In some cases, instead of the usual classic screed, you need a light screed, for example, to lighten the load on the slab at the expense of the concrete. There are several options for reducing the density of concrete mortar, but they are all based on the addition of materials that lighten the mixture. In this article, we will focus on the preparation of lightweight mortars for pouring the floor, the types and advantages. In addition, we will briefly consider the features of different fillers.
Ways to reduce the weight of the floor
- Application of ready mixes with light fillers;
- Independent addition of components to the mortar, reducing the density.
Prepared mixes consist of cement, one or more fillers, and special additives. Lightweight screeds can be used in the case of a wooden base and on normal concrete. The application of the mixtures is limited to certain conditions. They are not suitable for outdoor areas and for cold rooms (+10 degrees and below). The humidity of the poured floor to create a quality surface must be within 85%. There are no other restrictions on use. Lightweight concrete has several advantages: it quickly sets and dries. In almost a day you can lay the finishing coat. The advantages of the materials include excellent thermal insulation. In addition, there is a good protection against the penetration of extraneous sounds. Lightweight concrete is easy and plastic in the process of pouring. Without much effort it is possible to smooth out all the irregularities. After pouring and drying, shrinkage is only 0.5 mm per meter of thickness. Manufacturers produce powdered materials in large packages. There are instructions on how to dilute the mortar on the package. It must be strictly adhered to and do not allow excessive moisture in the finished concrete.
Fillers for independent preparation of the mixture
By adding fillers, you can achieve a reduction in density without much loss of strength characteristics. In addition, less lightweight concrete is needed for pouring the same area, which saves money on repairs. There are several popular aggregates: expanded clay, vermiculite, perlite.
Represents oval-shaped granules with many pores. Manufacturers produce the material in different fractions (sizes). It is produced on the basis of clay in kilns for firing at a temperature of about 1000 degrees Celsius. The specific gravity is between 250-600 kg/m3. After adding the filler to the cement mortar you get expanded clay concrete. If it is laid in a layer of 1 cm, the weight of the material will not exceed 18 kg/m2.
Material of natural origin, layered in structure. When heated to the desired temperature, it is pulled out of it silvery threads with high strength properties. Such qualities allow to use vermiculite for the preparation of lightweight, but durable concrete. The inflated material is used in construction everywhere. It has a high absorption capacity – 0.1 kg of the filler can absorb up to 0.4 kg of water. This advantage allows for a high degree of homogeneity when added to mortars. As a result of pouring, a very strong base is obtained. The finished floor has a high degree of sound insulation and low thermal conductivity.
In order to use perlite in construction, it has to be heated to a temperature of more than 1000 degrees Celsius. After that, the granules of the mineral material swell up and completely give up the water they contain. The finished perlite is similar in appearance to the usual crushed stone of small fractions. Of the differences we can highlight the low density and good properties of sound and thermal insulation. What fractions are used for pouring the floor? In order to get a really high-quality floor with predetermined properties, it is necessary to choose the right size of aggregate fractions. Large granules have an increased surface area and are not suitable for mixtures. Such concrete has poor strength characteristics. For self-made concrete, it is necessary to adhere to the following pellet sizes:
- Claydite – 5-10 mm. Sometimes used for double screeds and pellets 20 mm;
- Vermiculite – 0.6-2 mm;
- Perlite – no more than 15 mm.
The humidity of ready-made granules before mixing the mortar should not exceed 10%. Otherwise, the filler must be dried.