Not many people clearly understand the difference between such concepts as “cellular concrete”, “aerated concrete”, “foam concrete”, “gas silicate”, as well as the terms “non-autoclaved” and “autoclaved” concrete that appear along the way. Let’s figure it out with you, what are these – several names of the same material or six different ones? As it turns out, it’s neither.
Of the above concepts, the key and fundamental is “cellular concrete”.
Cellular concrete in its structure is an artificial stone of high porosity, with cells (pores) evenly distributed throughout the structure. This structure gives the material high physical and mechanical properties, making it a very effective wall building material, which is widely used in modern construction.
There are two main technologies for the production of cellular concrete – autoclave and non-autoclave method. With the autoclave method for the production of cellular concrete, the blocks formed from it undergo a special heat treatment in an environment of water vapor in an autoclave furnace at high temperature (up to 200 ° C) and pressure (about 0.8-1.3 MPa). This treatment not only significantly accelerates the process of solidification of the mixture, but also contributes to the mineralization of the material, thereby significantly increasing its strength, reliability and uniformity of the internal structure. With the autoclave method of producing blocks, their shrinkage is reduced several times, which makes it possible to obtain a building material with high dimensional accuracy and correct geometry at the output. With a non-autoclave method for the production of cellular concrete, the hardening process occurs under normal conditions.
In the process of drying, closed cells are formed inside the blocks, which are filled with air. As a result of natural hardening, the blocks are less durable and not as ideal in shape as in the autoclave production method. In addition, the blocks have a large shrinkage. All produced cellular concrete, depending on the technology for the formation of a porous internal structure, is usually divided into two main varieties: foam concrete and aerated concrete.
Foam concrete is obtained as a result of the hardening of the solution, the main components of which are cement, sand, water, and also a foaming agent. Almost any substance that can create foam can act as a foaming agent, even ordinary washing powder. The production of foam concrete does not require sophisticated equipment, it can be produced even by a handicraft method.
Foam concrete, depending on the method of hardening, can be both non-autoclave and autoclave. The greatest popularity in our country, due to the simplicity and cheapness of production, was received by foam concrete made by the non-autoclave method of hardening. The composition of aerated concrete includes quartz sand, cement, quicklime, water and a special blowing agent (usually aluminum powder). A gas generator is added to the prepared mixture, which contributes to the evolution of hydrogen and an increase in the volume of the mixture by several times. After that, the concrete mass is subjected to heat treatment in autoclave ovens and cut into blocks.
Aerated concrete is produced exclusively in industrial conditions. Gas silicate and aerated concrete, in fact, are two synonymous terms for the same material, which is made of cellular concrete with a porous structure obtained as a result of the reaction of a prepared concrete mixture with an aluminum suspension. Depending on the percentage of lime and cement that make up the concrete, it is conditionally customary to distinguish between gas silicate and aerated concrete.
So blocks, in which there is a greater quantitative content of cement, are called aerated concrete (they are more durable), and those in which there is more lime – gas silicate (they are warmer). This division is purely conditional, not having a clear definition in the special construction literature.
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