AAC blocks are Autoclaved Aerated Concrete blocks. They are cutting-edge and adaptable building materials that have several benefits over conventional building supplies. Cement, sand or fly ash, gypsum, lime, water, and an expanding agent—typically aluminum powder—are the ingredients used to make them.
Hydrogen gas is produced when lime and aluminum powder are combined. By introducing microscopic air bubbles into the mixture, this gas produces a light cellular structure. The mixture is put in an autoclave, which is a high-pressure steam chamber, where it goes through curing to speed up this process.
The conditions required for the creation of AAC are provided by the autoclaving procedure. The combination expands even more when exposed to high-pressure steam, and the chemical reaction between the aluminum powder and lime produces calcium silicate hydrate, which provides the substance its tensile strength and durability.
Steps for manufacturing AAC blocks
The manufacturing of AAC blocks goes through the following steps:
- Raw material preparation
A: Siliceous materials: Fly ash / Sand /Tailings containing silicon
B: Calcareous material: Lime block + cement + gypsum
C: Gas former: Aluminum powder
Key materials for manufacturing the autoclaved aerated concrete are fly ash and sand. They are ground to fine materials by ball mills and then mixed with water to form a slurry. This slurry is stored in the slurry tank and will be mixed with other ingredients in the next step of raw material dosing.
Other ingredients such as Lime block, cement, and gypsum are also ground to fine powders and stored in separate silos prepared for the dosing and mixing.
- Dosing & mixing
This is a crucial step for the quality of finished AAC blocks or panels. Flyas/sand slurry is pumped into a mixing drum. The lime powder, cement, and gypsum are fed into the mixing drum through screw conveyors. Aluminum powder is pretreated and will be added before pouring. All the raw materials are mixed in the mixing drum with an appropriate ratio. The ratio of AAC ingredients is controlled by a centralized computer control batching system. Next, the mixed slurry will be poured into the molds.
- Casting rising and curing
The correct proportioned raw materials are poured into molds. The molds are coated with oil in advance to prevent stickiness. Bubbles are eliminated in this process.
The slurry mix is expanded with bubbles because of the chemical reaction between aluminum powder and lime and water. The slurry gets hard in the molds after about 1.5-2 hours under a temperature of about 50-70 ℃. The time for pre-curing varied in different weather conditions. After pre-curing, the green cake is hard enough for cutting.
- Demolding & Cutting
After a 90-degree tilt, the tilting crane raises the mold and releases the green cake. The green cake is then sliced using horizontal and vertical cutting machines. It is lifted to the turning and peeling mechanism before entering into autoclaves, and the bottom trash is recycled.
The hauling machine transfers and stacks the side plate and slices green cake on tracks before placing them into the autoclave. The AAC blocks are heated to assure the finished blocks’ chemical composition and hardness. The autoclave curing process will take 8 to 12 hours.
- Out autoclave
The out-autoclave process is the last in the production of aerated concrete, including the exiting, lifting, splitting(panel’s process), inspection, and packaging of aerated concrete products. The process of leaving the autoclave is the guarantee for us to provide qualified products to the market and the normal progress of the next production cycle.
Advantages of AAC blocks
Lightweight: Since AAC blocks are portable and simple to handle, they are perfect for building projects where speed and simplicity of installation are crucial.
Thermal insulation: AAC blocks provide superior thermal insulation qualities that can save energy expenditures and increase a building’s energy efficiency.
Fire-resistant: AAC blocks are perfect for usage in structures where fire safety is a concern because of their outstanding fire-resistant qualities.
Sound insulation: AAC blocks offer excellent sound insulation qualities, which can assist lower noise levels in buildings and make living or working spaces more pleasant.
Durable: AAC blocks may survive for many years without the need for maintenance or repairs since they are durable.
Eco-friendly: Environmentally friendly: AAC blocks are built of natural resources and are regarded as environmentally friendly construction materials.
Cost-effective: AAC blocks are a good option for construction since they are affordable.
Versatility: Buildings for use as homes, businesses, or factories, as well as bridges and other infrastructure projects, can all be constructed with AAC blocks.
Autoclaved Aerated Concrete (AAC) has gained popularity because of its numerous advantages. Overall, AAC block is a substitute for traditional building materials due to its excellent thermal and sound insulation, fire resistance, durability, and sustainability. AAC is a well-established and widely used building material in modern projects especially for its lightweight nature and ease of handling.