the amount of water added to the solution depends on it. Humidity is determined by calcining a kilogram of the mixture. The indicator will be equal to the difference in the weight of wet and dried.
At the construction site, the humidity level can be checked as follows. If the sand is compressed into a lump, it will have to crumble. If this does not happen, the humidity is more than 5%. Although this indicator is still better to control in the laboratory.
| Sand volume, cm3 (ml) | Moisture content of sand, %, at the density of sand particles, g/cm3 | ||
| 2,6 | 2,65 | 2,7 | |
| 448 | 2 | 2,9 | 4,1 |
| 450 | 2,6 | 3,5 | 4,7 |
| 452 | 3,3 | 4,2 | 5,3 |
| 454 | 4 | 4,8 | 6 |
| 456 | 4,6 | 5,5 | 6,6 |
| 458 | 5,3 | 6,1 | 7,3 |
| 460 | 5,9 | 6,7 | 8 |
| 462 | 6,5 | 7,4 | 8,6 |
| 464 | 7,2 | 8 | 9,3 |
| 466 | 7,8 | 8,7 | 9,9 |
Porosity coefficient and bulk density
The porosity coefficient reflects the ability of sand and, accordingly, the ability of concrete to pass moisture in the future. Can only be determined in the laboratory.
The average value of bulk density is considered to be 1.3 - 1.9 t / m3. 1.5 t / m3 is considered optimal. A lower value may indicate the presence of undesirable impurities, a higher value may indicate excessive moisture. The necessary information must be written in the accompanying documents.
Which one to give preference?
To understand what kind of sand is needed for concrete of a particular brand, it is necessary to take into account the upcoming type of work.
masonry
Brick and large-block masonry is best done using river. If it is necessary to increase the plasticity of the prepared solution, a small amount of unwashed quarry can be added to the river one, which will also help reduce costs.
Concrete
For the preparation of concrete, it is preferable to use medium or coarse river sand, to which a little washed quarry sand can be added. It should be noted that grains of quarry sand, in contrast to river and sea sand, have an irregular shape and a rough surface. Under the influence of an aqueous medium, the surface of the particles is polished, which significantly impairs adhesion to the remaining components of the solution.
However, it is not always possible to completely remove clay by washing a quarry. Therefore, when preparing a concrete mixture, it is preferable to use river sand. He's already washed. The particles are approximately the same size. It does not contain clay, which significantly reduces the strength characteristics of the prepared solution.
Criterias of choice
Thus, when choosing sand, you need to focus on:
- cost - river and sea will cost more than a quarry.
We prepare concrete, maintaining proportions
To obtain high-quality concrete, it is necessary to properly maintain the ratio of sand and cement. The optimal ratio of components (c - cement (M400, M500); u - crushed stone: p - sand) of the solution is as follows:
| Concrete brand | Mass ratio: c:shch:p (kg) |
| 100 | 1:7:4,6 (1:8,1:5,8) |
| 150 | 1:5,7:3,5 (1:6,6:4,5) |
| 200 | 1:4,8:2,8 (1:5,6:3,5) |
| 250 | 1:3,9:2,1 (1:4,5:2,6) |
| 300 | 1:3,7:1,9 (1:4,3:2,4) |
| 400 | 1:2,7:1,2 (1:3,2:1,6) |
| 450 | 1:2,5:1,1 (1:2,9:1,4) |
The brand of concrete is important. If it is below M300, it is better to take sand with a particle size of less than 2.5 mm. Such concrete is traditionally used for pouring the foundation for a garage, one-story buildings, and outbuildings. For grades above M350, used in the construction of multi-storey buildings, floor slabs, armored belts, it is worth taking a river grade with a grain size of 3 mm or more.
In the most general case, when preparing a solution, you can use the following data:
| Concrete brand | River sand particle size, mm | Volumetric composition per 10 l: sand: crushed stone (l) | Mass ratio: cement: crushed stone: sand (kg) |
| 100 | up to 2.5 | 41:61 (53:71) | 1:7:4,6 (1:8,1:5,8) |
| 150 | 32:50 (40:58) | 1:5,7:3,5 (1:6,6:4,5) | |
| 200 | 25:42 (32:49) | 1:4,8:2,8 (1:5,6:3,5) | |
| 250 | 19:34 (24:39) | 1:3,9:2,1 (1:4,5:2,6) | |
| 300 | 17:32 (22:37) | 1:3,7:1,9 (1:4,3:2,4) | |
| 400 | from 3.5 | 11:24 (14:28) | 1:2,7:1,2 (1:3,2:1,6) |
| 450 | 10:22 (12:25) | 1:2,5:1,1 (1:2,9:1,4) |
And water, mixed in certain proportions, creates such a super-strong building material as concrete. Each ingredient plays its own important role. So, sands are an integral part of the concrete mix, which fills the space between the rubble. The quality of the fine aggregate plays a key role, since the wear resistance and strength of the final product depends on the correct distribution of internal stress.
