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Recipe Calculation for AAC Blocks


Recipe is nothing but knowing the dry weight (batch weight) of one batch or one cake.

To find out dry weight, we should know the desired dry density of final block.
Let us work on the density of 600 kg/m³.

Batch Weight = Density x Mould volume
Density = 600 kg/m3

Dimensions of the mould :
Length = 4840 mm = 4.84 M
Width = 1250 mm = 1.25 M
Height = 670 mm = 0.67 M

Volume of the mould: 4.84 M x 1.25 M x 0.67 M = 4.0535 M³

Batch Weight = 600 x 4.0535 = 2432 kg

(We have taken mould height 670 mm, which is actually depth of the mould. Generally we maintain the cake height equal to mould level. But in some AAC factories, cake height may be 650 mm or 680 mm depending on the parameters like quantity of returns required, sinking of cake, uneven surface of the cake, etc., In this case cake height should be taken to calculate the volume.)

Batch weight or Dry weight consists of binders (Cement and Quicklime), Fly ash or Sand, returns and anhydrite.

Usually the amount of binders is in the range of 25 to 30 %. 

The ratio quicklime/cement often is in the range of 1/2 to 1/2.5.

The ratio anhydrite/solids should be in very low quantities at about 1 or 2% due to scaling or jamming of pipelines.

The ratio of returns/solids is about 20 %.

Recipe:

Lime - 7 to 9 %
Cement - 17 to 20 %
Returns - 15 to 20 %
Anhydrite -  1 to 2 %
Fly ash - 55 to 60 %

Solid/water ratio is about 40%.

The amount of aluminium is in the range of 0.05 to 0.08%, depending on the usage of powder or paste, fineness and quality of the aluminium.

Most of the plants follow the above range and the recipe will differ from plant to plant.


For example, let us take the case of AAC Division of a Large Cement Company.

They have two AAC plants in India. One Plant (North India) is closed and other plant (South India) is struggling at present. When both the plants were running at best during 2013-2016, recipes of the both the plants were different though the machinery of the both the plants were of same size and of same capacity.

So, one cannot copy the recipe of the plant and apply in other plant. Unfortunately, we had great consultants (at least in India) who had no hands-on experience. Those who had the experience of more than twenty years are employed by the best brands in the Industry like Ascolite, Ecolite, Shreeshakthi, etc.

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