Page 32 - GRIHA Manual Volume IV - Introduction to National Rating System
P. 32
Building planning and construction 23
• Since CLC is chemically inert and stable, in case of fires, it does not let out any fumes when
compared with wooden partitions, which become a major cause of human casualties. It
has a high fire safety rating as well.
6. Autoclaved Aerated Concrete (AAC) blocks: AAC blocks are light weight concrete blocks, which
consist of fly ash, quick lime/cement, and a foaming/aeration agent like aluminium powder.
The constituents are mixed into slurry and steam-cured in autoclaves under high pressure.
The foaming agent produces bubbles of air, which get trapped in the blocks, thus, making
them lighter than other normal concrete blocks. The density of AAC is almost one-fifth of
the normal concrete. This helps in reducing the weight of the walls and partitions, which
results in savings in the structure of the building. The trapped air bubbles gives AAC better
insulation characteristics than other building blocks. The blocks have high fire-resistance
and are non-toxic.
The air bubbles trapped inside AAC gives AAC better thermal insulation properties than
concrete or bricks. Since AAC are completely inorganic, they do not let out any toxic fumes
in case of fire.
Advantages
• Light weight saves on foundation and structural costs.
• High fire-resistance and insulation (both thermal and acoustic).
• High durability.
• AAC blocks can be used in seismic and/or poor soil regions as well.
7. Fly ash-sand-lime-gypsum (cement) bricks/blocks: In these types of bricks/ blocks, fly ash can
be used in the range of 40%–70%. The other ingredients are lime, gypsum (cement), sand,
stone dust/chips, and so on. Minimum compressive strength (28 days) of 70 kg/cm can
2
2
easily be achieved and this can go up to 250 kg/cm (in autoclaved type).
Advantage of these bricks over burnt clay bricks
• Lower requirement of mortar in construction.
• Plastering over brick can be avoided.
• Controlled dimensions, edges, smooth and fine finish, and can be in different colours
(using pigments).
• Cost-effective, energy-efficient, and environment friendly (as avoids the use of fertile clay).
8. Clay-fly ash burnt bricks: A certain volume of clay in conventional clay burnt bricks can be
replaced by fly ash. Clay-fly ash bricks can contain 20%–60% fly ash depending upon the
quality of fly ash. Since fly ash is a pozzolanic material, these clay-fly ash bricks are stronger
than conventional burnt clay bricks. They are environmentally better since they consume
lesser energy to manufacture, provide better insulation, reduce the use of fertile clay for
manufacture of bricks, utilize industrial waste, and are cost-effective.
9. Fly ash bricks: Fly ash bricks are made of 100% fly ash and are fired in the same manner as
burnt clay bricks. They are a better alternative to clay bricks as they eliminate the use of
fertile top soil and clay, thereby reducing depletion of fertile land. Density of fly ash bricks
is 28% less than that of conventional burnt clay bricks.
• Since CLC is chemically inert and stable, in case of fires, it does not let out any fumes when
compared with wooden partitions, which become a major cause of human casualties. It
has a high fire safety rating as well.
6. Autoclaved Aerated Concrete (AAC) blocks: AAC blocks are light weight concrete blocks, which
consist of fly ash, quick lime/cement, and a foaming/aeration agent like aluminium powder.
The constituents are mixed into slurry and steam-cured in autoclaves under high pressure.
The foaming agent produces bubbles of air, which get trapped in the blocks, thus, making
them lighter than other normal concrete blocks. The density of AAC is almost one-fifth of
the normal concrete. This helps in reducing the weight of the walls and partitions, which
results in savings in the structure of the building. The trapped air bubbles gives AAC better
insulation characteristics than other building blocks. The blocks have high fire-resistance
and are non-toxic.
The air bubbles trapped inside AAC gives AAC better thermal insulation properties than
concrete or bricks. Since AAC are completely inorganic, they do not let out any toxic fumes
in case of fire.
Advantages
• Light weight saves on foundation and structural costs.
• High fire-resistance and insulation (both thermal and acoustic).
• High durability.
• AAC blocks can be used in seismic and/or poor soil regions as well.
7. Fly ash-sand-lime-gypsum (cement) bricks/blocks: In these types of bricks/ blocks, fly ash can
be used in the range of 40%–70%. The other ingredients are lime, gypsum (cement), sand,
stone dust/chips, and so on. Minimum compressive strength (28 days) of 70 kg/cm can
2
2
easily be achieved and this can go up to 250 kg/cm (in autoclaved type).
Advantage of these bricks over burnt clay bricks
• Lower requirement of mortar in construction.
• Plastering over brick can be avoided.
• Controlled dimensions, edges, smooth and fine finish, and can be in different colours
(using pigments).
• Cost-effective, energy-efficient, and environment friendly (as avoids the use of fertile clay).
8. Clay-fly ash burnt bricks: A certain volume of clay in conventional clay burnt bricks can be
replaced by fly ash. Clay-fly ash bricks can contain 20%–60% fly ash depending upon the
quality of fly ash. Since fly ash is a pozzolanic material, these clay-fly ash bricks are stronger
than conventional burnt clay bricks. They are environmentally better since they consume
lesser energy to manufacture, provide better insulation, reduce the use of fertile clay for
manufacture of bricks, utilize industrial waste, and are cost-effective.
9. Fly ash bricks: Fly ash bricks are made of 100% fly ash and are fired in the same manner as
burnt clay bricks. They are a better alternative to clay bricks as they eliminate the use of
fertile top soil and clay, thereby reducing depletion of fertile land. Density of fly ash bricks
is 28% less than that of conventional burnt clay bricks.
