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Density of alluvial sand kg m3. Bulk density of bulk materials. Factors Influencing the Specific Gravity of Sand

Average density of sand - important indicator, on which the operational properties of the substance and the future parameters of the concrete building mixture, the strength and stability of buildings, as well as the possible consumption of raw materials directly depend. It shows how much sand is contained in one unit of volume, which is taken as a cubic meter (1 m3).

The amount of a substance that fits in 1 m3 strongly depends on the type of sand - for example, fine building sand is more dense than medium-sized sand, since in the first case the gaps between the individual particles of the building material are much smaller, and a large mass fits into one cubic meter.

This parameter is closely related to such material indicators as voidness and moisture, the degree of compaction and porosity. The features and correctness of the measurement of parameters can also introduce a certain error into the final result. Between these factors there is the following relationship: the greater the void between the particles and the moisture content of the substance, the smaller the bulk characteristic and the less pure sand fits in a cubic meter. This rule identical for humidity, but with the opposite sign - due to the adhesion of fractions, the wet building material is compacted.

Also, the density depends on the structure of the grains, with a decrease in the size of which this characteristic grows, and also on the content of clay and other impurities. For the above reasons, the density of river sand is usually higher (average coefficient 1.5) than that of purified sand (for construction, the ratio is 1.4).

What varieties are found?

Density in kg / m3 is an ambiguous characteristic that has two main varieties that differ in definition, some features and methods of measurement:

True. It is the ratio of body weight (in this case dry sand) to its volume and is measured in kg/m3. This does not take into account free voids between individual particles, that is, we are talking about the density of the material in a compressed state. True density (like any other substance) is a constant value.
Bulk density. An indicator that takes into account not only the volume of the substance itself, as in the previous case, but also all the existing gaps between the particles. Bulk is always less than the true and average density, measured in kg / m3.

There is also an average value, which has already been mentioned above.

How to choose sand for sandblaster, can be found here.

Parameters various kinds material

As mentioned earlier, the density varies greatly depending on the properties of the raw material. The following table is intended to help track this fact:

Thus, one cubic meter of dry sand will have a mass of 1200 to 1700 kilograms, and a cube of wet sand will have a mass of 1920.

The table does not reflect all types - a more extended list with the coefficients necessary to calculate the density of raw materials can be found in reference sources.

In order to measure the density, the following methods are used on site:

Apply conversion factors that differ for each type of material. This method is not entirely accurate, since the measurement error can reach 5%. With large quantities of raw materials, the losses amount to more than one cubic meter!
Weighing bulk raw materials (for example, river) together with a vessel completely filled with it, after which the calculation is made by dividing the mass of sand by the volume of the vessel.

The determination of bulk density plays an important role in construction, since the number of cubes of raw materials required for the work largely depends on its value. This is especially important in cases where every cubic meter counts.

Sand is a loose natural material obtained as a result of the natural destruction of rocks under the influence of external factors. It may contain a small amount of various impurities. It is used in almost all types of construction. To properly mix the solution, you need to know the density of the sand, since the proportions of the remaining components depend on it. It also affects the volume of purchases, for example, for arranging a pillow under the foundation.

What is density and what does it depend on?

Density shows how many grains of sand in kilograms are placed in 1 m3. It is measured in kg / m3, sometimes in t / m3 or g / cm3 (this indicator affects). But this value is not always constant, as it can change depending on the following conditions:

1. Grain size. It happens fine-, medium- and coarse-grained. The larger the grain of sand, the lower the density, and, conversely, the finer ones fit more densely. Coarse and medium-sized sands are used for the manufacture of building materials and masonry mortars, and fine-grained sands are used for the production of dry building mixtures.

2. Porosity. Shows the number of voids. The high porosity option has a lower density. If it is loose, then the value is 47%, if compacted - 37%. The degree of porosity decreases when the sand grains are saturated with moisture, as they are enveloped in water and the voids between them disappear. It also decreases after transportation, as during movement everything is compacted due to vibration. Different fractions have different degrees of porosity. For building sand from large and medium grains, it is 0.55, for fine sand - 0.75. The denser it is laid, the greater the load from the foundation is able to withstand and distribute it more evenly.

3. Moisture coefficient. Before buying, be sure to check the degree. The more water it contains, the lower the density. The weight of 1 m3 of raw sand differs significantly from the same amount of dry sand.

4. Impurities. Depending on their volume, the density of sand kg/m3 also changes. It may contain clay, dust, salt, gypsum and more. The density of pure material is about 1300 kg/m3, with clay impurities - 1800 kg/m3. To remove contaminants, it is washed, but because of this, the cost increases markedly.

