Drainage systems are created to remove and subsequently collect rain or groundwater from the site. If drainage is not carried out, the soil becomes swamped, and moisture quickly destroys the foundations of buildings. At the same time, dampness often appears inside buildings with all the ensuing consequences. In order for the system to work effectively for a long time, you need to choose the right crushed stone for drainage.
Functions of crushed stone in the drainage system
Crushed stone and gravel are used to create a drainage system. But the former has more advantages related to the shape of its particles.
Gravel is a material of natural origin. Its formation occurs naturally during weathering processes.
Crushed stone is produced by mechanical crushing, achieved through the use of special equipment. Because of this, its surface is rough and its shape is angular. Production technology allows you to obtain material of different grades, having specific sizes separate factions.
The gravel backfill settles over time, which reduces the distances between individual stones, which prevents quick and efficient drainage of the area. Also, the material almost always contains various impurities. They reduce the drainage properties of the bedding and clog perforated pipes (if they were used when installing drainage).
Crushed stone does not have the considered disadvantages. In addition to its drainage function, backfill also improves the load-bearing characteristics of the soil. It better resists external influences without sagging.
Crushed stone bedding is also intended for the following:
- partial filtration of water entering the drainage system;
- obstruction rapid siltation pipes;
- drainage of groundwater, rain and melt water.
Well-cleaned crushed stone from impurities is quite expensive. Therefore they use in practice different compositions bedding. Sand is most often used with crushed stone. This is done in layers: first, 10 to 15 cm of stone are poured, and then a sand backfill is made with the same thickness.
Types of crushed stone suitable for backfilling
Crushed stone is classified according to different parameters. One of them is the type of rock used to produce it. According to this criterion, the following types of material are distinguished:
- gravel;
- slag;
- granite;
- secondary;
- calcareous (dolomite).
To determine which crushed stone is needed for drainage from the types listed above, you should understand the characteristics of each type of material.
The most durable and frost-resistant is granite look. Such properties determine the possibility of long-term use of this building material (at least 40 years).
The disadvantages of the granite variety include:
- the presence of a radioactive background of natural origin;
- high price.
When purchasing granite crushed stone, you should ask the seller for a certificate. It indicates the class of radioactivity of this material. Normally, its value should be less than 370 Bq/kg.
The gravel type of stone is affordable. It also emits less background radiation than granite material. But it is inferior in strength.
Crushed dolomite stone is relatively cheap. It is obtained from rocks of sedimentary origin. This material dissolves with water, thereby causing liming of the soil, and already at minus 10 degrees it cracks. In terms of load-bearing properties, limestone stones are approximately two times inferior to granite stones.
The cheapest is the secondary type, which is the result of recycling concrete and brick.
The slag variety is generally a departure from metallurgy.
The optimal option for drainage properties is granite, and the average option is gravel and lime. Slag and secondary varieties are not recommended for use.
As a result of crushing various rocks, crushed stone products of five main fractions are obtained. Each of them has a certain range of sizes of individual stones, which determine the properties of the backfill.
The table below shows the division of fractions by size.
Medium is the optimal crushed stone fraction for drainage. Larger stones are used much less frequently. Sand is replaced with screenings.
The video below shows the process of creating a drainage system with crushed stone backfill.
Drainage systems consist of channels, wells, pipes, crushed stone or gravel backfill, which is protected from silting, for example, using geotextiles. It is recommended to backfill with medium-sized stones from 20 to 40 mm. Suitable species The crushed stones are gravel, dolomite and granite.
An integral element of the design of drainage systems is a crushed stone backfill. This material is an important component in the proper functioning of drainage. Crushed stone is made from various rocks, which are crushed into stones of various sizes.
Feature of granite crushed stone
To extract granite crushed stone, high-hard rock 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 frost;
- greater strength - 1 cm of the substrate is virtually not damaged by the action of a mass of 100 tons;
- relatively high density. In the embankment it is equal to 1.4 t/m?. According to this characteristic, crushed granite stone is superior to other analogues.
Granite crushed stone has a number of specific advantages.
- A drainage system with a filling of this material helps 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 that is obtained by crushing hard rocks. It does not contain clay fragments, dust, or other particles that can be washed out with water. Based on this, granite crushed stone is a reliable filtration material and with its help, for example, drainage of a septic tank is arranged.
- The process of obtaining material by crushing promotes the formation of angular stones, which adhere well to each other. That's why it doesn't move.
- Granite crushed stone is harmless to humans; it belongs to the first safety class.
- Its price is higher when compared with analogues made from other materials, but this type of backfill pays for itself due to its high-quality features and long service life. When constructing a drainage system closed type the use of this material brings significant savings, since cleaning of the structure occurs very rarely.
Advice! Regardless of the advantages, crushed granite stone cannot be called perfect in use. The greater strength of the material also has a downside - so that the stones do not push through drainage pipes, the latter must be wrapped in a protective bandage. In addition, from time to time granite quarries have an increased background radiation, so the resulting crushed stone must be monitored with a dosimeter.
Properties
Crushed gravel differs from granite in that it is created by crushing sedimentary, inorganic rocks, and therefore its structure is loose. The gravel stones are round in shape. Crushed gravel has the following properties:
- The frost resistance of gravel material is high, but 2 times less than that of granite. The stone itself is not afraid of frost, but impurities cannot withstand temperatures below –20? C. In severe frosts, the material cracks, and the substrate becomes dusty;
- high strength - the layer does not collapse under a load of 80 tons;
- clay fragments account for 0.6%;
- not strong rocks are contained in the amount of 1.5%.
