Master the Art and Science of AAC Technology

Mastering AAC Blocks

AAC blocks are here to stay, and AAC technology is the future of the construction industry. This book will gently hold your hand and help you gain mastery of this technology in an effortless conversational style.

What you will get in this book?

What is the step-by-step procedure for using the AAC blocks on site? What are the tricks and tips for using AAC Blocks for superior masonry construction?

How do many prominent labs make mistakes while testing AAC blocks, and how to test AAC Blocks correctly?

How are AAC blocks manufactured, and why do we call them “Dhokla of Concrete”?

What is the fantastic twin system tobermorite chemistry in AAC technology?

Why do AAC block walls crack, and how do you avoid these cracks?

This book will also give you links to download Work Procedures in various aspects of AAC usage on site.


Chapters we've covered

Do you remember trying to use a touchscreen phone for the first time? We felt like throwing away this horrible touchscreen device and sticking to our comfortable QWERTY keyboard phone. But as we adapted over the years, we realized that the monster was our friend. A shift from red clay bricks to AAC blocks is a similar challenging transition.

1.1 Environmental Protection through the AAC Blocks
1.2 But Why AAC?

AAC chemistry, like a Twenty20 cricket game, has two batsmen. They bat and score runs individually, and give strength to the AAC product. These two batsmen are Cement and Lime. They undergo their own hydration reactions – independent of each other. And they both contribute to the strength of the product.

Let's look at this twin hydration system closely...

In 2013, I was possessed by the idea of setting up an AAC plant. It was the "in-thing". I wanted to become a first-generation entrepreneur – with no business background in the family. You may say that a mid-life bug had bitten me. And I took the plunge. Describing how we sailed through the ups and downs of the business is a long story, but all I can say here is that the journey was worthwhile.

I have a book on setting up and running an AAC block plant, "How To Run Your AAC Block Plant". It will discuss many finer points like finalizing the plant layout, controlling the process parameters, maximising production, and ensuring top product quality. The above book is written for readers who want to either set up a plant or for those facing challenges in running a plant. Both these topics – setting up a plant and running it – contain an ocean of information and merit a separate book.

In this chapter, we will look at the production process of AAC blocks.

"Show me the proof", my client shouted at me. I had no clue what to say. It was one of those hard days when I did not know how to speak to my client. He was furious about the weight of the blocks. The truck had reached the client's site, and his unloading workmen informed him that these blocks were heavier than the last truck they received.

The client immediately took two samples to the laboratory – one from the last truck and one from the current truck. And yes indeed, there was a substantial difference in the weight of both the blocks. The client was on the phone with me, "What kind of consistency do you have in your production?"

After I understood the issue, I explained the concept of dry density and IS code requirements to my client – but he thought I was trying to fool him by using technical terminology Finally, he asked me the above question, "Show me the proof – that what you are saying is the truth."

This chapter is for those who will need proof to show your client.This chapter is also for those who genuinely want to understand how to test AAC blocks.

As much as the taste of a biryani depends on the cook, so do the test results of an AAC block depend on the technician. Not Good. Sorry for the unscientific comparison with Biryani, but one slip from the lab technician and the results are distorted. Therefore, this chapter alerts us to the pitfalls, even though the IS codes give step-by-step procedures for all five parameters.

The IS code 2185 (part 3) has specified five properties for the AAC blocks. We have seen them in detail in the previous chapter. Interestingly, test procedures are not given for these parameters in the IS code 2185 part (3). The following list shows the test parameters and the corresponding IS code numbers specified for its test procedure

We will briefly discuss the test procedures to be followed for these tests. The first one is the dimensional tolerance which can be easily checked with an accurate measuring scale. The rest of the four tests need detailed procedures ...

At the end of World War 1, Europe wanted a building material that would keep the cold from coming inside. This material had to be cheap, readily available and easy to work with. What else would fulfil these three criteria than some form of concrete? The AAC blocks were invented to keep the building thermally insulated – to keep the cold out in Europe and the heat out for us in India.

We measure heat by a simple unit of degree Celsius. But this unit doesn't tell us directly about the property of building material. We need to know the flow of heat through a surface in a building material to check its suitability. The terms U value and R value inform us about this unique property of every building material – the flow of heat through a wall surface. Both these terms are opposite to each other

A high R-value means a low U-value, but their real difference is much more complex.U-value is more of an engineering term as it describes thermal performance. When looking for a building material for your structure, you usually look for a high R-value because you want the heat (or cold) to stop coming inside.

