Autoclaved aerated concrete block (AAC block) is a new type of wall material featured with lightweight and cellular structure. It is made of sand or fly ash, cement, and lime as the main raw materials. The AAC block making process contains several steps such as slurry mixing, pouring, molding, demolding, cutting, and curing by high-pressure steam in the autoclave. It is mainly used in non-load-bearing wall masonry and frame structure filling. It is a lightweight material popularized and applied in key industrial and civil fields.
What are the advantages & disadvantages of AAC blocks?
Advantages of AAC blocks
- Lightweight
Common aerated concrete blocks generally have a unit weight between 400-800kg/m, which is only equivalent to 1/4 or 1/3 of clay bricks and lime-sand bricks, and 1/5 of ordinary concrete. It is suitable for filling walls of high-rise buildings and load-bearing walls of low-rise buildings. Its self-weight is reduced by more than 40% compared with ordinary brick-concrete structures.
- Good heat insulation
The thermal conductivity of aerated concrete blocks is generally 0.11-0.18W/m K, which is only 1/4-1/5 of clay bricks and lime-sand bricks, and 1/6 of ordinary concrete. The thermal insulation performance is greatly improved.
- Strong earthquake resistance
AAC blocks have light bulk density and good overall performance. Certain deformation can be produced when the AAC blocks are squeezed to protect the whole from being damaged. The inertial force is small during earthquakes, so it has strong earthquake resistance.
- High-temperature resistance
The main raw materials of AAC blocks are mostly inorganic materials that have good fire resistance and do not emit harmful gases in case of fire. When the temperature is below 600 degrees, its compressive strength increases slightly. When the temperature is around 600 degrees, its compressive strength is close to that at normal temperature, reaching the national first-class refractory standard.
- Excellent sound insulation
The interior of the AAC block is a porous structure with a large number of closed pores evenly distributed, so it has sound-absorbing properties that general building materials do not have.
- Easy to process
AAC blocks are easy to process. It can be sawed, planed, nailed, milled, and drilled, which brings great convenience and flexibility to construction.
- A wide source of raw materials
The raw materials (sand, slag, fly ash, tailings, coal gangue, quicklime, cement, etc.) used in the production of AAC blocks are very common and are easy to find.
- High efficiency and energy saving
AAC blocks can be mass-produced in a highly automated manner, and the production efficiency is much higher than that of traditional building materials. In construction, it can save labor and materials, and can significantly speed up the construction period. Therefore, it is more efficient, more energy-saving, and more economical.
- Certain impermeability
AAC blocks are composed of many independent small pores, which absorb water and conduct moisture slowly. The time required to absorb water to saturation with the same volume is 5 times that of clay bricks. When used in the bathroom, the tiles can be pasted directly after the wall surface is treated with an interface.
- Environmental protection
AAC blocks use a lot of factory waste in the production process. It helps turn waste into treasure and effectively protects cultivated land by reducing the occupation of cultivated land. There is relatively little pollution in the process of manufacturing, transportation, and use, and it is a green and environmentally friendly building material.
Disadvantages of AAC blocks
1. The AAC block has large porosity and high water absorption. It is easy to leak after being immersed in water for a long time.
2. The construction requirements of the AAC block are relatively high. If the quality is not strictly controlled during the construction, the wall is prone to expansion and contraction cracks, and the post-processing is quite troublesome.
3. To effectively control the moisture content and shrinkage cracks of the wall when the AAC blocks are placed on the wall, the product age should not be less than 28d before use, and the moisture content should be less than 30%. It will bring great inconvenience to production enterprises and sales enterprises, and it is difficult to find a suitable place to stack the blocks.
4. The AAC blocks cannot be used in the key parts of the wall and the parts that require firmness. If it is used in doors, windows, and other parts, it must be reinforced, plugged, and sealed.
5. The surface hardness of the aerated block is not high, and it is easy to slag and powder. The adhesion of AAC blocks with the cement mortar is not ideal. If the operation is not good in the plastering stage, the plastering layer is easy to be hollowed out.
6. The surface strength of the AAC block is not high. It is highly brittle, and the corners and edges are easily knocked off, which affects the quality.
7. The AAC block is easy to shell and peel off in places where it is soaked in alternating wet and dry conditions for a long time.
What is the size & price of AAC blocks?
How much is the AAC block? Different specifications of AAC bricks have different prices. The price of the AAC block is calculated according to the square meter. Generally, the price of one square meter is about 200 yuan (about Rs 2287 / $ 28). There are also differences in prices in different regions. Different thicknesses will also lead to changes in the price.
The common size of AAC blocks on the market
| Length | Height | Width |
|---|---|---|
| 600 | 200, 250, 300 | 75, 100, 125, 150, 175, 200, 250 |
| 600 | 240, 300 | 60，120，180，240 |
| Other sizes upon request | ||
Where can AAC blocks be used?
Applicable places for AAC bricks:
1. AAC blocks apply to interior partition walls of mid-range buildings and higher-grade buildings.
2. AAC blocks apply to exterior walls, interior partition walls, and roofs of various steel structures and reinforced concrete structures in industrial and civil buildings.
3. It is suitable for the interior and exterior filling walls above the ground (±0.000) of various buildings and the interior filling walls below the ground (except for walls with special requirements).
Precautions for the application of AAC bricks
1. AAC bricks are not suitable for long-term water immersion or frequent wet and dry parts, such as toilets, showers, balconies, etc.
2. AAC bricks are not suitable for use in environments subject to chemical corrosion, such as environments with strong acids, strong alkalis, or high concentrations of carbon dioxide.
3. AAC bricks are not suitable for use in high-temperature environments where the masonry surface is often above 80°C.
4. AAC bricks are not suitable for use in buildings below ±0.000 (except for indoor filling walls in basements).
5. AAC bricks are not suitable for walls that have been exposed to vibration sources for a long time.
What are the differences between AAC blocks & red clay bricks?
Red bricks are also called clay bricks, which use clay, coal gangue, etc. as the main raw materials. After crushing and mixing, they are manually or machine pressed into shape, and then oxidized and fired at high temperature (900 degrees Celsius) to form sintered bricks. The main differences between AAC blocks and red clay bricks:
- Different materials
The materials of AAC blocks are cement, lime, sand, foaming agent, etc., while the materials of clay hollow bricks are fired from natural clay. Therefore, AAC blocks are stronger and more durable than clay hollow blocks.
- Different weight
AAC blocks are lighter than clay hollow bricks, generally weighing 2-3 kg per block, while clay hollow bricks weigh about 3-4 kg. Therefore, at the time of construction, the aerated concrete block is more convenient and the transportation cost is lower.
- The difficulty of construction
Clay hollow bricks need to pay special attention to the gap and verticality when building the wall to ensure the quality of the entire wall. However, due to the more uniform material quality of the AAC block, it is easy to build a wall with better verticality. Therefore, in comparison, AAC blocks are easier to construct.
- The insulation performance
AAC blocks have good thermal insulation properties because of the large number of holes inside them. It can be chosen for families with thermal insulation problems. The clay hollow brick is slightly inferior in terms of thermal insulation performance, and it is necessary to increase the thermal insulation layer to improve the thermal insulation effect.
