Autoclaved Aerated Concrete | Autoclaved Aerated Concrete Advantages & Disadvantages
Autoclaved Aerated Concrete
What Is Autoclaved Aerated Concrete?
Autoclaved Aerated Concrete (AAC) is a precast, lightweight foam concrete material that is ideal for making concrete masonry unit (CMU)-like blocks. AAC products are made up of quartz sand, calcined gypsum, lime, cement, water, and aluminum powder.
They are cured in an autoclave using heat and pressure. Autoclaved Aerated Concrete was invented over 800 years ago and provides structure, insulation, and resistance to fire and mold.
Blocks, wall panels, floor and roof panels, cladding (façade) panels, and lintels are all possible configurations.
Autoclaved Aerated Concrete products can be used for both interior and exterior construction and can be protected against the weather by painting or coating them with stucco or plaster compound or by covering them with siding materials such as veneer brick or vinyl siding
Apart from their ease of installation, Autoclaved Aerated Concrete materials can be routed, sanded, or cut to size on-site with ordinary power equipment equipped with carbon steel cutters.
Autoclaved Aerated Concrete Application/Uses
Autoclaved Aerated Concrete (AAC) is a highly insulating concrete-based substance that is utilized both inside and outside of buildings.
Apart from its insulating properties, another advantage of AAC is its speed and ease of installation, since the material can be routed, sanded, or cut to size on-site using normal power tools equipped with carbon steel cutters.
Autoclaved Aerated Concrete (AAC) is well-suited for high-rise structures and those subjected to extreme temperature fluctuations. As a result of its lower density, AAC-clad high-rise structures require less steel and concrete for structural components.
Due to the reduced number of joints, the mortars required for laying Autoclaved Aerated Concrete (AAC) blocks are lowered. Similarly, the amount of material required for rendering is reduced due to the accuracy of Autoclaved Aerated Concrete’s dimensions (AAC).
AAC’s higher thermal efficiency qualifies it for usage in places subject to extreme temperatures, as it removes the need for separate building and insulation materials, resulting in speedier construction and cost savings.
While conventional cement mortar may be utilized, the majority of structures constructed using AAC materials employ thin bed mortar with a thickness of approximately 3.2 millimetres (18 in), depending on the national building requirements.
To protect against the elements, Autoclaved Aerated Concrete (AAC) materials can be coated with a stucco or plaster compound or covered with siding materials such as brick or vinyl.
What is Autoclaved Aerated Concrete Made of?
AAC is manufactured of fine aggregates, cement, and an expansion ingredient that makes the fresh mixture to rise like bread dough. Indeed, this form of concrete includes approximately 80% air.
Unlike most other types of concrete, Autoclaved Aerated Concrete is made entirely of with no aggregate larger than sand. As a binder, quartz sand, calcined gypsum, lime (mineral) and/or cement are employed. Aluminum powder is utilized at a concentration of 0.05–0.08% by volume.
In some countries, such as India and China, fly ash from coal-fired power plants with a silica level of 50–65 percent is utilized as an aggregate.
When Autoclaved Aerated Concrete is prepared and cast into forms, a series of chemical processes occur that contribute to the material’s light weight (20% of the weight of concrete) and thermal characteristics.
Aluminum powder forms hydrogen when it combines with calcium hydroxide and water. Hydrogen gas foams and doubles the volume of the raw materials, forming gas bubbles up to 3 millimeters (18 mm) in diameter.
The hydrogen escapes into the environment and is replaced by air at the conclusion of the foaming phase.
When the forms are removed from the material, it becomes solid but retains its soft characteristics. It is then chopped into blocks or panels and placed in a 12-hour autoclave chamber.
When the temperature reaches 190 degrees Celsius (374 degrees Fahrenheit) and the pressure reaches 8 to 12 bars (800 to 1,200 kPa; 120 to 170 psi), quartz sand interacts with calcium hydroxide to generate calcium silicate hydrate, which provides Autoclaved Aerated Concrete with its high strength and other distinctive qualities.
Due to the low temperature at which Autoclaved Aerated Concrete blocks are manufactured, they are not called burnt brick but rather a lightweight concrete masonry unit.
After autoclaving, the material is immediately available for use on the construction site. Up to 80% of the volume of an AAC block contains air, depending on its density.
Thin bed mortar is used to bind cured blocks or panels of autoclaved aerated concrete. Components may be utilized in the construction of walls, floors, and roofs.
