Warm, even floors are a must for housing. Sometimes, for arranging the floor, an expanded clay concrete screed is used. A screed is made of cement and expanded clay. Despite the apparent fragility of the material used, the final base is reliable, strong and has heat and sound insulation qualities.
Characteristics of expanded clay
The main quality of expanded clay is lightness, which implies a significant reduction in the weight of the concrete screed. In apartment buildings, a significant load on the floors is undesirable, therefore, a concrete screed with expanded clay would be an ideal application.
In addition to being lightweight, the material has the following qualities:
- Porosity - this quality is responsible for light weight, noise damping.
- Strength - the material is fired in a kiln, which gives it extra strength.
- Environmental friendliness - expanded clay is made of clay or clay shale. A concrete screed with expanded clay meets this requirement, too, since the composition is completely natural.
- Resistant to fire, chemicals, moisture, decay and rust.
The lightness of the expanded clay layer justifies its use for leveling large differences in unevenness in houses, especially multi-apartment ones. The floor loads are less loaded and the efficiency is very high.
We must not forget about the disadvantages of screed using expanded clay. The coating will have to be sanded, the porous part will level the base in height, but the floor will be rough. Smoothness is achieved by using a grinder.
Despite certain difficulties in the work, the use of expanded clay is very justified - after pouring the screed, you can lay flooring of different types, from linoleum to tiles.
The composition of the screed with expanded clay
Expanded clay concrete screed is prepared based on certain proportions of the material. A good screed is obtained if medium or fine granules are used. Correctly selected fraction gives optimum weight, thickness and good distribution in the mixture.
The composition of concrete with expanded clay includes:
- Expanded clay, always moistened. The granules moistened with water are better distributed in the solution.
- The sand required for the solution is taken from the river, preferably cleaned of impurities.
- The cement added to the mortar can be of different grades and added in different quantities by weight.
The different weight of the cement regulates the strength of the screed.
Adding different amounts of cement to the composition gives different strength of the composition, but without sand, the concrete screed may begin to crack.
The sand gives the composition the necessary plasticity.
To mix the solution, take 3 parts of sand, 1 part of cement and 4 parts of expanded clay. Expanded clay is moistened with water, mixed, left for a while. Then the water is drained. Sand and cement are mixed separately. Mixing is carried out by adding a sand-concrete mixture to expanded clay, simultaneously adding water to obtain a plastic solution.
The proportions of the materials taken must be accurate, in this case a good end result is achieved. An accurate measurement of the weight of each material is essential. It is better if the required amount of solution could be easily divided by 7, since it is this proportional number that determines the quality of the composition.
When arranging a claydite-concrete screed with a height of 5 cm, 55 kg will be required. ready-mix for 1 sq. area.
Types of screed with expanded clay
The screed device has its advantages, because there are different options for the device. The appropriate method is determined based on the initial conditions available.
The types are as follows:
Screed with wet expanded clay
The wet method is characterized by the need to add expanded clay to the solution. Expanded clay interferes with the cement-sand mixture and is poured over the surface. The use of a composition made in a similar way is excellent for creating a screed that is large in thickness.
The weight of the cement composition is much greater than that of expanded clay-concrete, and therefore it is better to use a similar method to relieve pressure on the floors.
This method consists in the fact that first the floor is leveled with dry expanded clay. Further, the material is poured with a cement mixture made without the use of expanded clay. This method is used when it is necessary to make a screed of considerable thickness, for example, more than 10-15 cm.
Dry screed method
Dry screed eliminates the use of concrete mortar. Only expanded clay is used. The material is poured into cells made of bars and carefully leveled. The use of this method makes sense if the floor surface is easy enough to level. The height of the layer should have a small size of 2-5 cm. The finished layer is covered with plywood or plasterboard sheets.
The dry method is preferable to use by craftsmen with little experience in construction work. The method does not involve the use of cement, the installation is quite simple and fast.
The first 2 methods are able to create a high-quality foundation, but they are quite capricious in application.
It is necessary to know how to make a solution, what nuances must be observed when pouring, to know the degree of drying. The finished, dried surface must be sanded, this step is to achieve the smoothness of the floor.
