What Are AAC Cement Bricks?
AAC Cement Bricks are a precast and lightweight building material that also provides safe structure, insulation, and fire and mold resistance. AAC Block is a unique type of construction material due to its excellent heat, fire, and sound resistance.
In AAC Cement Bricks prime ingredients are fly ash, cement, water, quicklime, aluminum powder, and gypsum. The cement strength provides hardness to block and instant curing mechanism by autoclaving.
Gypsum provides long-term strength to the block. The aluminum paste chemical reaction provides AAC with its distinct porous structure, lightness, and insulation properties.
Read More: Standard Brick Size
Important Points About AAC Block
The AAC block is 2.5 times lighter compared to conventional Bricks while providing similar strengths and specific gravity stays around 0.6 to 0.65.
AAC blocks offer around 30 to 35 % savings on structural steel, and concrete, as these blocks reduce the dead load on the building significantly. It is a long-run and durable material.
It has been used in EUROPE for over 90 years for commercial, industrial, and residential applications and the Middle East for the past 40 years, and in America and Australia for 25 years.
The report says that AAC block now accounts for over 40% of all construction in the UK and more than 60% of construction in Germany.
The Indian company started the production of the AAC block in late 1972.
Read More: Which Cement Is Best For House Construction
Manufacturing Process of AAC Cement Block
Step: 1 Raw Material Preparation
1. Coal fly ash
Fly ash is filled in slurry preparing pond by wheel loader. Where fly ash slurry is prepared of concentration adding rated water, which will be pumped into slurry tank to be stored and ready to be used.
2. Quick Lime
The active lime powder is stored in a lime silo and ready to be used by bucket elevator, after coming into the factory.
It is stored in the upper shed and will be added to the slurry pond according to the required proportion while preparing a slurry.
Cement is received by trucks and directly pumped into a cement silo to be used.
5. Aluminum Powder Paste
The aluminum powder was added to the mixer to prepare the 5% suspending liquid to be used.
Step 2 – Dosing and Mixing
It is the process of assuring the quality of the product by adding an accurate amount of raw material to a mixer. Maintaining the ratio of all ingredients as –
FLY ASH OR SAND: LIME: CEMENT: GYPSUM = 69:20:8:3
- Aluminum is about 0.05% of total dry materials in the mix
- Water ratio = 0.60-0.65
- The cycle of mixing and pouring is 5.5 minutes.
For this mixing fly, ash is filled in the container and as the desired weight is poured in, pumping is stopped. In a similar manner cement, lime powder, and gypsum are poured into individual containers using conveyors.
Once all materials are filled in their individual container in the required amount system releases all ingredients into the mixing drum.
For aluminum powder feeding smaller bowl-type structure is also attached as a part of the mixing unit. Once the mixing of all materials is done for a specified time, the mix is ready to pour into molds. A dosing unit fills a set quantity of mix into each mold.
This process must be continuous without a significant long time; otherwise, if there is a gap between the charging and discharging of ingredients, the residual mixture might start hardening and choke up the entire unit.
This process is completely automated and requires minimum human intervention.
Step 3 – Casting, Rising, and Curing
After the above raw material mix is ready to be poured is in molds. AAC block molds can be of various sizes depending upon installed capacity like 4.2m x 1.2m x 0.65m in size.
Before pouring the mold with the mix, molds are coated with a thin layer of oil in order to ensure that the green cake does not stick to the molds.
As we pour the slurry into a mold, Aluminum reacts with Calcium Hydroxide and water and releases hydrogen gas.
It leads to the formation of a small air pocket in the block. The air bubble size is about 2- 5mm.
This is the major reason behind the lightweight and insulating properties of the AAC block. After all this process is completed, the resulting product is to be cured for at least 9 days after casting.
Step 4 – De-moulding and Cutting
Once a block has achieved cutting strength, it is ready to be remolded and cut as per requirements.
AAC blocks are manufactured in the long-length strip during casting and then it is cut to the required size and shape.
Size and shape totally on market demand. Block-cutting technologies also differ from machine unit providers.
Advantages of AAC Cement Block
The advantages are as follows
1. Fly is the main constituent in AAC Block manufacturing, which is a big problem for thermal power plants to dispose of. The reuse of fly is environment-friendly as no need to dispose of them anywhere else.
2. AAC Block has better strength properties, best thermal insulation & excellent sound absorption, and vibration resistance compared to red bricks.
The AAC blocks are lightweight and offer easy and quick handling and transportation with lesser breakage.
3. Wall made with AAC Block can be left clean without plaster and gains strength over time. It helps in reducing structural costs by 35%.
4. There is no effect of harsh climatic conditions on AAC blocks and will not degrade under normal atmospheric conditions.
5. It does not have any toxic substances nor does it emit odors. AAC block production, management, and disposal do not represent any health risks or damage to the environment. Its manufacturing process develops non-toxic gases.
6. Compare to conventional bricks, the AAC block has a bigger size resulting in a lesser number of joints. Less joint means less use of mortar for wall construction.
AAC Block Vs Clay Bricks Comparison
|Property||Units||AAC Block||Clay Brick|
|Size||mm||600 x 200 x (75 to 300),||230 x 75 x 115|
|Size Tolerance||mm||± 1.5||± 05 to 15|
|Compressive Strength||N/mm2||3 – 4.5 (IS 2185 part 3)||2.5 to 3.5|
|Normal Dry Density||Kg / m3||550 – 650||1800|
|Sound Reduction Index||Db||45 for 200 mm Thick Wall||50 for 230 mm Thick Wall|
|Fire Resistance||Hrs.||2 to 6 (Depending on Thickness)||2|
|Thermal Conductivity “K”||W / m-k||0.16 – 0.18||0.81|
|Drying Shrinkage||%||0.04% (Size of block)||–|
|Parameter||AAC Block||Clay Bricks|
|Structural Cost||Steel Saving Upto 15%||No Saving|
|Cement Mortar (plastering and masonry work)||Less Required due to flat, even surfaces & less number of joints||More required due to the irregular surface and the number of joints.|
|Breakage||5% less||10 to 12 % Average|
|Construction speed||Speedy construction due to its big size, lightweight & easy to cut in any size or shape||Comparatively slow|
|Quality||Uniform & Consistent||Normally varies|
|Chasing & Fitting||fitting and chasing possible||fitting and chasing possible|
|Carpet Area||The thickness of walling material is less so more area available||Comparatively low|
|Availability||Anytime||Shortage in monsoon|
|Energy Saving||Approx. 30% reduction in air-conditioned load||No such saving|
|Chemical Composition||Sand/Flyash used around 60 – 70 % which reacts with Lime & Cement to form AAC||Soil is used which contains many inorganic impurities like sulphates etc. resulting in efflorescence|
AAC Cement Block Price Vs Clay Brick Price
- AAC Cement Block Price: Rs. 2000 to 3000 per Cubic meter or Rs. 30 to 40 per Block
- Red Clay Brick: Rs. 4 to 6 per Brick
AAC Fly Ash Bricks Price
AAC fly ash brick price starts from Rs. 5.80 per Piece
From the comparative study, it is acknowledged that the AAC blocks have a superior edge over burnt clay bricks.
The AAC blocks use in building construction lead to savings in overall project cost; enabling speed of the construction process and reduced environmental and social impact.
Therefore we can say that AAC block use is a better choice for building construction compared to red burnt clay bricks. It is advisable for contractors, builders, and individuals to encourage this product as its use is in the national interest.
Watch Video: AAC Block vs Red Bricks Which is Better?
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