What is suitable for drainage is gravel or crushed stone. Crushed stone for drainage fraction

An integral part of the design of the drainage system is crushed stone. This material is an important component in the proper operation of the drainage. Crushed stone is made from different rocks, which are crushed into stones of different sizes.

Characteristics of crushed granite

For the extraction of crushed granite rock, a rock of high hardness is first blasted, then crushed and sieved. It has the following properties:

• extremely high frost resistance. The material can serve for an unlimited time, since it is not destroyed by any frosts;
• high strength - 1 cm of the substrate is practically not damaged by the impact of a mass of 100 tons;
• relatively high density. In the embankment, it is equal to 1.4 t/m³. According to this characteristic crushed granite surpasses other analogues.

Granite crushed stone has a number of specific advantages.

• A drainage system with a filling of such material serves for a long time, since the boundary crushed stone is durable and hard.
• Since the material is frost-resistant, nothing will happen to it in open-type drainages.
• Granite crushed stone is a homogeneous material, which is obtained by crushing hard rocks. It does not contain clay fragments and dust, as well as other particles that can be washed out with water. Therefore, crushed granite is a reliable filtration material and is used, for example, to drain a septic tank.
• The process of obtaining material by crushing contributes to the formation of angular stones that adhere well to each other. Because of this, he does not move.
• Granite rubble is harmless to humans, it belongs to the first class of safety.
• The price for it is higher compared to analogues from other materials, but this type of backfill pays for itself due to its quality characteristics and long service life. When constructing a closed-type drainage system, the use of this material brings tangible savings, since the cleaning of the structure occurs very rarely.

Note! Despite the advantages, granite crushed stone cannot be called ideal in use. The high strength of the material also has a downside - so that the stones do not push through the drainage pipes, the latter must be wrapped in a protective bandage. In addition, sometimes granite quarries have an increased radiation background, so the purchased crushed stone must be checked with a dosimeter.

Properties

Gravel crushed stone differs from granite in that it is produced by crushing sedimentary, inorganic rocks, so its structure is loose. Gravel stones are round in shape. Gravel crushed stone has the following properties:

• frost resistance of gravel material is high, but 2 times less than granite. The stone itself is not afraid of frost, but impurities cannot withstand temperatures below -20ºС. In severe frosts, the material cracks, while the substrate becomes dusty;
• high strength - the layer does not collapse under a load of 80 tons;
• clay fragments make up 0.6%;
• weak rocks are contained in an amount of 1.5%.

Note! Compared to granite, crushed gravel is less durable, but its cost is more affordable. In addition, from the point of view of environmental friendliness, it is less radioactive, therefore it is safer.

Although gravel material is also crushed, like granite, the corners of its stones are sharper, so such crushed stone filters better.

Note! The friability of the material plays a negative role, since clay fragments will be washed out of it. This, of course, will lead over time to clogging of the perforated pipes, causing the throughput of the drainage system to deteriorate, and this in turn will lead to the need for frequent cleaning.

Crushed gravel performs well when draining the site, so it is better to use it as foundation drainage, and not for making concrete. When constructing the foundation, it is additionally necessary to add a sandy substrate of sand, the layer thickness of which should be 0.1 m. Then the sand will take on part of the negative effect of water on the foundation, and this factor will be felt to a minimum degree.

The use of crushed dolomite

The origin of crushed dolomite is not much different from granite. It is mined by the same methods and is slightly different from the granite counterpart - calcite is present in the dolomite material. In addition, impurities in the rock in the form of quartz and iron oxide give the material different shades - from gray to brown, which makes this stone visually attractive.

Dolomite stone is different:

• low frost resistance. Due to impurities in large quantities, the stone loses its properties at a frost of -10 ºС;
• instability of strength, which varies for the substrate from 50 to 150 tons per 1 cm. Strength depends on the amount of certain impurities. Brown crushed stone, characterized by a high metal content, is strong enough;
• clay is contained in the material 0.25%;
• the inclusion of weak breeds is 5%.

Dolomite crushed stone is characterized by comparative environmental friendliness, low cost and relatively good strength.

Note! The disadvantage of crushed dolomite is the presence of metals in the material, which form salts during oxidation. As a result, under the action of its own weight, a crumb is formed.

