During operation, depending on the intended purpose, a number of technical requirements are presented to the floors of buildings and structures. This is strength, evenness, the maximum value of the specific load, the degree of thermal insulation and so on.
General description of expanded clay concrete
An excellent option from the point of view of price, quality and speed of installation of the floor surface is the laying of a concrete screed that provides perfect evenness and high wear resistance. However, this type of floor has a number of disadvantages - this is a high specific gravity per unit area and a low degree of thermal insulation over the entire depth of the surface. Expanded clay screed, which is lightweight concrete, retains the advantages of a conventional concrete screed, but is devoid of its drawbacks.
The method of producing expanded clay for screed is simple and differs from the classic concrete mortar, consisting of cement, sand, water and gravel, only in that claydite is used instead of gravel. It has the form of gravel with a porous structure in the form of an oval of various fractions from 5 to 40 mm; it is produced industrially by burning clay or its derivatives. The variability of expanded clay fractions is determined by the type of construction work being carried out. The smallest one is used for the production of expanded clay concrete screed and the production of blocks, the middle one is used for bulk insulation of floors and ceilings, the largest one is used for thermal insulation of outbuildings and heating mains.
Types and scope of expanded clay concrete
The classification of expanded clay concrete is quite extensive and depends on the requirements for the type of product, granule density, application and solidity. All these signs are standardized by a brand (for example, expanded clay concrete M100), which determines the class of its application and varies from 35 to 100 kg / cm²:
Expanded clay brand | Application area |
M50 | arrangement of supporting structures, construction of partitions indoors |
M75 | the construction of load-bearing structures in the construction of residential and industrial buildings |
M100 | floor screed |
M150 | production of expanded clay concrete blocks |
M200 | expanded clay concrete blocks and floor slabs |
M300 | installation of engineering structures with a large periodic load |
Given the application, the density of expanded clay concrete is an important characteristic, which is determined by the ratio of mass to volume of the material and has limits from 700 to 1400 kg / cm². Often in buildings of the old and not very old buildings for a number of reasons (subsidence, unskilled installation), significant differences occur in the floor level of adjacent rooms, and sometimes even inside the same room. Leveling to a uniform level using a conventional cement-sand screed can seriously increase the load on the supporting elements of the building, which is extremely undesirable, especially if we are talking about multi-story buildings.
Due to the porosity of expanded clay, the density of expanded clay screed is much lower than the density of heavy concrete, which determines the unconditional priority of its use in such a situation. An increase in the percentage of cement in expanded clay increases the strength of the structure, however, there is a significant increase (up to 1.5 times) in the weight of concrete. Accordingly, the maximum possible reduction in the cement component of the material allows to reduce its bulk weight. In this regard, the brand of Portland cement used in its production must be at least 400.
Advantages of using expanded clay concrete
And does not sink in water, and does not burn in fire. Low thermal conductivity determines the high heat resistance of expanded clay concrete, which means long-term resistance of the material to high temperatures. Even at temperatures above 1000 ° C, expanded clay concrete retains its mechanical properties. Very well, the material shows itself when exposed to moisture. Unlike stones, which, when saturated with water during frost, are destroyed, expanded clay concrete has high frost resistance, that is, the ability to repeatedly freeze and thaw without loss of strength.
Another important factor determining the priority choice of expanded clay as a filler for concrete is its environmental friendliness. It does not emit harmful substances either under the influence of an aggressive environment, or over time, or with complete destruction. This explains its choice as a building material and insulation in residential premises.
Preparation of the base for filling the floor with expanded clay concrete
If the screed is made over an existing even and dense coating, then this stage of the work can be skipped. However, most often, pouring is performed directly on the ground, in this case, additional preparation of the base is required. The surface is leveled and carefully compacted, the pits are covered with sand, the protrusions are knocked down to evenly lay the pillow. The pillow is a layer of sand about 2-3 cm and a layer of expanded clay or gravel 3-5 cm thick, possibly more, up to the level of the rough base. Next, a plastic film or roofing material is laid for waterproofing the future screed, a masonry net is mounted and beacons are installed.
Types and methods of using expanded clay screeds
Having figured out the basic properties and technical characteristics of expanded clay concrete, its pros and cons, we will try to understand how to properly fill the floor using this material. The choice of the type of expanded clay concrete screed depends on the type of base on which it is made, in connection with which the floor screed can be of three types. Let's consider each of them.
Dry screed
Expanded clay gravel is evenly and without cement-sand mixture distributed over a prepared, cleaned and compacted surface of the base, not reaching 2 cm to the lower level of the lighthouse. The thickness of the floor screed in this case is determined by the required degree of thermal insulation. Next, the entire area is spilled with cement milk, which is made by mixing cement with a large amount of water without adding sand. This procedure will fix the expanded clay and cover the gravel with a thin protective layer that prevents moisture from being drawn from the finish screed, which will give additional strength to the floor. After that, perform the usual thin screed. The advantages of this method are the installation speed, the cons - low surface strength.
Wet screed
With this option, so much water is added to the solution that the light and porous expanded clay after flooding the screed floats to the surface. Concrete hardening takes a little longer, the entire filler is concentrated at the top of the screed. The pluses include the self-leveling of the mixture. By cons - long drying, the need for special preparation of the coated surface to avoid leaks, as well as the subsequent surface screed, if necessary, to obtain a smooth surface. In this way, attic rooms and outbuildings are usually insulated.
Semi-dry screed
The most common type of expanded clay coating, which by the manufacturing method is identical to ordinary concrete. For the correct filling of the floor in this way, M100 expanded clay concrete is used. In its manufacture, expanded clay of the first fraction with a diameter of 5-10 mm is taken. The proportions of the mixture are as follows: 1 part of Portland cement grade 400 - 3 parts of sand - 4 parts of expanded clay. As for the amount of water, this parameter must be selected individually, depending on the humidity of the sand. It is necessary to achieve a consistency in which the granules of the material would not float to the surface, which makes smoothing difficult, at the same time, the solution should not be too dry, as this complicates its laying and can lead to the formation of voids and cracks in the mass of the screed.
The solution is mixed in a concrete mixer or in a large container. Using a mixer nozzle is extremely problematic due to small portions during one batch, and this makes laying long, the solution turns out to be of different consistency, and expanded clay is distributed unevenly in the concrete mass. The sequence of mixing the ingredients in different sources is described differently, but in practice this does not matter. The main thing is that the solution is uniform and the expanded clay granules are completely coated with a binder.
Screed thickness
The solution is applied evenly over the entire surface to be coated, and the condition must be met - the thickness of the floor screed from expanded clay should be at least 3 cm, usually it is 4-6 cm. If the correct consistency of the solution is chosen, the surface will turn out perfectly smooth and will only have to be made its grouting a day after installation. The advantages of this method of coating are obvious - the ability to use for any kind of floor and floors. The disadvantage is the high complexity, filling using beacons and the need for finishing grout.