General requirements for selection
Sand for concrete, which is used for the manufacture of concrete mortar, must comply with GOST standards. The material is suitable if it contains less than ten percent of particles with a fraction of up to 0.14 mm and no more than three percent of impurities represented by dust, silt and clay. It is the presence of the latter in the mixture that can adversely affect the frost resistance and strength of concrete, since it covers the grains of sand, preventing them from properly connecting with the rest of the components. Also, according to the standards, the content of large-sized particles of more than 10 mm is not allowed, and the proportion of particles with a size of 5-10 mm should be within five percent of the total mass of the bulk component. Organic inclusions in the material, represented by humus or plant elements, should be absent.
Particle size
River - the most optimal variant of the filler of concrete mixtures. To figure out what kind of sand is needed for concrete, they are first determined with the most important parameter when choosing a bulk building material - the fineness modulus (fraction). Distinguish:
- very large (more than 3.5 mm in size);
- increased fraction (within 3-3.5 mm);
- large (2.5-3 mm);
- medium size (2-2.5 mm);
- small (1.5-2 mm);
- very small (1-1.5 mm);
- thin (0.7-1 mm);
- very thin (up to 0.7 mm).
To determine the particle size modulus, manufacturers sift sand alternately through sieves with fractions of 10 mm, 5 mm, 2.5 mm, 1.25 mm, 0.63 mm, 0.315 mm and 0.14 mm.
A simplified classification can be represented as follows:
- small;
- average;
- large.
The production of concrete involves the use of coarse sands with a sufficient amount of finer grains, otherwise the concrete mixture will contain many voids. The resulting voids will be filled with cement, which means an increase in the cost of the final product. It has been noticed that the grains of the same fraction are in poor contact with each other, forming more free space. Therefore, a mixture of different particle sizes is massively used to obtain the highest density between the elements.
Based on particle size, bulk materials are classified into two classes. The first class is distinguished by the absence of microparticles less than 1.5 millimeters in diameter. Such a sandy material is considered better, since the presence of very fine aggregate negatively affects the settling density of larger fractions. The second class, respectively, includes small components. That is why, for the preparation of high-quality concrete, loose first-class concrete is used.
Kinds
Sand is a fine-grained sedimentary rock that occurs in finished form or obtained by crushing rocks. In addition to grain size, an important indicator is the place of extraction, which determines its properties. Allocate:
- river;
- nautical;
- career;
- quartz.
River sand is preferred because it lacks clay and contains very little stone. It is somewhat more expensive than other types of bulk, but the best in quality. Its grains of sand are uniform and have a smooth oval shape, the density of their settling is much higher than that of a quarry, the shape of which is not symmetrical and has irregularities on the surface. It is extracted with the help of dredging devices that suck in water along with sand and transfer the mixture to storage. In this case, the water has an outflow back into the pond.
The properties of sea sand are similar to river sand. Its peculiarity is the content of small grains of shells and sea stone. Therefore, it needs additional cleaning. Sea salt makes grains of uniform size and regular shape. It is the most expensive bulk material because it is mined on the seabed using costly technologies.
The composition of quarry bulk is often burdened with clay impurities and stones, so after mining it needs to be washed from foreign particles. He is the cheapest. The extraction of rock in sand pits is the most massive.
Quartz sand material is mined by artificial crushing of quartz rocks with special grinding plants. It is obtained without various kinds of impurities and is characterized by chemical neutrality. Based on the processing options, there are the following ways to clean the material:
- alluvial (method of purification by water washing);
- sifted (according to this method, sieves are used for screening).
Sand washing takes place right at the place of extraction. To do this, the material is immersed in water and mixed several times. Thus, various kinds of impurities and dust depart from the grains of sand. Unnecessary particles float up and are separated from the total mass. This procedure is carried out several times. True, the cost of bulk increases significantly. Sifting is a less expensive procedure, but it does not get rid of micro-dust particles.
