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Showing posts from 2020

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

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All the AAC family members are requested to subscribe the site to get latest updates and the notifications of new posts.. All the subscribers will get free E-Book (related to AAC) by mail in pdf format so that you can share the same with your team members. By the end of this year, you will find in the site that nothing is left on AAC. So, please ask questions and we will post the answers with details.  

Cracks in AAC Block Walls

Why there are more complaints of Cracks in Walls made with AAC Blocks : Drying Shrinkage During the manufacturing, when AAC blocks come out after autoclaving, they have high amount of residual moisture from 24 to 28%. (This is the reason most of the manufacturers do not despatch the blocks to the market as the strength of the blocks is less and they tend to chip or crack during loading and unloading of the blocks.) This residual moisture leaves the blocks predominantly in the first 48 hours. As the moisture leaves the blocks they shrink. Imagine we have got installed these blocks during a masonry wall within the primary 48 hours then the shrinkage happens inside the wall. The shrinkage may be a massive force which tears the wall vertically resulting into a crack at the centre of the length of the wall. On the other hand if the blocks are allowed to “dry down” for a period of 48 hours to 96 hours before they go in a masonry wall, then you will find that the cracks in your

Autoclaved Aerated Concrete - Properties, Testing and Design (Kindle Edition) By S. Aroni

 Autoclaved Aerated Concrete - Properties, Testing and Design (Kindle Edition) By S. Aroni    Book Description ‘BIBLE OF AAC’. Every AAC industry in the world and each professional in AAC must have this e-book in hand. This is a comprehensive guide to autoclaved aerated concrete (AAC) for civil engineers, architects, specifiers, industry professionals and manufacturers. It provides the code of practice for the structural use of AAC blocks and panels and provides designers with a complete guide to the structural use of AAC in structural applications in the large homes or buildings. Table of Contents Preface. Introduction. Part 1: Recommended practice Introduction. Production and structure of the material. Properties of the material. Structural design. Structural analysis of elements. Design of unreinforced masonry. Seismic design. Connections and fixtures. Non-structural performance design. Manufacturing control procedure. Execution of works and site contr

ABC of AAC Autoclaving

The primary purpose of the Autoclaving is to transform the green cake into white cake. This transformation takes place in autoclaves, where the green cakes are left for curing. The actual curing takes place by filling the autoclave with pressurised steam (saturated water vapour) supplied by the boiler. It is during this environment where the most reaction will happen between the sand or PFA and therefore the binding agents lime and cement. This reaction, which results in the forming of calcium silicate hydrates within the cellular concrete’s matrix, takes place in two reaction phases. 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 reaction; 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

Quick lime

What is Quick lime or Burnt Lime? Burnt Lime also called as quick lime or calcium oxide is formed out of lime stone deposits or mines which are wide spread throughout India. The calcium oxide is extensively used as a mortar within the construction of building by mixing in with suitable proportion of sand and surkhee of burnt clay as aggregate. It is also used for white washing of homes and building. Foundries, Iron and steel plants use lime as a fluxing agent in their process. Some drugs and pharmaceuticals, paper industry, pesticides formulations and other chemical processing industries are using the unslaked lime or Quick lime. As there are many applications of the quick lime, we should ensure particular properties of the quick lime for using in the recipe of AAC Blocks. Properties required for Quick lime in AAC manufacturing: Process of Manufacture The limestone mined from quarry or rivers should be free from all defects and impurities, once washed and cle