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INNTECHGROUP - Equipment for the production of aerated concrete (non-Autoclaved Aerated Concrete)

Technology of aerated concrete production by classical technology
(non-Autoclaved Aerated Concrete 25-50)

Equipment for the production of non-autoclaved aerated concrete (non-autoclaved gasobeton) by classical technology suggests the possibility of manufacturing of aerated concrete of excellent quality with minimal initial investment. Interval performance for this type of equipment for non-autoclaved gasobeton ranges from 10 to 50 cubic meters per day, or from 10 to 25 cubic meters per shift. The parameters of the final product non-autoclaved gasobeton, range from D500 B1, 5 to D800 B2, 5. Standard geometric dimensions - length - 600 mm, Height - 300 mm, width - from 100 mm to 400 mm in steps of 100 mm. Classical technology (mobile mixer and immobile forms ) permits to make double turning of shuttering per day, by the following of the temperature regime. Cutting technology and forms of large size facilitates the decrease of steel intensity and price of equipment. Using of inexpensive and reliable cutting installation of manual type allows to get a pretty good geometry of the block.

Input products

(From what non-autoclaved gasobeton is made)

The main components for the production of aerated water are cement, fine aggregate (sand, gypsum, etc.), and blowing agent (aluminium powder)


Water

For making of aerated concrete mixture, city water or water from wells are usually used. In most cases, common drinking water is used. In the case of process water, water from surface sources is preferable, unsalted (salt content not more than 5000 mg / liter), of soft or medium hardness (pH 4 - 12.5), free of oil products, fats and oils. For the process it is necessary to ensure the essential quantity of water heated to a temperature of 40-60 degrees. The demand for water is from 0.5 to 1.5 cubic meters / hour depending on the line's productivity.


Portland cement. (Cement binder)

For the production of non-autoclaved aerated concrete the Portland cement of such brands as M500 D0 - M400D20 is preferred. Aerated concrete manufacture demands for Portland cement concern alkalinity and is determined by the amount of free CaO and Na2O + K2O, which in 1 liter must be at least 75 mg. We do not recommend the use of cements with mineral additives (trass, mold, rotten stone, burnt clay), as well as hydrophobic, sulphate-resistantsulfate and pozzolanic. Cements of different manufacturers differ in their chemical and mineralogical composition, terms of setting, time of curing, so correction of production technology with the use of particular cement is required. As a rule, the required quality of aerated concrete can be obtained at any of the recommended cements, which are available in a particular region.


Fillers and filling matters

Sand is used as the main filling matter. Basic requirements for the sand: a fineness modulus is not more than 1.5 and the minimum content of silt and clay materials.

Various inert and active mineral additives and industrial waste are used as fillers in the composition of aerated concrete: limestone flour, mineral powder, dolomite flour, fly ash from thermal power plants, ash-slag mix, granulated blast-furnace slag.


General requirements:

- Samples of the ash mixture (ash-slag mixture, slag) with Portland cement must provide the equability of volume changing when samples are tested in boiling water;

- Fineness of grinding (content of particles d 0,25 mm is not less than 85%);

- Chemical composition that doesnt hinder the process of gasification.

The use of these fillers requires the correcting of composition of gas concrete mixture, but at the same time, small filler saves cement that significantly affects the cost.


Blowing agent

Aluminum powder PAP-1 or PAP-2 are used as the blowing agent. As a surfactant (surface active agent), causing the reduce of surface tension and better distribution of particles of aluminum powder in the mixture, providing the necessary wettability, the laundry soap, sulfonol (powder or powdered detergent) are used.


Chemical additives

To control the processes of gasification, the rate of curing and other characteristics of the chemical additives are used. Specific set of supplements and their dosage are determined during commissioning, because it significantly depends on the customers feedstock and customer's quality requirements for the final product. The main types of chemical additives: sulphonate - powder, calcium chloride, technical calcined, natural sodium sulfate (purified), Caustic soda.


Description of production process.

(How to produce non-autoclaved gasobeton by classical technology)

Classical technology for non-autoclaved aerated concrete production consists of the following basic operations:

  • Preparation of forms to filling (assembly, lubrication);
  • Preparation and pouring the mixture (dosing, mixing, filling);
  • Cutting of aerated concrete array (crust removal, cut into blocks);
  • Curing of aerated concrete array until getting of the stripping strength;
  • Removing of the finished product from mold to Euro-palettes for packing.


Technological operations' sequence is shown on the Figure 1 and corresponds as follows:

  • Cement handling is carried out by screw conveyor from cement silo to an intermediate dispensing hopper. Dispensing is made automatically by sensors readings of strain gauge platform.
  • Sand is fed by belt conveyor into the sand measuring hopper. Upon reaching of the pregaged values of the mass of sand in the hopper, the conveyor is automatically switched off.
  • Water heated up to 40-50 C, is dosed by flow-metered dispenser (electronic control, precision of 0.1 liters) and poured into the intermediate tank. This tank is equipped with a drainage pipeline of large diameter for easy draining of water into the mixer.
  • Blowing agent is dosed by volume by using of measuring tank. In the mixing tank mixing with the water and a small amount of sulfanol takes place (or other CMS) and activation occurs.
  • Water from the intermediate tank is drained into the mixer. During the drain the mixer must be switched on to form a turbulent funnel.
  • Cement is poured to the mixer made from intermediate tanks, and in one minute the same happens to sand, the mixing of components in the mixer occurs within 2 - 3 minutes.
  • At the end of mixing before draining the mixture chemical additives (accelerators of hardening, plasticizers - if necessary) and then blowing agent are added.
  • Thoroughly mixed solution is drained into prepared mold. Making of the aerated concrete mixture and pouring into molds should be carried out under a positive environment temperature (from +18 C);
  • Along with the final stage of mixing the mixer moves to the form prepared to filling.
  • In the form, filled with a mixture of aerated concrete the rising of the mixture and preliminary getting of the stripping strength occur, at the same time the pouring of the next mold is made.
  • In 90 - 140 minutes an array gets the stripping strength and is available for cutting. At this time an array of aerated concrete has a high flexibility and can be easily processed. Cutting of the crusts occurs before removing the boards, which act as guides for the saw.
  • Aerated concrete array is cut into blocks using the cutting installation of manual type, accuracy of cutting is + / - 3 mm, which corresponds to GOST (all-Union State Standard).
  • A heat insulating cover is put on the mold with slashed array and further getting of the stripping strength is passing for 5 - 8 hours. Using the cover allows you to protect the array from the influence of drafts and heat loss, that permits to produce consistent quality of the block;
  • After 5 - 8 hours fabricated blocks are removed to the Euro-palettes, they are packed and sent to the finished product storage;
  • Disengaged mold is prepared to filling - is cleared and lubricated , the boards are installed.
  • The cycle repeats itself, all actions in the production process occur simultaneously, which enables to get high productivity and turnover of the molds.

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