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

Technology of production of aerated concrete by conveyor technology
(non-Autoclaved Aerated Concrete 60-100)

Equipment for the production of aerated concrete (non-Autoclaved Aerated Concrete) by conveyor technology suggests the possibility for achieving maximum performance with round-the-clock operation (2 shifts). Interval performance for this type of equipment for aerated concrete ranges from 60 to 100 cubic meters per day, or from 20 to 50 cubic meters per shift. The parameters of the final product - aerated concrete, 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. Conveyor manufacturing method allows to make three-fold turning of shuttering per day, that significantly reduces steel intensity and, as a consequence, the cost of equipment. Process automation for the ingredients feed for aerated concrete production significantly reduces the use of manual labor, resulting in a decrease in the cost of the final product (gazoblocks). The use of inexpensive and reliable cutting device of string type allows to get a proper geometry of the block (+ - 1-2mm) at high speed of cutting.

Input products

(From what non-Autoclaved Aerated Concrete 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 technological production process

(How to produce aerated concrete by conveyor technology)

Conveyor 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);
  • Thermal treatment in warm-up camera.
  • 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);
  • The mold, filled with a mixture of aerated concrete, moves from filling point to cutting point, the rising of the mixture and preliminary getting of the stripping strength occur during removal, at the same time the pouring of the next mold is made.
  • In 90-140 minutes the array comes to the cutting point. At this moment the aerated concrete array has a high flexibility and can be easily processed. Cutting of the crusts and cutting into blocks are carried out by fully automatic cutting device, cutting precision is +/- 2 mm, that corresponds to GOST (all-Union State Standard).
  • The mold with slashed array is removed on tilter to warm-up camera, where the further stripping strength carries on within 5-6 hours at the temperature of 40-50 C . The molds are moved automatically by push mechanism in camera.
  • After 6 hours the mold moves out from the warm-up camera, and 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, that enables to get high productivity and turnover of the molds.

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