If the finished floor sticks to the surface, no sanding is necessary. The roughness of the coating provides better adhesion to the finished, finished floor. True, the consumption of glue may slightly increase.
How long does a screed with expanded clay dry
The dry method of expanded clay screed is valuable in that it does not sometimes take valuable time. The floors are easy to install and ready to be finished right away without waiting to dry. But this method cannot always be applied. When it becomes necessary to use expanded clay with concrete, you need to know.
The screed dries up depending on the method used. Expanded clay granules, mixed into the solution, dry for a long time. The poured floor must be covered with polyethylene and periodically soaked. Thanks to water, the solution gains the necessary strength and prevents the coating from cracking.
When pouring the screed, beacons are often used. They must be removed from the solution approximately 2-3 days after pouring. For about a week, the floor must be moistened with water and be sure to cover it with foil. 2 weeks after pouring, the coating can be used to lay the finished floor. Complete drying will take place only 4 weeks after pouring.
A screed using expanded clay, poured in a combined method, dries faster due to the small thickness of the concrete. After pouring the concrete, the floor is left under the film for a day, after this time the beacons are removed, and the floor is moistened with water. After a week, the floor can be sanded and finished.
The combined screed dries completely after 2 weeks. It is convenient in that the coating does not need to be spilled with water.
Preparation of a rough base using expanded clay significantly lightens the load on the floors, so this type can be used in different houses. One of the qualities of the material is its soundproofing ability, which means that the sound conducted by the floor covering can be significantly reduced. For laying the screed, it is necessary to use high-quality materials and good expanded clay. For stronger isolation from sounds, you need to do.
Currently, there are many different technologies for flooring. Among them, one of the popular options is. The use of expanded clay in the field device is economically beneficial in absolutely all respects.
Expanded clay concrete is a versatile material. Fired clay is used for its manufacture. It can be used not only in construction, but also in the insulation of walls and floors. The best effect can be achieved when using expanded clay as the first floor in private and multi-storey buildings. If we talk about its characteristics, then such a screed has similarities with cement-sand, differing in thermal insulation properties and less weight. This is what allows you to reduce the load on the foundation. Thanks to the clay used in the manufacture, expanded clay received a lot of positive properties:
- high resistance to aggressive media;
- economy in use;
- environmental friendliness;
- light weight;
- fire safety.
Among other things, expanded clay does not rot at all and does not corrode.
Features of using expanded clay
Expanded clay concrete can be used not only for, but also for wooden bases. If you plan to insulate a reinforced concrete floor, you can use expanded clay of any type and fraction, since in this case the weight does not affect the strength of the building.
Screed and insulation with the help of ceramic granules helps out perfectly when finishing the subfloor on the ground, which causes difficulties for many. For this, the earth cover is carefully leveled and equipped with high-strength waterproofing, which is used as a mastic, laid in several layers. The result is a solid, high-quality and durable base on which any floor covering can be laid.
If expanded clay concrete is used when arranging the floor of the first floors of wooden buildings, one should not forget about additional insulation. To do this, you can use foamed clay, which is mixed with a cement-sand composition. A moisture-resistant material is first placed on the boards of a wooden base, and waterproofing is applied on top of it and expanded clay concrete is poured.
Screed rules
Important! The screed with granules of various sizes allows you to obtain high-quality floor insulation with a small load on the base of the structure.
Floor insulation using expanded clay concrete can be done independently or entrusted with the work of specialists.
Preparatory work:
- Preparation of the base. This includes the mandatory cleaning of the surface from dirt, followed by the application of a universal primer. This will make the substrate resistant to mold and mildew. In addition, the primer will increase the adhesion of the floor to the material used for the screed. In this case, with expanded clay concrete.
- A vapor-waterproofing layer is placed on top of the prepared base. For this purpose, it is best to use construction mastic. If it is not possible to get it, the mastic can be replaced with reinforced polyethylene, the connection of which is carried out by means of heat treatment. The wires that are planned to be mounted in the screed must be laid in advance in boxes or corrugation.
To work, you need to prepare in advance all the necessary tools and materials:
- mixer;
- spatulas;
- building level;
- container for solution preparation;
- expanded clay;
- cement;
- water.
