Nuts and Bolts of AAC Blocks Manufacturing

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Chemical Composition of AAC

Chemical Components in AAC Blocks If we test AAC Blocks with Spectro Photometer, chemical composition can be found out. One of the same report is given below.

What is AAC? What are the properties of AAC? How AAC blocks are produced?

Definition of AAC Blocks AAC Blocks A - Autoclaved A - Aerated C - Concrete Autoclaved aerated concrete is a lightweight concrete containing uniformly distributed voids that is subjected to high-pressure steam curing. Production of AAC Blocks This is a light- weight building material produced by autoclaving a set mix of fine siliceous materials such as ground silica sand or flyash and the binders like Portland cement and lime. Lightness is achieved by incorporating a large proportion of closed microscopic pores in the slurry with the help of entraining or foaming agent. The basic raw materials are fine-ground sand or fly ash, cement, quicklime, anhydrite or gypsum, water, and aluminum powder or paste as a rising component. A suitable mixture of these raw materials is poured into a mould, and the rising process starts due to the development of hydrogen gas formed by the reaction of aluminium in the alkaline suspension. After 20 to 40 minutes the maximum rising

What is Aluminium Powder? Why it is used in AAC Plants?

Aluminium Metal powder or paste Aluminium powder, which is commonly used as a reaction agent in AAC Plants, is a fine granular powder made up of Aluminium Metal. Process of Manufacture: The aluminium powder is usually manufactured in many forms such as flaky particles, granulated powder (atomised aluminium) etc. There are different processes one can use for the production of aluminium powder. The metal is melted in furnaces, and the temperature is maintained around 720 to 760 C. Atomised Aluminium is produced by blasting the stream of molten Aluminium into small articles by air jet. For this purpose, an atomiser is employed which consists of a straight tube with lower end dipped in molten metal and upper end terminating as a little orifice. A jet of hot air under pressure is passed through armular opening near the top which impinges on a stream of molten Aluminium drawn by suction through the orifice. This results in the formation of small particles of Aluminium. Th

Why the vacuum should be done for AAC Blocks?

Purpose of Evacuation: Before steam is often entered into the autoclave, the autoclave must be evacuated by reducing the pressure within the autoclave with the utilization of vacuum from the air pump or steam ejector. Hereby the existent atmosphere within the autoclave is removed. By keeping the evacuation pressure below the saturation pressure of water, which is out there within the green cakes, steam is released from the green cakes as a desired side effect. Air and hydrogen which are still present within the green cakes are scavenged from the autoclave by this self-formed saturated steam. Why the vacuum should be done for AAC Blocks? The vacuum is mandatory. This will remove the entrapped air from autoclaves. Otherwise, liquid steam marks are going to be visible after autoclaving. Those blocks are sensitive and have a tendency to break easily. If it's not broken, please keep the separate stacking/drying for a couple of days. If there's no vacuum, do the purgi

AAC vs Non AAC Blocks

Why Autoclaving is required when Non Autoclaved Aerated Concrete Blocks are available in the Market? The matrix and the firmness of the AAC products are made due to autoclaving. AAC vs Non AAC Blocks Technically, such product will start cracking by itself when it approaches equilibrium moisture content after a couple of years. In the case of ordinary concrete products, there are no shrinkage troubles during the drying operation. But in foamed or aerated concrete the mixture is air and if manufactured without autoclaving, drying shrinkage will cause cracking. The calcium silicate hydrates formed during autoclaving is more stable than the one formed of cement at room temperature. Autoclaved products have low shrinkage. Cement will need four weeks to achieve its final strength at room temperature whereas, autoclaving takes only 12 hours. to get desired strength. The mechanical strength will not be very high and through the drying, the shrinkage is going to be excessive. It i

Reactions during Autoclaving of AAC Blocks

Reactions during Autoclaving of AAC Blocks In the first phase, a topochemical reaction takes place during which the lime and silica acid are the reactants. Water doesn't happen within the actual rejection; it’s only built into the new formulations that are formed. These reactions occur within the border areas of the raw materials, starting at the active spots (e.g. on the edges) of a crystal. The second phase of the reaction will mainly involve the solvent phase where the lime and silica acid, both of them are dissolved in water, will react into insoluble calcium silicate hydrates. These hydrates will form a structure. Looking at this in a little more detail from when the green blocks enter the autoclave, the main reactions that occur are broadly as follows: Over 2 hours or so, as the pressure and temperature increase, the normal cement hydration products that formed in the green state progressively disappears and the pulverized fly ash becomes reactive. C-S-H(I) forms, partl

AUTOCLAVING - NUTS AND BOLTS OF AAC BLOCKS MANUFACTURING (By Srinivas Goud Chikati)

One and only Book available in the world on this subject - ‘Autoclaving of AAC Blocks'

7 ReasonsWhy this Book Must Be Read 1. India is full of fake AAC consultants. This book will save lakhs of money spending on them. 2. By understanding the process and following the checklists and log sheets, one can save lots of money. 3. This book is written by one of the five senior AAC professionals available in the country with more than 17 years of hands-on experience in AAC Plants. 4. When you are planning the New AAC Plant, this will enable you to choose the right Autoclaves, and the systems connected to it. 5. Most of the plans have no long vision. They hand over the plant to some contractors and ask for the production. They damage everything in 4 or 5 years. This is ok when you want to do business for 4 or 5 years. This book and my next book on Process Control will enable you to choose your own team and manage the plant for a long time. 6. Much attention was given to Safety. If the plant is safe, employees can work without any fear , and productivity will be increase

Non Autoclaved Aerated Concrete Blocks - Can we use them?

The matrix and the firmness of the AAC products are made due to autoclaving. It is possible to form foamed or aerated concrete without autoclaving but the properties are going to be very bad. Of course, such products will contain mostly cement. The mechanical strength will not be very high and through the drying, the shrinkage is going to be excessive. Technically, such a product will start cracking by itself when it approaches equilibrium moisture content after a couple of years. In the case of ordinary concrete products, there are no shrinkage troubles during the drying operation. But in foamed or aerated concrete the mixture is air and if manufactured without autoclaving, drying shrinkage will cause cracking. The calcium silicate hydrates formed during autoclaving is more stable than the one formed of cement at room temperature. Autoclaved products have low shrinkage. Cement will need four weeks to achieve its final strength at room temperature whereas, autoclaving t