Factions

Depending on the size of the stones, the crushed stone fraction is divided into several types.

• Screenings up to 0.5 cm in size. It is not suitable for drainage, since such fragments are easily washed away by drainage water.
• Stones ranging in size from 0.5 to 2 cm are not used for drainage, as such fragments are expensive and are used in the construction of concrete structures.
• Fractions from 2 to 4 cm are most in demand for drainage. Such stones are relatively inexpensive and with their help drainage is arranged.
• The 4 to 9 cm category can also be used for the drainage system, but an excavator is used when backfilling the material into the trench.
• Fractions from 9 to 30 cm are decorative stones. They are interesting only as elements of landscape design.

Crushed stone of different origin and fractions has its purpose in construction. Different materials can be used for the device of the drainage system, but crushed stone of the middle fraction is best suited.

Garden and household plots, located on clay soils, suffer from an excess of moisture, turn into a real swamp after rain or snow melt. A similar situation is observed on light soils if there is no natural runoff.

To protect the site from the harmful effects of rain and melt water, a well-executed drainage system is required. It is also required when groundwater lies closer than two and a half meters. On the lower reaches with clay soil, a drainage system is made throughout the site and around the house.

The drainage device can be entrusted to specialists or, having acquired all the required materials, design and lay it yourself. The main thing is to choose the right gravel, which is the basis of drainage, ensures the smooth operation of the system for decades.

Pipes (drains) laid during the arrangement of drainage on the site are made with holes through which water enters the drainage. The presence of various large particles and sludge in the liquid is unacceptable. If the holes become clogged, the system will stop functioning.

To purify water from "dangerous" impurities, the base of the drainage system is laid out with crushed stone, which acts as a kind of filter. The rough surface and angular shape of this crushed bulk material prevent silt and other impurities from entering the drain.

The location of the crushed stone depends on the type of drainage communications network. In open systems, they lay out the bottom of the trenches and strengthen the walls, and in closed systems they cover drains from all sides. This is the reason for the importance of choosing the right material for arranging the filter layer.

Crushed stone: types and fraction

The initial raw material in the production of crushed stone is various rocks, waste from the mining and construction industries. Thus, there are three main types of this bulk material:

• granite;
• gravel;
• dolomitic.

Granite is considered the best for drainage, an alternative to which can be more affordable, but less durable gravel. Lime, that is, dolomite, is cheap, but not very suitable for drainage, it is used mainly in construction.

The size of the grains into which the feedstock is crushed determines one of the most important characteristics of crushed stone - the fraction. It is measured in millimeters and defines another classification of the material.

There are five groups of crushed stone by fractions:

• screening (less than 5 mm);
• small (5-20);
• medium (20-40);
• large (40-70);
• non-standard (up to 120).

And if the choice between granite and gravel rubble is due to the budget provided for the organization of drainage, then the requirements for the fraction are much stricter.

The importance of crushed stone size for the drainage system

High requirements for the fraction of stones used to equip the filtration layer are due to the need to ensure the throughput of melt, rain, groundwater, but at the same time retain silt and other particles that can clog the holes of the drainage pipes. And if the size is chosen incorrectly, various kinds of problems may arise, leading to disruption of the drainage system on the site:

Small rubble. A layer of grains with a size of 5 to 20 millimeters is characterized by too small voids. Water through such "holes" will simply seep through. This will slow down the filtration process, and, consequently, the drainage will no longer drain the accumulated volume of water in a timely manner.

Large rubble. Filtration of drainage from pebbles, the size of which varies between 40-70 millimeters, on the contrary, is characterized by the presence of large voids. Water does not ooze through such a layer, but passes at a rapid speed. A fast "current" begins to erode the soil. The result is a flooding of the drainage, which completely fails.

Thus, neither coarse nor fine fraction is suitable for drainage.

What fraction of crushed stone is suitable for drainage?

The most optimal size of voids between the stones of the filter layer is formed by the middle fraction, that is, crushed stone, the grain size of which is from twenty to forty millimeters. It has an affordable cost, perfectly purifies water in both closed and open systems, and prevents drainage from flooding.

There is another type of crushed stone, which can also be used in the arrangement of a drainage system - screenings. Small stones, whose dimensions do not exceed 5 mm, can be used for the underlying layer of the drainage trench. They can become a substitute for expanded clay or sand.