Marking the future coverage
At the end of the preparatory work, you can start marking the coverage. For this, a building level is used, with the help of which the horizontal is determined and lines are drawn. They show to what level the screed will be located. Beacons must be installed along the lines. They can be made from a ceiling profile, metal corner or pipe.
The beacons are fastened using cement mortar. Therefore, the next stage, during which the base is covered with expanded clay, can be started no earlier than in a couple of days, since you need to wait until the solution is completely dry.
Filling the space with expanded clay
Expanded clay is necessary to fill the space between the installed beacons. This should be done up to a certain level, which should be 2 cm below the floor mark. Expanded clay is leveled with a wide spatula.
When pouring the solution, expanded clay granules can float to the surface. To avoid this, it must be well tamped and filled with cement "milk", which is a liquid diluted cement mixture. It envelops the particles of the granules, gluing them together.
Pouring cement-sand mortar
It is possible to start making a cement-sand mixture and filling the surface with it only the next day after processing expanded clay with "milk". A rule is used to level the mixture. This must be done at the level of the uppermost mark of the installed beacons. It is necessary to level the mixture with smooth movements, while changing the amplitude and angle of inclination. Puddles that may form during pouring must be smoothed out until they disappear completely. In carrying out this work, it is necessary to achieve the most even surface possible. Despite the fact that the process of pouring the solution is not difficult, it requires accuracy. With a layer thickness of 2 cm, the consumption of the mixture will be 50 kg per 1 m2.
The beacons can only be removed after the mixture has set. This usually happens in at least a day. The voids formed after their removal are filled with a solution. An hour later, the surface of the screed is poured with cement water and rubbed over with a plaster float. If necessary, small irregularities can be rubbed with the addition of a cement-sand mortar.
Important! It will be possible to walk on the screed only after 2 days. You can start laying the floor covering after 14 days. Complete drying of such floors occurs within 25-30 days, depending on the thickness, as well as the temperature and humidity of the room. Thus, concreting the floor with expanded clay allows you to get an economical and high-quality coating in 1.5 months.
Widely used in domestic buildings, as well as in multi-storey construction, expanded clay concrete has gained its popularity due to a number of advantages. Many of the advantages of the material are acquired due to the properties of clay, which is part of expanded clay. This includes low specific gravity, resistance to biological influences, fire resistance, durability, high-quality hydro and thermal insulation. Hence the expanded clay concrete floor screed will provide a secure base for any floor covering.
But there are some negative aspects that complicate its independent use. For example, the period of time of work is far from fast, since concrete requires additional grinding to create an even surface. There are several types of expanded clay screed. It can be a classic fill, semi-dry or dry version. Each type is selected specifically for the building object, the required load on the base, the amount of unevenness in the floor.
Recommended for rooms with irregularities, for floor insulation on the first floors of buildings. Equally well suited for indoor and outdoor work, for giving the floor the necessary slope, when installing a system of underfloor heating. On sale there are options for ready-made building mixtures based on expanded clay. Their use is advisable with high floor differences, up to 30 cm. But even such a solution can be made on our own.
Screed proportions
The required composition is selected depending on the nature of the surface. The ratio of materials depends on the fraction of the expanded clay screed used and the expected loads on the base. In the classical version of pouring, the so-called wet method, the following proportion of cement, water, sand, expanded clay is used - 1: 1: 3: 2. In terms of mass, with a consumption of expanded clay of 0.5-0.7 m3, 1.3-1.5 tons of a mixture of sand and cement will be required.
Variations in the proportion of components allow the preparation of various grades of expanded clay concrete. Thus, for M150, the ratio of cement-sand-expanded clay is 1: 3.5: 5.7. Accordingly, the recipe for a mixture with the same components for the M300 looks like this: 1: 1.9: 3.7. And for a similar grade of concrete M400 - 1: 1.2: 2.7.
It is not at all difficult to make expanded clay concrete with your own hands. First of all, you need to choose the right expanded clay. It is a thermally processed low-melting clay. The material is available in several types:
- expanded clay gravel - elements of a regular round shape;
- expanded clay crushed stone - unformed fractions of large sizes;
- expanded clay sand is a finely crushed result of expanded clay processing.
