Foam concrete as a material for construction provides good thermal insulation properties to residential buildings and structures of economic importance. The presence of many small air chambers isolated from each other makes the walls of this material light. Such premises have good sound insulation and high fire safety. In order for the mixture of sand and cement to acquire such properties, it is necessary to add a foaming agent for foam concrete into it.
The solution is obtained by air, the amount of the mixture increases without mass gain. Up to 80% of its total volume can fall to the share of air.
Foam concrete: composition
The main components are: Portland cement M400 or M500, sand, water and a foaming agent for foam concrete. In some cases, expanded clay may be added as a lightweight aggregate. The concrete mixture can have a different density depending on the ratio of components (cement / sand: 1 / 1-1 / 3), it can range from 600 to 1600 kg / m³. For lighter foam concrete, sand is not used.
Drinking water is used, and sand without impurities. To obtain a material of a given density, the water-cement ratio of the solution should be at least 0.38. Decreasing this value will cause the cement to take part of the water from the foam for the reaction.
The quantity of air bubbles depends on the quality of the foaming agent and compliance with the technology of its application. This affects the density and strength of the finished material. Properly prepared white foam is easily held in a bucket if turned upside down.
Technology
To be sure of the quality of foam concrete, attention should be paid to the even distribution of cement in the mixture. To achieve this, it is best to mix it with dry sand until a uniform color and only then dilute it with water.
Recently, in addition to the classical scheme, when foam is added to the ready-mixed concrete solution and mixed at low speeds, porous and barotechnology have been used. Their difference lies in the methods of involving air in the process of formation of the finished mixture.
Porization - the use of a small speed mixer. Foaming agent for foam concrete is added during the mixing process. Air is drawn into the mixture due to the forces of turbulence. Barotechnology - the use of a sealed chamber and pressure during short-term mixing of components. You can add a foaming agent to the water or already finished foam in the required volume.
Frothers: application features
In the 19th century, builders mixed bovine blood into the solution to create a cellular structure of concrete. At the beginning of the 20th century, soap root was used for these purposes . Now you can buy a ready-made foaming agent for foam concrete. Its price will depend on the manufacturer, the country of manufacture and the type of active component. Domestic concentrate can be bought from 70 (Neoplast-5) to 100 rubles per kilogram (PB-Lux). Foreign protein formulations will cost an average of 1.5 times more expensive. For example, GreenFroth in a package of 230 kg (metal barrel) costs 125 rubles, and the cost of a canister (10 liters) is 185 rubles per kilogram.
Such formulations are usually available as ready-to-use commercial products. According to the recipe, they only need to be diluted with water. Next, the solution is fed into a foam generator, where it passes through a special filler. Under the influence of a stream of air supplied under pressure, a stable foam is formed, consisting of a large number of small bubbles.
Another use of the foaming agent is to add the concentrate directly to the water when mixing at high speeds. Turbulence creates foam. Then cement and sand are added to this mixture with constant stirring. The quality of such foam concrete is slightly lower than that prepared according to the classical scheme.
Synthetic and protein foaming agent for foam concrete
The technological scheme uses organic and synthetic components. Protein or protein foaming agents are made by hydrolysis from raw materials of animal origin based on blood. Also used for these purposes is vegetable wood resin after saponification.
Natural foaming agent for foam concrete is considered the most acceptable option in the manufacture of the material used in the construction of residential buildings. This is primarily environmental and sanitary standards. The other side of the issue is the “neutrality” of the reaction of finished products.
Synthetic blowing agents are cheaper. The disadvantage of their use is the inability to produce foam concrete with a low density (less than 300 kg / m³). In addition, the strength of the finished wall blocks is inferior to analogues made on the basis of protein foam.
DIY foaming agent for foam concrete
Ready-made concentrate for the manufacture of aerated concrete is usually sold in large quantities. It is not always possible to purchase it in the required quantity. For private construction, you can prepare a foaming agent for foam concrete at home. To do this, you need pine rosin, carpentry bone glue, caustic soda (caustic soda).
Glue-rosin concentrate makes it possible to obtain up to 500 l of foam from 1 kg. The porosity of the material is uniform. The weight of the foam is about 90 g / l. Subject to technology, the bubbles are small - from 0.1 to 0.4 mm. The concentrate is prepared in about 2 hours. It can be stored for 2-4 weeks. Operating temperature is from 5 to 30 ° C.
Cooking technology
The work is carried out in two stages. First, the base is prepared - rosin soap. For foam concentrate for the preparation of 1 m³ of cellular concrete, you will need: caustic soda (caustic soda) - 0.016 kg, and gum rosin - 0.06 kg. Then, carpentry bone glue - 0.063 kg is introduced into the composition to increase viscosity and resistance.
Soda is diluted with water to a solution density of 1.2 kg / dm³. This mixture is boiled and rosin is gradually crushed (not more than 5 mm). For 1 liter of soda solution, 1.5 kg of rosin will be required. In a boiling water bath, the mixture is kept for 1.5 to 2 hours, stirring constantly until the components are completely dissolved.
Joiner glue (tiled) is prepared in advance. It is pre-crushed and poured with water for a day (1:10). By heating the composition to 60 ° C, stirring to achieve complete dissolution of the particles. After the components are ready, the chilled soap solution is poured into the glue in small portions and mixed. The ratio of glue and soap solutions is 6: 1.