The amount of crushed stone of the middle fraction is determined by the thickness of the filtration layer. This parameter depends on the density of the soil on the land. Regardless of this, the thickness of the laid rubble cannot be less than thirty centimeters.

Departure from the general rules

There are situations when the design of the water drainage system allows the use of a gravel size other than the recommended one:

• Deep drain

This is a system laid to a depth of more than 80 centimeters. Here it is permissible to use a large fraction, that is, with grains from 40 to 70 millimeters. This does not mean that the average crushed stone is not suitable. It can be used too. But if the master has only coarse-grained material at his disposal, then it is suitable for drainage, which will allow you not to spend money on buying other gravel.

• The impossibility of bringing the channels to the site of lowering the soil

This problem is due to the peculiarities of the landscape. If it occurs, then the best option is to equip a sewer drainage well. It is covered with crushed stone of a large fraction, on top of which geotextiles are laid. So that such a design does not spoil the overall appearance, it can be disguised as a flower bed.

With the exception of these two specific situations, it is recommended to use crushed stone of medium fraction for the drainage system.

In an effort to figure out which crushed stone is better for drainage of a construction site, we very often go to extremes, preferring economically unprofitable options for backfilling. Meanwhile, the choice of the “correct” variety of crushed stone allows you to save on the arrangement of the drainage system.

Therefore, in this article we will determine the composition of the drainage backfill. We will offer our readers several options for fractions and several varieties of rocks suitable for the manufacture of the product we are interested in. Moreover, when choosing the “correct gravel”, we will take into account the “interests” of both drainage systems and building foundations.

The introduction of crushed stone or gravel immediately improves two characteristics of the supporting soil - drainage and bearing capacity. The first characteristic is responsible for the volume of moisture passed through the soil layers, and the second for the ability to resist external pressure without subsidence of the soil.

As a result, gravel or crushed stone bedding is used not only in the arrangement of the drainage system, but also in the process of building the foundation. Moreover, in the first case, such bedding “works” as a filtering barrier, partially cleaning the drains, preventing the drainage pipe from silting up and “conducting” atmospheric and groundwater to the sewage main.

In the second case - during the construction of the foundation - the backfill "corrects" the insufficient bearing capacity of the supporting soil, simultaneously removing excess moisture from the base of the foundation. That is, due to the introduction of bedding into the pit, it is possible to change the bearing capacity and influence the magnitude of soil heaving deformations, which are directly related to soil moisture.

At the same time, the compositions of drainage and supporting beddings can be different. After all, “clean” crushed stone or gravel is not cheap.

Therefore, the backfill is formed from sand-gravel or sand-gravel mixtures, laying these materials in layers: 10-15 centimeters of crushed stone or gravel and 10-15 centimeters of sand.

What gravel is needed for drainage?

Crushed stone is a product of rock processing. It is produced from large fragments of rocks using special crushers. Accordingly, this method of production allows you to "produce" crushed stone from the rock of certain varieties, with a strictly controlled "caliber" of the fraction.

Another advantage of crushed stone is a rough fault line. After all, this product was created artificially (in a crusher) And this quality increases the “filtering” ability of the drainage system. The chipped, rough surface of rubble literally attracts dirt particles.

According to the type of rock used in the production of crushed stone, this product is divided into the following varieties:

• Granite crushed stone is the most durable, frost-resistant and durable option that can be used for up to 50 years, in the most severe conditions (with any soil acidity). But granite has two drawbacks. Firstly, this breed has a natural radiation background (which deters some buyers). Secondly, granite is very expensive. But the high price is justified by phenomenal strength (a centimeter bedding can withstand about 100 tons of load) and enviable frost resistance (granite does not crack at any temperature).
• Dolomite (lime) crushed stone is the cheapest option that does not emit radiation and is absolutely inert from the point of view of environmentalists. But dolomite will “live” in difficult soil for no more than 15 years. Therefore, they try not to use crushed limestone for drainage of the foundation. After all, this material begins to crack at temperatures below -10 degrees Celsius. And the bearing capacity of a centimeter bedding is half that of crushed granite.

What gravel to use for drainage?