Types and prices

There are several types of densities:

true;
bulk (medium).

The first type is otherwise called specific gravity, it is also measured in kg / m3. The true density shows how much is in one cubic meter of bulk building material, without taking into account the voids between the grains. Calculate it in laboratories empirically. Its value for non-metallic sandy rock is 2500 kg/m3.

Bulk density shows the amount in one cubic meter, taking into account voids and gaps. Its value is always less than the true value. To measure it, you need a bucket of 10 liters. Sand in the usual uncompacted state is poured from a height of 10 cm from the edge of the container, until a slide appears above it. As soon as the bucket is full, the excess is leveled with a metal ruler, without compacting the sand, after which the container is placed on the scales. The result obtained must be divided by the number 0.01, which means the volume of the bucket, converted to cubic meters. For example, sand weighs 16.5 kg, it is equal to: 16.5 / 0.01 = 1650 kg / m3. In this case, it is convenient to use the formula P=M/V, where P is the density, M is the mass, V is the volume. And, conversely, knowing the compaction index, it is calculated how much the bulk building material weighs, for this it is multiplied by the volume of the container - M \u003d P * V.

The true density of building sand is a constant value. For calculations, the average value is used. Prices vary depending on its type, purity and size of fractions. Uncleaned is much cheaper than washed. Therefore, if a small batch is required, then unwashed sand can be purchased and cleaned of impurities on its own, especially if it is necessary for the construction of an unloaded structure. If you need to make a foundation, then you should purchase only clean and high-quality material. Clay and other impurities reduce the degree of adhesion of grains of sand to cement, which reduces the strength grade of concrete.

Table with prices at which you can buy building sand:

When choosing sand, one should take into account: the lower its density, the more binder powder is required to fill the voids between the grains of sand and connect all the components, as a result, the cost of the mortar increases.

The degree of radioactivity of most bulk building materials is the first, but it is better to check the quality certificates, especially if it will be used to build a house, in this case only the first class should be.

For construction needs, natural sands of various origins are used - river, sea, quarry, dune, etc. Their differences are in the method of extraction, the percentage of clay and organic impurities, as well as dust particles, which adversely affect the quality of concrete mixtures and the strength of finished building structures. A certain role in the scope of this or that type of sand is exerted by the degree of its contamination, the shape of the grains, the cost of the material and its availability, fractional composition and humidity.

Differences and features of quarry sand

The difference between the most common types of sand - quarry and river - is the way they are mined. Both of them belong to natural inorganic materials and are extracted as a result of mining, but in the first case, sand is extracted by an open method, and in the second - by hydromechanical from the bottom of the rivers. In its turn, quarry sand subdivided into:

seeded;
alluvial, or washed;
unfinished, low quality.

In the first case, it is distributed into fractions by sieving, while removing large inclusions. Such sand is not clean enough, since clay, lime and soil impurities can be traced in its composition. In this regard, the use of the material is allowed with low technical requirements for the work performed.

Alluvial sand is subjected to hydromechanical treatment with water, which eliminates unnecessary components, which ultimately affects the purity and quality of the bulk material.

Developed quarries can be located on plains, slopes, mountains or beds of dried rivers and reservoirs. Depending on the composition of sand grains, quarry sand can be:

quartz;
limestone;
feldspar;
dolomite, etc.

Plain quarries are flat areas with thick sandy layers lying just below the ground level. The presence of groundwater and the depth of development directly affect the moisture content of sand, which can be both dry and flooded. Sloping areas are located on hills, due to which the rock always remains dry, and water quarries, although they do not have surface water, are still distinguished by the presence of flooded sands. Their extraction, in this case, is carried out using hydromechanization in the form of dredgers and rippers. Mining quarries provide the construction industry with quartz sands.

According to the size of sand grains, the material is divided into seven groups, starting from very thin (fine size modulus up to 0.7) and ending with increased size (fineness modulus 3-3.5). Table 4 of GOST 8736-2014 indicates the maximum percentage by weight of clay and dust-like particles in building sand ranging from 2 to 10%, depending on the group of bulk material, as well as the presence of lumpy clay - no more than 0.25-1%.

Material characteristics

Untreated quarry sand is much dirtier than river sand, but 1.5-2 times cheaper, which determines its scope. It is indispensable in works where high requirements are not imposed on the technical indicators of materials, since its cost remains attractive. It should be noted that more expensive, purified quarry sand is a good alternative to river sand when used in concrete mixtures, which is due to the uneven shape of grains that have good tenacity compared to smooth particles.