The lightweight material provides superior sound and thermal insulation and, like all cement-based materials, is durable and fire resistant.
AAC requires an applied finish, such as polymer-modified stucco, natural or synthetic stone, or siding, in order to be durable.
What Is Another Name for Aerated Autoclaved Concrete?
Additionally, the product is known as autoclaved cellular concrete (ACC), cellular concrete, autoclaved lightweight concrete (ALC), porous concrete, Siporex, Aircrete, Thermalite, autoclaved concrete, Hebel Block, Starken, and Ytong.
Is Autoclaved Aerated Concrete a Strong Material?
Although autoclaved aerated concrete is robust enough to be used in structural components of a structure, it is not as strong as ordinary concrete.
The Portland Cement Association specifies an allowed shear stress of 8 to 22 psi and a compressive strength of 300 to 900 psi for autoclaved aerated concrete.
Is Autoclaved Aerated Concrete Blocks Better than Brick?
Red clay bricks are an excellent choice for small-scale projects that do not require higher compressive strength or better handling and workability.
However, autoclaved aerated concrete blocks provide superior performance and quality for high-rise, industrial, commercial, and infrastructure projects.
Does AAC Blocks Require Plastering?
When compared to standard bricks, these blocks allow for up to five times faster speed. Additionally, the even surfaced wall requires relatively little plaster on both sides, which is a very cement intensive material, resulting in significant cost savings.
Why Do Autoclaved Aerated Concrete Blocks Get Cracks?
While all concrete blocks are susceptible to cracking, some procedures might help prevent their occurrence.
Several factors contribute to such cracking, including beam deflection, uneven block placement, structural movement caused by thermal expansion or changes in moisture content.
Advantages of Autoclaved Aerated Concrete
Autoclaved Aerated Concrete has been manufactured for over 70 years and has a number of advantages over other cement-based construction materials, the most significant of which is its reduced environmental effect.
- Increased thermal efficiency minimizes a building’s heating and cooling burden.
- Workability enables precise cutting, which reduces the amount of solid waste generated during use.
- Superior fire resistance is provided by the porous construction.
- Due to their light weight, the blocks are readily handled.
- Reduces the cost of massive construction projects.
- Resource efficiency enables it to have a lesser environmental impact throughout its life cycle, from raw material processing through waste disposal.
- Lightweight construction reduces transportation costs and energy consumption, as well as labor costs, and increases the likelihood of surviving during earthquake activity.
- Larger block sizes result in faster masonry operations.
- Environmentally responsible: It generates up to 30% less solid waste than conventional concrete. There is a 50% reduction in greenhouse gas emissions.
- Non-hazardous: Autoclaved aerated concrete contains no poisonous fumes or other harmful components. It is not attracted to rats or other pests and cannot be harmed by them.
- Excellent ventilation: This material is extremely breathable and enables for water diffusion. This decreases the humidity level within the building. Aerated Concrete that has been autoclaved will absorb moisture and release it. This helps avoid condensation and other mildew-related problems.
- Fire safety: It is a first-class fire-resistant material that outperforms ordinary concrete in terms of combustibility, as Autoclaved Aerated Concrete is non-combustible.
- Accuracy: Before leaving the factory, the panels and blocks constructed of autoclaved aerated concrete are manufactured to the exact dimensions required. On-site pruning is not required as often. Because the blocks and panels fit together so perfectly, finishing materials such as mortar are not required.
- Autoclaved Aerated Concrete, like conventional concrete, is fire resistant.
- This material has a long life since it is not influenced by harsh climates or strong weather fluctuations. It will not deteriorate as a result of typical climate fluctuations.
Disadvantages of Autoclaved Aerated Concrete
Although autoclaved aerated concrete has been manufactured for over 70 years, it has some significant limitations. These includes
- Installation in wet weather: Autoclaved Aerated Concrete is known to crack following installation. This can be avoided by lowering the strength of the mortar and ensuring that the blocks remain dry throughout and after installation.
- Due to their brittle nature, they require more care than clay bricks to avoid breaking.
- Attachments: The brittle nature of the blocks necessitates using longer, thinner screws and wood-compatible drill bits or hammering in when installing cabinets and wall hangings. Special big diameter wall plugs (anchors) are more expensive than standard wall plugs.
- Insulation standards in contemporary construction codes in northern European countries would necessitate extremely thick walls if Autoclaved Aerated Concrete were used exclusively. As a result, many builders opt for traditional construction methods, which include adding an additional layer of insulation to the entire structure.