Gravel is a product of nature itself. This is the name of a mixture of small stones collected in quarries, riverbeds and on the shores of lakes or seas. A good example of gravel is river or sea pebbles.

Therefore, the main advantage of gravel is the low cost of the product. After all, it was created by nature itself. And the main drawback is the heterogeneity of the composition and "caliber" of the fraction. Typical gravel or crushed stone, obtained from large pebbles and rock fragments, contains about a percent of clay and sand and about two percent of weak rocks.

As a result, a centimeter bed of gravel or crushed stone can withstand about 80 tons of load, and at temperatures below -20 degrees Celsius, this material begins to collapse. Moreover, due to the smooth surface, gravel filters dirt very poorly and practically does not protect the pipe from silting.

Therefore, gravel and crushed gravel can only be used in drainage systems in combination with sand bedding, at least 10 centimeters thick. It will filter out particles of dirt and protect the pipe from silt.

How is the crushed stone fraction selected for drainage?

Usually, five fractions of crushed stone “come out” of the crusher:

• The first - with dimensions of fragments up to 5 millimeters. It is not suitable for drainage systems, since it contains all the screenings, which will simply be washed away by groundwater.
• The second - with fraction dimensions from 5 to 20 millimeters. It is not suitable for the drainage system for a completely different reason - such crushed stone is in great demand in the construction and production of reinforced concrete products, so this product is not cheap.
• The third - with a "caliber" fraction of 20-40 millimeters. This is perhaps the best type of crushed stone, from the point of view of drainage specialists. It is relatively cheap and does not contain screenings and dust.
• The fourth - with fragments ranging in size from 40 to 90 millimeters. This is also a good option, but due to the significant dimensions of the debris (up to 9 centimeters), it is practically not suitable for “manual” construction. Such crushed stone is poured into a drainage trench or into a pit by an excavator.
• Fifth - with dimensions from 100 to 300 millimeters. This is a decorative type of gravel. It is not used either in the production of reinforced concrete or in soil drainage. Such rubble is only of interest to interior, exterior and landscape designers.

Drainage without crushed stone and gravel - is it possible?

Both crushed stone and gravel, of course, are necessary for both draining and supporting soil. However, these materials "weight" the construction estimate. And the cost of the drainage system, in the end, depends on what kind of rubble is used for drainage or what kind of gravel is used in the process of arranging such a "highway".

That is, if you refuse crushed stone or gravel, the drainage system will cost less than the “stone” counterpart. But what will such a refusal lead to? After all, crushed stone and gravel not only filter drains, but also reinforce the soil.

However, modern drainage without crushed stone sofrock works just as well as "stone" counterparts. The key to the performance of sofrock systems is a special drainage pipe with a diameter of 300 millimeters and a throughput of 110 millimeters. Moreover, the 95-mm shell surrounding the polymer core of the pipe is made of extruded polypropylene enclosed in a geotextile mesh.

As a result, in terms of strength and filtering ability, the sofrock system practically does not differ from drainage on crushed stone, and in terms of durability and frost resistance, such a system surpasses the “stone version” by several times.

High soil moisture in the area or the presence of groundwater in its upper layers can cause significant damage to the house. Washing and wetting of the foundation will sooner or later lead to its destruction. After him, the walls will begin to get wet, and this is a direct threat to a comfortable life.

fraction 5 20	fraction 20 40	fraction 40 70

Crushed stone for drainage - an indispensable element of the drainage system

The drainage system helps to ensure the removal of excess moisture from the foundation and significantly reduce its level in the soil on the site. Its scheme is based on the data of geodetic surveys. In order to prevent soil and dirt from getting into the drainage pipes, which can cause clogging and swamping of the entire system, a layer of sand is poured to the bottom of the dug trench and crushed stone is laid on top of it. Their thickness depends on the depth of the trench itself, but on average it is about 15 cm.

What gravel is needed for drainage

It all depends on the financial capabilities of the customer. One of the elements of the drainage complex can be crushed stone of any kind, without exception. Granite crushed stone has maximum strength and is able to withstand a large number of freeze and thaw cycles. With the right device, the system will last more than 40 years.