Important characteristics of quarry sand are:

density - bulk and true;
voidness - determines the percentage composition of air in the total volume of bulk material;
sand grain size modulus indicating a certain group of material;
percentage of foreign inclusions, including clay, organic and dusty;
humidity;
frost resistance;
radioactivity;
filtration coefficient.

What is the density of quarry sand

From the entire list specifications considered building material can be distinguished:

bulk density of quarry sand (kg / m3), determined for conditions of natural humidity;
true grain density (g/cm3).

Bulk density refers to the weight of one cube of bulk material in an uncompacted state. This includes not only the volume of solids, but also the voids between them, so the bulk density of coarse sand is always less than the corresponding values related to fine-grained materials. In the first case, for example, the average density of sand extracted from a quarry is 1400-1500kg/m3, and in the second case it is 1700-1800kg/m3.

The bulk density of bulk building materials is often called average, which is not entirely true, since the term "average density" refers more to solid and liquid media.

The true density of the material is a constant value depending on the structure of the sand grains and their chemical composition. Based on the technical conditions presented in GOST 8736-2014, the indicator of the true density of sand grains of natural sand should be in the range of 2-2.8 g / cm3. Material with such values is introduced into the composition of mortars, concretes and dry mixes, it is used in the construction of foundations under roads and runways.

The density of quarry sand determines its consumption for the performance of certain works. With the same volume of material and a lower indicator of its density, you will need to purchase less sand in weight equivalent. In other words, with a bulk density of 1400 kg / m3 - in one cube there will be 1.4 tons of sand, and with an indicator of 1800 kg / m3 - 1.8 tons of sand. But with a lower density of the material, it will be necessary to take into account its greater voidness, which can affect shrinkage when compacting the sand layer or increase costs when buying binders that are part of the concrete mixture. Do not forget that the density of sand is affected by its humidity and the presence of clay impurities. These factors degrade the quality of the bulk material.

Methods for determining density

Possible methods, their essence, required equipment and tools for measurements are indicated in GOST 8735-88. It also specifies the stages of testing and methods for processing the results.

The bulk density of sand is determined by weighing it in measuring cylindrical metal vessels. Their capacity is 1dm3 and 10dm3. The first vessel is intended for dried and sifted, and the second for unsifted sand, which is in its natural state at normal humidity. Empty and full containers are weighed, after which the value of the bulk density of sand is determined by the formula.

In domestic conditions, an ordinary 10-liter bucket is used, into which sand is poured from a height of about 10 cm until the “heaped” vessel is filled. Next, the elevation is cut flush with the edge of the bucket, and the sand that fits into the container is weighed and its net mass without a bucket is determined. The result obtained in kilograms is divided by 0.01 m3, which allows you to find out the bulk density of sand, or the mass of one cube of material in tons.

In the laboratory, two methods are used to determine the true grain density:

pycnometric - using a pycnometer, which is a glass vessel of a special shape and a certain capacity;
accelerated - using the Le Challier device, which has a peculiar shape with a funnel in the upper part and a scale printed on the neck of a glass vessel.

The preparation and conduct of tests are thoroughly described in the above GOST. The methods for determining the true density differ significantly from each other, and the processing of the results is carried out according to completely different formulas. But in the end, the figures are identical, although the duration and complexity of the processes vary markedly.

How to improve the characteristics of quarry sand

The qualitative composition of bulk material is improved in two ways - sifting and washing. During processing, large debris and stones are removed, as well as clay and organic inclusions. Seeded sand is more homogeneous and in most cases is already suitable for mixing foundation and plaster mortars.

Washed sand, as the name implies, is cleaned with a large amount of water. As a rule, the process takes place in the conditions of flooded quarries, but if it is necessary to process sand in dry conditions, its composition is improved by additional arrangement of water reservoirs. As a result of cleaning, almost all clay inclusions are washed out of the sand, and the quality of the material approaches a cleaner river analogue.

Alluvial sand is allowed to be used in critical monolithic structures and in the production of durable concrete.

The use of different compositions of quarry sand

The purpose of the material in question depends on its quality, the presence or absence of impurities. For example, low-quality quarry sand, due to its low cost and versatility, is widely used in several areas that are not always associated with construction. In particular:

to "lighten" the soil layer in agricultural work;
when arranging embankments in low-lying or swampy areas;
in landscape design;
in road construction;
at treatment facilities;
as backfilling of trenches or when filling ditches;
when storing vegetables;
for domestic and household purposes - for growing seedlings and flowers, sprinkling icy paths, etc.

Seeded sand, extracted from quarries, is used in finishing work, laying it in the composition of plaster and cement mixtures. The material is allowed to be used in the construction of foundation pads and asphalt pavements. Fine-grained fractions show themselves excellently as part of the initial putties, various grouts and decorative mixtures. Coarse-grained quarry sand is laid as a drainage layer and added to the solutions during pouring curbstones and paving slabs.