For the preparation of expanded clay concrete for the floor, only gravel with a fraction of 5-20 is used. Larger ones are used in a semi-dry or dry method. Expanded clay sand makes thin types of screeds less than 3 cm thick more durable and heat-intensive. According to the recommendations, expanded clay should be soaked in water in advance so that the particles do not float. Due to the hydrophilic properties of the material, its porous structure will quickly absorb a sufficient amount of water. The result is a mass of gravel with no visible moisture build-up.
Next, the ratio of sand and cement is added in portions with constant stirring. This continues until the expanded clay granules become cement-colored. The entire screed preparation process is easiest to carry out with a concrete mixer. In the absence of the latter, any spacious metal container capable of containing the entire volume of expanded clay concrete is quite suitable.
It is worth paying special attention to the choice of the brand of cement for concrete. For reliable adhesion and high specific strength, it must be at least M400-M500. Quarry sand for the preparation of expanded clay concrete is washed. It is pre-sieved on its own. To achieve higher strength, frost resistance and durability of the screed, many specialists recommend the addition of plasticizers. The proportions of the additive are determined by the manufacturer of a particular composition and are indicated on the packaging. In addition to the ready-made purchased solution, the plasticizer can be made by yourself using liquid soap or washing powder.
Water is added to the ratio of the solution for the screed at the rate of 200-300 liters per 1 m3. The proportion varies depending on the moisture content of the materials. The main thing here is to achieve the desired consistency so that the mixture is confidently straightened out by the rule. In the case of an excessive amount of moisture, a rare composition will be obtained in which expanded clay will float and also prevent the formation of a flat surface.
Laying the mixture on your own
The consumption of expanded clay concrete depends on the required layer thickness and the size of the floor area to be coated. The minimum thickness of expanded clay concrete screed is 3 cm, which is one of its significant disadvantages, especially in the presence of a low ceiling height.
Before using the mixture, it is recommended to install a waterproofing material and a damper tape. This is necessary to prevent premature loss of moisture in the base, otherwise the monolith will not have time to gain strength. The tape, in turn, serves as a protector against contact with the wall and prevents possible thermal deformation.
The solution is poured at the level between the beacons from the corner of the room. Large irregularities are straightened by the rule. Due to the rapid setting of the composition, the process must be carried out continuously and in a short period of time. It is worth noting the significantly shorter setting time of the expanded clay concrete screed compared to concrete. After two days, you can walk on the hardened screed.
The surface of expanded clay concrete is far from mirrored, therefore it is recommended to sand the base a little before finishing. Further, for the final result, a layer of classic cement-sand screed is poured.
Some experts use a simpler and less time-consuming method of leveling the floor using expanded clay. There is no need to prepare a solution. The dry fraction of expanded clay gravel or crushed stone is poured directly between the lighthouses on a prepared base, leveled. Then you can immediately start pouring the concrete leveling layer. Sometimes expanded clay is additionally spilled with cement milk.
The floor screed is a rough surface that allows you to hide protruding structural elements, floor unevenness, as well as various communication networks. It also works as sound, heat and condensation insulation. The most popular type is expanded clay concrete. It is distinguished by its special efficiency and some features, thanks to which it is widely known.
Expanded clay concrete is made on the basis of high strength granules. They allow you to create a honeycomb structure, which in turn:
- Increases the level of thermal insulation in the floor.
- Protects against external and impact noise.
- Evens out differences in the base of more than 10 cm without significantly increasing the load on the supporting structures of the house (however, a thick layer is difficult to compact).
- Hide the laid engineering networks, as well as the underfloor heating system. Moreover, the latter works most effectively in expanded clay concrete screed. This is due to the fact that it completely excludes possible heat loss.
- Provides a durable layer regardless of room configuration.
Due to its low weight, the screed is practical in houses with a wooden base or old weakened ceiling. The load from it is much lower than with the device of a classic wet cement-sand mixture. It is durable as it effectively resists wear and tear under heavy loads.
In case of temperature changes, it provides excellent frost resistance up to 50 cycles without loss of bearing capacity and cracking. It is worth noting its excellent resistance to fungal microorganisms, rot, mold, and chemical reagents. In direct contact with fire, it does not support combustion and is non-flammable. Such a floor can be made absolutely for any finishing material.