What type of crushed gravel to use for drainage

The best material for the drainage system is gravel. According to its physical characteristics, it is close to granite, but unlike it, it does not have a high radiation background. When choosing crushed gravel, it is better to dwell on crushed rock, and not on natural gravel: pebbles, which have a rounded surface. The task of the crushed stone is to prevent the penetration of dirt into the pipes. The ribbed surface of rubble copes with this task much better than smooth pebbles.

Fractions of crushed stone for the drainage system

It is better to filter water using fine fractions. Crushed stone with a size of 5 to 20 mm has a good flakiness, fits snugly to each other, ensuring the penetration of water into the pipes of the drainage system, leaving sand and dirt on its surface. Small gravel has the highest cost, if the budget does not allow it to be purchased, then you can buy an average stone with a particle size of 20 to 40 mm. When buying, you also need to clarify the level of flakiness and the degree of cleaning of gravel. A large amount of dust on the surface of the rubble can play a negative role and also lead to a quick failure and clogging of the drainage.

If your garden or garden plot suffers from an excess of moisture, is located in a lowland and turns into a swamp from the slightest rain or when snow melts in the spring, you need to think about drainage.

All troubles come from excess water, when the soil in the area is clayey, it does not pass water well. But even on light soils, water can remain for a long time if the site does not have a natural runoff. The drainage system will help you eliminate all these unpleasant circumstances if it is made in accordance with the technology.

For the basis of the drainage system, you need to choose the right gravel.

Drainage work must be carried out before you start arranging the site yourself or by inviting a specialist designer. Before embarking on a project, observe your site during the "high water" period: in the spring, during floods, and during heavy rains. This will help you determine the location, depth of the drainage ditch and select the right material.

You also need to know the geology of the site. If it is located in a low place with clay soil, drainage will have to be done throughout the site and around the house to protect the foundation. Remember: if the groundwater in your area is closer than 2.5 m, a drainage device is necessary.

It is not necessary to invite specialists to create it. The simplest drainage system can be done independently, spending only on materials.

If no mistakes are made at the design stage, then groundwater will no longer harm buildings, the soil will not be washed out, and the roots of plants will not rot. Those plants that do not like high humidity will develop well.

The basis of the drainage system is (in the literal and figurative sense of the word) crushed stone. Your task is to determine which type of gravel is suitable in your case. Do not be too lazy to familiarize yourself with the selected sample in advance before it is delivered to you at the site.

Depending on the material, crushed stone is divided into:

Crushed stone is granite, gravel, dolomite.

1. Granite. It is characterized by hardness, resistance to frost, durability. It will last at least 30 years, or even all 40. Although it is the most expensive of all, it makes sense to purchase it if funds allow. But at the same time, do not forget that granite is naturally radioactive. Make sure that the crushed stone that you are going to buy has the appropriate certificates and conclusions about its harmlessness to humans and is approved for use in residential areas.
2. gravel. The radioactive background is negligible. It is not as strong as granite, but with the same density when falling asleep and the same characteristics of the shape of stones (or grains), it costs less. The gravel can be natural rounded pebble stone or mechanically crushed rock from a quarry. The cost is about the same, for drainage the second option is preferable. Due to chips and sharp corners and edges, it filters out debris better and prevents the drainage ditch from silting up.
3. Dolomitic. Sedimentary rocks serve as material for it. Compared to other types, crushed stone for drainage is the most affordable. In addition, the most environmentally friendly, safe for humans, does not emit anything harmful. Its disadvantage is a relatively short service life - only 15 years. Yes, even if certain conditions are met. It needs dry, frost-free soil with low acidity.

If you want to avoid silting up the trench, make sure that the drainage gravel you bought is well washed.

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What fraction for stones to choose?

The fraction of crushed stone for drainage can be from 5 to 120 mm.

One of the main characteristics that you need to pay attention to when choosing crushed stone is the fraction or size of stones (grains). Depending on it, fractions are divided into several types:

1. "Sifting". This fraction is the smallest, the remnants of rock crushing up to 5 mm in size. It can replace expanded clay or sand at the bottom of a drainage ditch.
2. Small fractions - up to 20 mm. Such crushed stone is the most expensive of all factions, but also the most in demand. It is not very suitable for drainage: due to the fact that small grains are poured quite tightly, water can linger.
3. Medium - up to 40 mm.
4. Large - up to 70 mm
5. Non-standard - up to 120 mm.