Material characteristic
Sand can perfectly absorb and retain moisture. Different kinds of sand can have different physical and chemical characteristics depending on the composition, which can be:
- chemical;
- mineral;
- granulometric (display of the composition of particles in percent depending on the fraction).
An important indicator is the actual weight of one meter of cubic sand. It fluctuates between 1.5-1.8 tons. Less weight is considered better because the mass of impurities is minimal.
Humidity plays an important role. Normally, it should be 5%. The amount of water added to the concrete solution depends on this indicator. During home construction, you can check the moisture content of the material “by eye”: if, after squeezing in a fist, the sand does not crumble, it means that the normal level of humidity has been exceeded, and the mixture will need less water.
In modern construction, sand is used very actively and almost everywhere. At the same time, there are about 10 different varieties of this material, but in the practice of Russian builders, two types are most common: quarry and river. Naturally, each type has those properties that determine its advantages and disadvantages as a building or finishing material. Therefore, non-professionals who decide to build some kind of structure on their own often face a choice:
Quarry sand - advantages and disadvantages
Quarry is called sand, mined in quarries, from huge layers located at a certain depth underground. The quality of such sand is largely determined by its origin. The fact is that such underground sand is formed as a result of weathering of rocks. This process has been going on for centuries, decay products are deposited underground, eventually turning into caked masses of sand.
The formation of sand deposits results from the weathering of rocks such as mica, quartz, feldspar and partly limestone. The composition and characteristics of the sand depend on which rocks prevail in a particular area.
What must be taken into account when deciding which sand is better than quarry or river sand is the possible presence of impurities in the total mass of natural material. Clay contamination for quarry sands is a common phenomenon and only the concentration of foreign matter differs depending on the deposit.
Another important characteristic is the heterogeneity of fractions. In the mass of quarry sand, there are both very small and very large particles, often fragments come across in it, which, in terms of size, can be attributed to fine gravel. However, in the case of using sand for construction purposes, this property cannot be called a minus. The fact is that the heterogeneity of sand fractions and the presence of various impurities in it causes higher binding characteristics of sand.
So let's sum it up. Quarry sand is characterized by increased surface roughness of the particles, as well as the angularity of their shape.. This makes it excellent for use as an additional bonding agent for binders in mortars. There are also construction areas in which it is recommended to use quarry sand. It makes an excellent pillow for a deepened strip foundation. From this point of view, no other variety can be compared with quarry sand.
River sand - pros and cons
Now let's look at the main characteristics and properties of river sand in order to try to answer the question of which sand is better than quarry or river sand by comparison. River sand, as its name suggests, is mined from riverbeds. This circumstance is due to extremely low content of various impurities in it especially clay rocks and loams. They are simply washed away by the current, which provides natural cleaning of the sand.
Also, the constant exposure to water to which river sand is exposed leads to the fact that it the particles are approximately the same size and almost perfectly rounded shape. Due to this, this material is actively used in landscape design to create the desired decorative effect.
One of the advantages of the material is the fact that for the arrangement of children's sandboxes or volleyball courts, it is imperative to use river sand.
If we talk about construction, then the main properties of river sand, in addition to shape and size, should be recognized as a low ability to absorb and retain moisture, as well as environmental cleanliness and safety.
Given all this, river sand is used mainly for decorative finishing materials. For example, if it is planned to arrange a cement screed on the floor in the house, then river sand is better suited for these purposes. It will not accumulate moisture in itself, and will also help to obtain a more even and smooth surface of the coating.
For the same reasons, river sand is the preferred material for making paving slabs. In Krasnoyarsk, it is also used in the construction of drainage and filtering systems.
In fact, the only, but very significant minus of river sand as a building material is high price. The process of its extraction is associated with the use of complex expensive equipment; special barges and powerful hydraulic pumps are required to lift rock layers from the bottom of the channel and subsequently flush it. As a result, the cost of the final product is very high.
It is precisely because of the significant cost that when deciding which sand is better than quarry or river sand, builders often prefer the first. The issue of price becomes especially relevant when carrying out rough construction work, for example, arranging the foundation, creating open areas for cars, etc. And here for finishing work, especially internal, it is recommended not to save and choose river sand, the use of which provides a better result.
Our company is engaged in retail and wholesale deliveries of river and quarry sand in Krasnoyarsk. For more information and ordering delivery, call the phone number listed on the "" page.
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