There are also disadvantages:
1. It becomes necessary to grind the surface or apply a finishing layer, since after pouring the solution, expanded clay granules float up, creating a kind of roughness.
2. A significant thickness is required (more than 6-7 mm), which affects the volume of the room. Therefore, for houses with a low ceiling, a DSP with a thickness of 2-3 mm will be preferable.
3. Requires significant labor costs for the device of a large layer.
Manufacturing proportions
To find out the scale of the work, it is necessary to know not only the area of the room, but also the thickness of the poured layer. The resulting volume will show how much clay component is required, from which one should build on further. To obtain various material densities of 1000-1700 kg / m3 (for flooring, it is recommended to choose the highest indicator to ensure good performance), components are used in a certain ratio.
| Density, kg / m3 | Weight per 1 m3 of solution, kg | ||
| Sand | Cement М400 | Expanded clay М700 | |
| 1500 | 430 | 440 | 560 |
| 1600 | 640 | 405 | 505 |
| 1700 | 820 | 390 | 440 |
To moisten the expanded clay well with the above proportions for the screed, add 150-200 liters of clean water per 1 m3. If this volume is not enough and the solution is not wet enough, then the amount can be increased to 250-300 liters. Builders prefer to focus on the simplified material ratios for the M100. This option is no less effective:
- 1 part cement;
- 3 hours of sand;
- 4 hours of medium fraction granules;
- 1 h of water.
Such proportions resemble sand cement, so for simplicity, you can buy a dry mix and add the missing components. If a very strong and durable screed is required, then the ratio changes slightly.
| Expanded clay concrete grade | Sand | Cement | Expanded clay |
| M150 | 3,5 | 1 | 5,6 |
| M200 | 2,5 | 4,8 | |
| M300 | 1,8 | 3,6 | |
| M400 | 1,2 | 2,7 |
Working with M500 Portland cement, when laying the screed in rooms with low operational loads, it is recommended to adhere to the following proportions:
- Cement - 295 kg.
- Coarse sand - 1180 kg.
- Granules - 1300 kg.
- Water - 205 liters.
Lightweight expanded clay screeds with a density of up to 300 kg / m3 are made without adding sand. In this case, it is sufficient to use cement (260-370 kg), aggregate (710-1100 kg) and water (100-230 kg).
The first step is to find a suitable coarse filler. Expanded clay is a low-melting clay that is thermally processed. There are several varieties:
- gravel - particles are extremely round or oval;
- crushed stone - coarse grains with indistinct edges;
- sand - secondary material of fine fraction, obtained in the process of processing expanded clay.
In the manufacture of the screed, gravel of no more than 20 mm is used. Coarse crushed stone up to 40 mm is more practical for semi-dry or dry type. Sand is used for the device of a layer up to 3 mm, as it provides high strength and heat capacity due to the sufficient density of the solution. Before adding the granules, they are soaked in water to prevent the particles from floating. Hydrophilic properties allow moisture to be quickly absorbed, resulting in an increased backfill weight.
First, sand and cement are introduced into the prepared aggregate with regular mixing until the expanded clay acquires a uniform cement shade. It is most effective to use a concrete mixer for such purposes, since this process is quite laborious manually. But if you have to interfere with a shovel, then the batch is recommended to be done in full.
You should pay special attention to the choice of the brand of cement. To make the screed strong and resistant to external influences, you need a brand higher than M400. When applying quarry sand, it is imperative to rinse it from impurities and sift it from debris. By adding special plasticizers, it is possible to provide high heat-insulating and frost-resistant properties. Their introduction is carried out according to the manufacturer's recommendations, but they are replaced with washing powder or liquid soap.
Pure water is added to the solution in an amount of up to 300 liters per 1 m3, although it varies due to the different moisture content of the components. The main goal is to achieve a suitable consistency so that the mixture is easily smoothed by the building rule and is not too thick. However, high humidity will cause the granules to float, which will significantly affect the smoothness of the resulting screed.
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For insulation of floors, especially on the first floors (above the basement) or in situations where the floor is generally located almost on the ground, a claydite-concrete screed is often made with your own hands for thermal insulation. However, there are other, more powerful insulation materials, for example, the same extruded polystyrene foam, but its cost, in comparison with expanded clay, is too high, therefore, most often they resort to the budgetary and, moreover, very convenient option.