Advice! Compared to granite, crushed gravel is less durable, but its price is more affordable. In addition, from the standpoint of environmental friendliness, it is less radioactive, and therefore more reliable.
Despite the fact that gravel material is also crushed, like granite, the corners of its stones are sharper, so crushed stone filters better.
Advice! The looseness of the material plays a negative role, since clay fragments will be washed out of it. This, naturally, will lead over time to clogging of the perforated pipes, causing the throughput properties of the drainage system to deteriorate, and this, in turn, will lead to the need for its frequent cleaning.
Crushed gravel works well when draining an area, so it is better to use it as foundation drainage rather than for making concrete. When laying the foundation, it is additionally necessary to add a sand base of sand, the layer thickness of which must be 0.1 m. Then the sand will take over part of the negative influence water on the foundation, and this factor will be felt to a minimum extent.
Use of dolomite crushed stone
The origin of dolomite crushed stone is not much different from granite. It is mined using the same methods and differs little from its granite counterpart - dolomite material contains calcite in its composition. In addition, impurities in the rock in the form of quartz and iron oxide give the material various shades - from gray to brown, which makes this stone visually attractive.
Dolomite stone is different:
- low frost resistance. Due to impurities, a lot of stone loses its properties at a frost of –10? C;
- instability of strength, which ranges for a 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 quite durable;
- clay contained in the material is 0.25%;
- inclusion of weak rocks forms 5%.
Dolomite crushed stone is relatively environmentally friendly, low price and relatively good strength.
Advice! The disadvantage of dolomite crushed stone is the presence of metals in the material, which form salts during oxidation. As a result, crumbs are formed under the influence of its own weight.
Factions
Depending on the size of the stones, the crushed stone fraction is divided into two types.
- Screenings up to 0.5 cm in size. It is not suitable for drainage, because such fragments are easily washed off drainage waters.
- Stones measuring from 0.5 to 2 cm are not used for drainage, since such fragments are expensive and are used in construction work cement structures.
- Fractions from 2 to 4 cm are most in demand for drainage. Such stones are relatively inexpensive and are used for drainage.
- The category ranging in size from 4 to 9 cm can also be used for the drainage system, but when filling the material into the trench, an excavator is used.
- Fractions from 9 to 30 cm are decorative stones. They are interesting only as elements of landscape design.
Crushed stone of various origins and fractions has its own purpose in construction work. For the installation of a drainage system it is possible to use various material, but crushed stone of the middle fraction is more suitable.
A properly designed drainage pipe system will prevent moisture from penetrating into the building, erosion and pressure on the load-bearing foundation and the entire structure as a whole. The principle of operation of underground collection and drainage of water is based on its entry into receiving pipes (drains) through joints, holes or cracks in the walls.
This supply occurs due to the difference in water pressure provided by the depth of installation of system elements below the water level. The calculation of such depth, quantity and types of materials for the entire structure is based on the indicators of the “wettest” periods of the year - autumn and spring.
Most often, a horizontal system is used with a regular arrangement of tubular cavity drains with aggregates (crushed stone or gravel for drainage). In order to receive groundwater, holes are made in the walls of the pipes, where water flows due to the already mentioned pressure drop.
Crushed stone and gravel for drainage - the main differences
What is filler used for in tubular elements? Its purpose is to prevent them from silting, in which case it performs a filtration function. According to the rules, drains are laid in trenches prepared in advance according to the design, at the bottom of which there is a sand cushion no thinner than fifteen centimeters, and on top of it is the same layer of crushed stone or gravel.
All components are installed from above: geotextiles (if used), pipes, couplings and angles (other shapes), wells (drainage and collector with check valve), after which you should backfill with crushed stone and earth. For the correct functioning of the entire lead complex excess moisture It matters what kind of crushed stone is used for drainage.
As is known, gravel consists of rounded fragments of rock or minerals different sizes. It is generally accepted that gravel fragments can reach twenty millimeters. In this case, small (up to three millimeters), medium (up to ten) and large fractions of the material are distinguished.
Unlike gravel crushed stone has the appearance of acute-angled fragments of the same rocks or minerals. Its elements, which can reach one hundred millimeters, are obtained by crushing natural or artificial stone and other materials.
For the purpose of removing moisture using a drain system, it is best to use fractional material (gravel or crushed stone) with a fraction size of twenty to forty millimeters.
Crushed stone for drainage - conditions of use
It must be taken into account that only well-washed material can be used. The same applies to coarse sand for base cushioning in trenches. Flushing is mandatory to reduce siltation of the entire system. After laying and installing pipes with filler, backfilling with a layer of crushed stone or gravel of the required fraction, the drainage is covered with fabric geotextiles, over which the previously excavated soil is filled.
In this case, it is important to ensure the installation slope for natural moisture drainage towards the system wells. The layer of crushed stone top filling also depends on the characteristics of the soil in which moisture removal is arranged. And the denser the soil, the thicker the backfill will be required.
The entire designed system must collect water in a special well located at the lowest point of the relief plan. Its design includes the ability to receive maximum quantity moisture determined during the above “wet” periods of the year. If necessary, several wells can be made. By the way, experts advise using water from such wells for irrigation.
High soil moisture on the site or the presence of groundwater lying in its upper layers can cause significant damage to the house. Washing and wetting the foundation will sooner or later lead to its destruction. Following this, the walls will begin to get wet, and this is a direct threat to a comfortable life.
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| fraction 5 20 | fraction 20 40 | fraction 40 70 |