This document discusses autoclaved aerated concrete (AAC) blocks, an alternative building material invented in 1923 as a more sustainable replacement for clay bricks. AAC blocks are made from fly ash, lime, cement, aluminum, and water, which creates a lightweight cellular structure through an aeration process. Key advantages of AAC blocks over clay bricks include using waste materials like fly ash, requiring less water and labor during construction, providing better insulation, durability, and fire resistance. The document outlines the manufacturing process and types of AAC blocks available before concluding that AAC blocks are recommended over clay bricks due to cost savings and reduced environmental and social impacts.

1. CONSTRUCTION
USING AAC
BLOCKS

2. INTRODUCTION
Autoclaved aerated concrete brick
was invented in mid-1923 in Sweden
by a Swedish architect Dr. Johan
Errikson, who was looking for a
alternate building material having
quality of :-
 Wood – good thermal insulation,
solid structure and easy to work.
Without the disadvantage of
combustibility and decay

3. It is now considered as a new generation brick also known as
Autoclaved Cellular Concrete (ACC) bricks or Autoclaved
Lightweight Concrete (ALC) bricks or, autoclaved aerated concrete
bricks(AAC).
These AAC bricks are made with a mixture of cement, fly ash, lime,
aluminium and water involving an aeration process that gives it
the unique cellular structure.

4. ITS IMPORTANCE IN NEXT GENERATION CONSTRUCTION.
It seems important for the next generation construction because it
involves –
Use of waste Product:-
Fly Ash is usually a by-product of thermal power plants and is an
important raw material in the manufacture of AAC Blocks.
Water Conservation :-
AAC blocks don’t need curing, as water used in other ordinary Clay

5. Durability:- AAC has a very porous structure filled by Air Bubbles
which arrests water absorption into the AAC material is minimum.
It leads to Low maintenance and increased durability.
Recycle / Reuse :- Waste from the cutting process is recycled back
with raw materials and used again. During construction, there is
virtually no waste generated. AAC blocks can be reused into base
preparation of roads.

6. Types Of AAC Bricks.
AAC bricks are currently available in three sizes:-
1. Infill bricks: Size :- 600X600 mm.
Thickness :- 75,100,125,150,200 mm.
IMPORTANCE –
Easily replace 60% of the concrete in roof slabs. Saving significant
amounts of concrete, steel, labor, water, plaster etc

7. 2. Jumbo blocks:-
Size:- 600X200 mm.
Thickness:- 75,100,125,150, to 200 mm.
IMPORTANCE –
Because of large size less mortar is required. These bricks are
more suitable for multi-storied buildings etc.

8. 3. Thermal blocks:-
Size:- 300X200 mm.
Thickness:- 50 mm.
IMPORTANCE – Delay the transmission of heat flow. So, help
interiors remain warm during winters and cool during summers.
Good for roofing.

9. Different characteristics of AAC bricks.
The characteristics of bricks are as follows :-
1. Light-weight: Because of its aerated structure it become light in
weight. The weight is only one third the density of clay bricks, makes
them easy to handle on-site.
2. Fire resistance: Walls of AAC bricks, with a minimum thickness of
100mm can resist fire for up to 4 hours. Especially for industries and
companies, which are vulnerable to fire accidents, these blocks are of

10. 3. Sound insulation:
AAC brick can minimize the sound transmission up to 42 decibels.
Better for wall construction in hotels, auditoriums, Colleges, hospitals,
etc.
4. Thermal insulation:
The cellular structure of the AAC bricks provides excellent thermal
Insulation. Help interiors to remain cooler during summer and warmer
during winter.

11. 5. Strength and durability:
AAC bricks made with higher weight ratio help in building stronger and
economical structure. They remain unaffected by the environmental
conditions they ensure longer life for the building.
6. Perfect finish and dimensional stability:
Perfect dimensions to the blocks along with low tolerances.
Dimensionally perfect blocks help in building uniform, thin walls with
perfect finish.

12. Steps Involved in manufacturing process. There are mainly four steps
involves in manufacturing process of AAC Bricks:-
1. Raw Material Preparation:
Fly ash :-
Fly ash is mixed with water to form fly ash slurry. Fly Ash is usually a by-
product of thermal power plants and is an important raw material in the
manufacture of AAC Blocks. Slurry thus formed is mixed with other
ingredients like lime powder, cement, gypsum and Aluminium powder in
quantities consistent with the recipe.

13. Limestone powder:- Lime powder required for AAC
production is obtained either by crushing limestone to fine
powder at AAC factory or by directly purchasing it in powder
form from a vendor.
Cement :- 53-grade Ordinary Portland Cement (OPC) from reputed
manufacturer is required for manufacturing AAC blocks.
Gypsum :- Gypsum is easily available in the market and is used in
powder form.
Aluminium powder/paste :- A small quantity of Aluminium
powder/paste is required to be added to the mixture, it is usually
weighed manually and added to the mixing unit.

14. 2. Dosing and Mixing: -
Fly ash slurry is pumped into a separate container. Once the desired
weight is poured in, pumping is stopped.
Lime powder, cement and gypsum are poured into individual
containers using screw conveyors.
Mixing drum is like a giant bowl with a stirrer rotating inside to ensure
proper mixing of ingredients. Steam might also be fed to the unit to
maintain temperature in range of 40-42oC.
Dosing and mixing process is carried out continuously because if
there is a long gap between charging and discharging of ingredients,
residual mixture might start hardening and choke up the entire unit.

15. 3. Casting and Rising : -
Before casting, the moulds are coated with a thin layer of oil.
Done in order to ensure that cake does not stick to the
mould.
While slurry is mixed and poured into greased moulds,
Aluminium reacts with Calcium Hydroxide and water to form
Hydrogen.
Millions of tiny Hydrogen bubbles are released due to this
reaction. This leads to formation of tiny unconnected cells
causing slurry mix to expand.
These cells are the reason behind light weight and insulating

16. 4. Demoulding and Cutting:-
Once a mould is out of pre-curing room, it is lifted by a crane or
rolled on tracks for the demoulding operation.
Cutting operation is achieved by moving green cake through
horizontal cutting machine.
Horizontal or Vertical cuttings are made through cake using
stationary steel wires.
These wires can be adjusted offline to get desired height of AAC
blocks or panels.

18. s.n
o
Parameters AAC Bricks Clay Bricks
1 Soil Consumption. Zero soil consumption 1 square ft. of area with
clay brick walling will
consume 25.5 kg of top
soil.
2 Labour Organized sector with
proper HR practices.
Unorganized sector with
rampant use of child
Labour.
3 Production Facility State-of-the-art factory
facility.
Unhealthy working
conditions due to toxic
gases.
4 Compressive Strength. 3-4 N/m2 2.5-3 N/m2
5 Fire Resistance (8″ wall). Up to 7 hours Around 2 hours.
6 Cost Benefit Reduction in dead weight
leading to savings in steel
and concrete
None
7 Thermal Resistance. Approximately 30% for
heating and cooling
None
8 Speed of manufacturing HIGH LOW

19. CONCLUSION
However it is difficult to replace the old materials with new one.
Comparative Analysis indicates that in almost all the parameters, the AAC
blocks have a superior edge over burnt clay bricks.
The use of AAC blocks leads to savings in overall project cost; enables to
speed up the construction process reduced environmental and social
impact.
Therefore we can conclude that use of ACC blocks over burnt clay bricks is
recommended. It is advisable to developers, contractors, and individuals to

20. Thank you
By,
S.Abhisek