Below we will talk with you about how this is applied in practice, and as a supplement, watch the video in this article on the same topic.
How it's done
What is expanded clay
- Expanded clay is obtained by firing clay or shale, resulting in a light porous building material, which can be in the form of crushed stone, but most often, these are oval granules, which can have from 350 kg / m 3 to 600 kg / m 3. Expanded clay sand with a fraction of up to 5 mm has the highest bulk density - up to 600 kg / m 3, a fraction from 5 mm to 10 mm - 450 kg / m 3, from 10 mm to 20 mm - 400 kg / m 3 and from 20 mm to 40 mm - 350kg / m 3.
- It should be noted that this material, with a very high density, has excellent thermal insulation and sound-absorbing qualities, has excellent frost resistance, is fireproof, and its price is the lowest among all possible heat insulators for a floor. In this situation, it can be used both as a bedding and as a filler for expanded clay concrete.
Note. It should be noted that expanded clay very quickly absorbs water, but gives it away for a long time, therefore the instruction recommends storing it in a dry, covered place where water does not flow. The moisture content of the material will further affect the amount of water added to the solution.
Screed
In order to fill a layer of concrete screed with expanded clay, we need an even base, and if this is a reinforced concrete floor, then we can say that the preparation has already been carried out before us, but most often such fillings are done on the ground.
That is why, before tackling the floor screed, we will have to lay out the base - there is no need for a mirror surface at all, but just a flat area on which sand and crushed stone can be poured. But after planning, the soil must be tamped without fail, and if there are depressions, then fill them up so that the pillow lays down evenly.
Now about the pillow - in this case you need sand with crushed stone or the same expanded clay, but if we are talking about light, then, of course, it will be more logical if expanded clay is also used as a bedding, and not crushed stone or gravel.
Now about the shut-off waterproofing - some recommend laying it on top of the pillow, but judge for yourself, the wet bedding conducts the cold very well, so it is better to cut off the bedding itself from the ground, and not just the screed.
- Therefore, we will get such a cake - on the ground (if it is stony, then it needs to be leveled with sand so as not to damage the waterproofing) a film is laid (vapor-permeable or just dense cellophane, roofing material in two layers).
- Then a layer of sand at least 20-30 mm thick, and then a layer of expanded clay (crushed stone), which should also not be less than 30-50 mm. The last layer can be poured at least a meter high - with this level you have to level the rough base, on which, in fact, the concrete screed with expanded clay of a certain fraction will be poured.
- Lighthouses are mounted right on top of the backfill, but sometimes, to give the solution more strength, a plaster mesh is laid on the floor, as in the top photo, or a crate is simply made from pieces of reinforcement, wire, and sometimes even from wooden slats.
Of course, the minimum layer thickness will also depend on the size of the fraction, but for the smallest (5-10 mm) or even for sand, it is not recommended to make the fill thickness less than 30 mm, but this, as an extreme option - it is better to adhere to a minimum of 40-50 mm ...
Before proceeding with the preparation of the solution, it is necessary to determine the proportions of the expanded clay concrete screed, but it is difficult to say exact numbers here - it all depends on the forthcoming load and on the size of the fraction ().
But, nevertheless, it is necessary to decide somehow, therefore, here you can be guided by the generally accepted ratios for residential buildings - 1/3/4, that is, 3 parts of sand and 4 parts of expanded clay will go to one part of M400 cement.
Also, the proportions of the expanded clay concrete screed can be determined by other ratios - for 30 kg of the finished solution (1 cement / 3 M400 cement) add 25 kg of medium fraction expanded clay. It is important to achieve a normal consistency of the solution, since a thick mixture is poorly smoothed by the rule, and in a rare mixture, expanded clay floats up and it is almost impossible to make a mirror.
It is impossible to say here how much water you need for the best consistency, as it will depend on the moisture content of the sand and expanded clay.
If you have everything in order with the consistency, then when you pull the solution along the lighthouses as a rule, then you will get an almost mirror-like surface and pieces of expanded clay will practically not be noticeable (
