Advanced Concrete Technology: Aerated and Foamed concrete

Starting any aerated and foamed concrete production, one has to take into consideration the demand for foamed concrete and aerated concrete, cost of equipment and technological complexity plus raw materials. This is according to Elizabeth of Inntechgroup a modern Russian enterprise that designs and manufactures the equipment for non-autoclaved aerated concrete.

Demand for foamed concrete and aerated concrete

Both materials have high flowability, low self-weight, minimum consumption of aggregate, controlled low strength, and excellent thermal insulation properties. So there is no any significant difference for customer between aerated and foamed concrete blocks.

Cost of equipment

Let us take a closer look at the equipment which is used for production of foamed and aerated concrete blocks.

• Mixer

Mixer designed for foamed concrete production is technically more complicated. Mixing process is going under the pressure by means of foam generators or in the open mixer by means of gerotor type pump. It is vital to maintain the same pressure level but that leads to excessive wear of fillers, gland seal etc. The gerotor type pump is more expensive and technically complicated. On the bright side is slow speed of mixing process and lesser load for bearing unit, you also are able to pour the mixture into the moulds by hoses from distance.
Mixers designed for aerated concrete have simpler construction and easier to use as they mix liquid mixture. All that you need is just to provide mixer with small vanes and high speed for proper mixing process. There is no pressure and special drain devices – mixture is discharged by gravity. There is disadvantage though – you have to arrange movement of moulds or mixer as there is no way to pour the mixture into the moulds from distance

• Molds

The main requirements for molds are size accuracy, quality locks, which prevent leaks, and smooth surface. The moulds are made of thin walled sheet metal with frame made of shaped tubes. These moulds are light, easy to use, move and its production doesn’t require a lot of investments.

Battery molds are popular among foamed concrete producers. These molds are constructed by workers before pouring process and that takes a lot of time. Strict requirements are applied for materials used for production of these molds as they directly influence geometry of blocks and the speed of its construction. That is why molds are made of thick – walled metal which makes it heavier and more expensive. More over at first these molds promote excellent geometry of blocks but later deformations are unpreventable.

• Dosing system

There are various kinds of dosing systems for aerated concrete as well as for foamed concrete. They have similar characteristics so there is no significant difference.

• Cutting device

Using battery molds for foamed concrete you won’t need to cut the array. But some producers use cutting technology for foamed concrete as well as for aerated concrete.
Foamed concrete need more time to develop enough strength before unmolding, it takes from 8 to 20 hours depending on usage of heating devices. As for aerated concrete – it can be cut just in 1,5 – 3 hours after pouring. There is another difference in cutting technology: aerated concrete is cut buy string saws manually or by automated cutting machine. To cut foamed concrete one need to use circular or belt saws. Surely string cutting device costs less than set of saws, besides saws have accelerated wear.

Also Read: Utilizing FRPs for concrete strengthening

Technological complexity and cost of raw materials

Surely the main difference between foamed concrete and aerated concrete is production technology. Foamed concrete is produced by mixing sand, cement, water and foaming agent. Foam is supplied by foaming machine directly into mixer with targeted frequency and weight. During the mixing process particles of cement and sand envelop foam bubbles. The mixture is poured into assembled and lubricated mold. The array gain stripping strength during 12-24 hours.

The main technological difficulties. Maintaining of the same quality of foam requires your continued attention. Unstable foam causes unstable density of product. But the main difficulty is slow development of strength. Production of foamed concrete requires usage of cold water as hot water destructs foam. But cold water doesn’t promote development of strength moreover foaming agent itself slows down cement setting. So that development of stripping strength will take 24 hours, further development of strength is also going on very slow. These factors directly influence consumption of cement.

Aerated concrete. The main components for aerated concrete production are also sand, cement, water. These components are mixed and last minute blowing agent – aluminum powder is added. The mixture is poured into mold and reaction starts. Air bubbles are created as a result of chemical reaction and they blow up the aerated concrete mixture. In 20-30 minutes reaction stops and the array starts to develop stripping strength. Hot water is used for production, its temperature is about 40-60 C. Heat is also generated during reaction so that the temperature of the array is about 50-60 C. That enables rapid development of strength. In 2-3 hours the array should be cut per blocks.

The main technological difficulties. The main difficulty is development of proper technological procedure and composition depending on your raw materials. There is no any unique composition for aerated concrete. The factors which influence the process are water, its quantity, alkalinity, quantity of Aluminium powder. As a rule suppliers of equipment provide full training services and technological regulations for each client individually.
Summary.

There is no difference for your customers whether it is foamed block or aerated concrete block, they will compare quality and price. As the quality is the same they will pick the cheaper one.

Producers should keep in mind that equipment for foamed concrete is technically more complicated, battery molds are more expensive and because of slow circulation you will need bigger quantities. The aerated concrete production equipment will cost less because of less consumption of metal. Moreover aerated concrete equipment is cross functional – you can produce blocks of any sizes! You also will need less quantities of cement (20% of savings) so that prime cost of aerated concrete blocks is much more less that is why the product is more competitive! And competitiveness of the product is half the battle for any producer of construction material.