Alluvial sand is intended for concrete and reinforced concrete structures responsible for the bearing capacity of buildings. It is introduced into the composition of dry building mixtures for various purposes.

You should not bet on the economical purchase of low-quality sand if more expensive material is required for work. Having received a one-time benefit, you can acquire a whole range of problems that will have to be solved for many years.

The first plan is the issue of acquiring materials. To calculate how much sand to buy for mixing the required volume of masonry, you need to know the density of the bulk component. This indicator significantly affects the strength parameters of structures and buildings. The conversion of mass into volume (and vice versa) is also carried out because the price of the material is indicated in different ways: per weight or volume unit.

What is density and what does it depend on

This is a physical characteristic of a substance, showing the mass of its unit volume and expressed in g / cm3, kg / m3, t / m3. Sand, like all bulk materials, has the following feature: depending on the conditions, the same amount of sand can occupy a different volume. The density index of building sand is influenced by the following factors.

1. Grain size (fineness modulus). Sand is a mixture of particles ranging in size from 0.14 to 5 mm, formed naturally during the destruction of rocks. How smaller size grains and the more homogeneous the composition, the denser the sand. Coarse and medium-grained material is used for the manufacture of concrete, fine-grained - for cement mortars, fine-grained (pulverized) - for building fine mixtures.

2. Porosity and level of compaction. They characterize the number of voids in the bulk material. In a loose state, building sand has a porosity of about 47%, in a dense state - no more than 37%. Looseness is reduced due to saturation with moisture, vibration, dynamic effects. Porosity is estimated using a special coefficient e: for fine-grained sands of dense composition, it is about 0.75, coarse and medium-grained - 0.55. The compacted sand mass takes on fairly high loads and distributes the stress that occurs in the foundations well.

3. Humidity. Usually, reference books give density at a normal humidity level, regulated by GOST. When buying, it should be borne in mind that the weight of a cubic unit of raw material differs significantly from the theoretical indicator. With an increase in humidity from 3 to 10%, the grains of sand are enveloped in water - due to this, the volume increases, and the density, respectively, decreases. With further moisture saturation (up to 20%), water displaces air and fills the voids between the grains - while the weight of a cubic meter increases.

4. The presence of impurities. Sometimes particles of clay, dust, salt, mica, gypsum, humus, crushed stone, stone chips are contained. They affect the quality characteristics of the building material: if for pure sand it averages 1,300 kg / m3, then for clay - 1,800 kg / m3. Sand can be cleaned by washing with water, but this increases its cost.

Types of density

Building sand can be characterized using different indicators of its volumetric weight: theoretical and actual.

1. True (former name - specific gravity). This is the mass of a cubic meter in an absolutely compacted state, without taking into account between particles. The true indicator is determined in a complex laboratory way, its value corresponds to the weight of a cubic meter of solid non-metallic sandy rock - approximately 2500 kg / m3.

2. Medium (bulk). When determining it, it is taken into account that the calculated volume includes not only grains, but pores and voids that fill the gaps between them. The average is usually below the true value.

To independently determine the average density, use a bucket with a capacity of 10 liters. Sand is poured into it from a height of 10 meters until a hill forms - it is carefully cut horizontally at the level of the upper edge of the bucket. The material that fits in the container is weighed, and then its density is calculated in kg / m3: divide the mass in kg by 0.01 (the volume of the bucket in cubic meters).

The true value is a constant value and has an auxiliary value. In order to competently conduct construction, make practical calculations and evaluate the quality of the purchased material, it is more important to know the average. For example, if a cubic meter weighs less than 1300 kg, this indicates in large numbers voids and requires their filling with a binder. At the same time, the cost of materials increases, making construction more expensive.

The approximate indicators of bulk (average) density indicated in the table will help you purchase sand with the necessary parameters, quickly switch from weight to volume, and calculate the weight fractions of the mortar.

The average density of sand is an important indicator on which the performance properties of the substance and the future parameters of the concrete building mixture, the strength and stability of buildings, as well as the possible consumption of raw materials directly depend. It shows how much sand is contained in one unit of volume, which is taken as a cubic meter (1 m3).

This parameter is closely related to such material indicators as voidness and moisture, the degree of compaction and porosity. The features and correctness of the measurement of parameters can also introduce a certain error into the final result. Between these factors there is the following relationship: the greater the void between the particles and the moisture content of the substance, the smaller the bulk characteristic and the less pure sand fits in a cubic meter. This rule is identical for humidity, but with the opposite sign - due to the adhesion of fractions, the wet building material is compacted.