The unit of R-value is m2K/W whereas the unit of U value is precisely the opposite of W/m2K.

Imagine you want to construct a house for the wealthiest person in the world. You want to use quality building materials for the construction. Cost no concern. What will you use for masonry?

A customer has enormous choices today – each material offers some unique perspective to the customer. But how does a customer evaluate the suitability of these products in his construction? Not every customer is going to value environmental protection. Few may want faster speed and lower cost of construction. Others may need safety features like earthquake resistance and fire resistance. And few others will value comfort factors like high thermal insulation and low lifetime cost of the structure.

And what about ease of construction – like that famous TV commercial "Fill it, Shut it and Forget it?" Since you want to construct a house for the richest person in the world, you may need all the above benefits in a single product. You may want the house to have high fire resistance and earthquake resistance; you may want lifetime comfort for its occupants, or you would need high product consistency and possibly a faster speed of construction

Is it even possible to get all this in a single product?

Go and ask any site engineer. What is the one thing he is most worried about the AAC blocks? His answer will always be cracking in the wall. The problem is compounded due to a lot of misinformation on this subject. In this chapter, we will see various causes of masonry wall cracking and how to eliminate these causes at the root level. There are three secrets to superior AAC masonry construction. Once you learn these secrets, you will master AAC wall construction. But first, let us look at the four causes that lead to cracking in AAC block wall:

8.1 Cracking Cause No 1: Drying Shrinkage of AAC blocks
8.2 Cracking Cause No 2: Deflection of beam above the wall

1. The AAC block has cracked at some places in the wall. What is the reason?
2. The Chakravyuha of Compressive Strength Test


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About Book Author

Mukund Joshi

Mukund Joshi did his civil engineering from Mumbai University in 1991 and further became Member of Institute of Concrete Technologists – City and Guilds London. He runs a YouTube channel on AAC blocks. Apart from AAC, his passions are writing and long-distance running. He stays at Nashik, Maharashtra.

  • Mukund Joshi has worked on numerous international projects as a concrete technologist in more than 8 countries over the last 30 years. He specializes in the application of fly ash and GGBFS in concrete.
  • He set up his own AAC block plant in the year 2014 – which is one of the largest plants in India today.
  • He advises various clients in plant operation and application of AAC blocks on sites. year
  • Contact Author at :

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What people said about my work

" Mukund Joshi is a top expert on AAC blocks and is known as the father of AAC blocks in India. We were lucky to have him over for 2 engaging episodes on AAC blocks and the subscribers loved his simple way of explaining a complex product. AAC block is a relatively new product in India, and there is no clear information on this crucial subject. I am sure this book will help site engineers and architects to avoid and even eliminate cracking of blocks on the site.? "

"Mukund Joshi was ahead of the era of green cement which has been presently influencing positively our environment. To help me to create an improved concrete quality he started teaching the construction fraternity how to use fly ash as a partial cement replacement. From this basis he introduced the second recycling stage by successfully using fly ash as a main component in AAC blocks which brings again a multitude of environemental benefits. This book will be a great help to all who want to learn from him."

" I have known the author for over twenty years and can think of few people who possess the deep professional knowledge, technical capabilities, and international exposure required to write such a book as this. "

" The book "Mastering AAC Blocks" by Mukund Joshi is an important guidebook for all field engineers. It explains in detail various work procedures and will be helpful to all AAC users. I know Mukund for more than 20 years now, and he has a knack for explaining complex ideas in simple words. Wishing this book a success. "

" I benefitted from the technical expertise and teaching capabilities of Mukund Joshi in the time when we were colleagues. Already couple of years ago we were aware that recycling the waste into construction materials is one of the biggest challenges faced by mankind today. AAC Blocks can help to resolve this challenge as they contain more than 65 % fly ash. Mastering AAC Blocks is an excellent Guidebook on production, testing and using the blocks on site for everybody who also cares about our environment. "

" The book "Mastering AAC Blocks" by Mukund Joshi is an important guidebook for all field engineers. It explains in detail various work procedures and will be helpful to all AAC users. I know Mukund for more than 20 years now, and he has a knack for explaining complex ideas in simple words. Wishing this book a success. "