Autoclaved Aerated Concrete, also known as Autoclaved Lightweight Concrete (ALC), is an eco-friendly and certified green building material. Basically, AAC is a mixture of cement, fly ash, sand, water and aluminium powder.
AAC panels or AAC blocks are a lightweight, load-bearing, durable, eco-friendly and cost-effective alternative to traditional building materials. AAC panels can be customised to meet dimensional demands.
Compared with concrete, wood, brick and stone, AAC panels and blocks have excellent insulation, fire and thermal resistance properties. In addition to this, it can increase the speed of construction and reduce costs.
The main ingredients of AAC panels are fly ash, sand, cement, lime, gypsum, water and aluminum powder. Aluminum powder serves as a foaming agent.
The cement used to make AAC panels and blocks is OPC43 or OPC53 grade cement, used as a binding material.
Fly ash is industrial waste from a power plant. Its density ranges from 600 kg/cm3 to 1400 kg/cm3. The existence of fly ash gives AAC blocks their insulation and fire resistance properties.
Lime is acquired by grinding limestone at block manufacturing plants or outsourced as lime powder.
Aluminum comes in as a foaming agent and takes care of the formation of voids within the panels and blocks.
Gypsum is a type of industrial waste produced in fertilizer plants and is available in large quantities.
The manufacturing process of AAC panels and blocks is related to a series of operations. Each stage is tied with strict manufacturing quality guidelines to ensure the necessary strength and density. The AAC product manufacturing process is broadly divided into the following processes.
Static stop maintenance
The raw materials used in the production of aerated concrete are firstly transported into the factory by various vehicles and stored in the warehouse or the material yard.
Then siliceous materials such as sand and fly ash are finely ground in a ball miller and then stored in the powder lime silo; aluminum powder is regularly purchased and stored in a cool and dry warehouse every month according to the plan.
The stockpile of raw materials is mainly to ensure the continuity of production and stability, in order to meet the process requirements and produce qualified products.
In the case of producing AAC panels, there is an additional process of steel processing and rebar mesh assembly. Steel processing is a unique process in the production of AAC panels, including rust removal, straightening, cutting, welding, coating preparation, coating impregnation and drying of steel bars.
The reinforcing mesh assembly process is to assemble the corrosion-treated reinforcing mesh into the mold according to the size and relative position required by the process, and to make it fixed for pouring and the formation of slurry gas.
Dosing is to measure the prepared raw materials according to certain requirements and store them temporarily in different containers, then add materials to the mixing equipment in the order required by the production process, in order to carry out the pouring operation.
Dosing is a very critical part of the production process of aerated concrete, which is related to whether the ingredients are reasonable, and has an important impact on the process of gas generation, hardening process and the final performance of the products.
The pouring process is to put the materials into the pouring car, and after stirring by the pouring machine, make the mixed slurry to the time, temperature and consistency required by the production process. And then pour it into the mold, followed by the static stop maintenance process to form the billet.
After all kinds of materials are put into the pouring truck, a series of preliminary chemical reactions will take place. The pouring process is an important process for aerated concrete to form a good porous structure.
Static stop maintenance is mainly to promote the mixed slurry to continue with gas expansion thickening, and eventually, the blank can grow taller and harden in the mold, so that the aerated concrete can achieve a certain cutting strength, which is convenient for cutting and processing.
The static stop maintenance process generally does not have too many operations, most manufacturers attach great importance to the impact of the ambient temperature, so there are facilities to adjust the temperature.
Cutting is the division and appearance processing of aerated concrete embryos. By using a special cutting machine, the size and appearance of aerated concrete products can be flexible and varied, thus meeting users' diverse needs.
The working condition of the cutting machine not only directly determines the quality of AAC products, but also affects the efficiency of the whole production line. Therefore, the cutting process must be highly concerned in the manufacturing process of AAC products.
The autoclave process provides AAC blocks with ideal durability and structural stability. The suitable temperature for autoclaving is above 175 ℃. Under such high temperature, high humidity and airtight conditions, the internal hydration reaction of aerated concrete blanks will be sufficient, generating the required hydrates to form the required strength.
The autoclave operation should be handled with proper specification, otherwise, some problems will occur, and even affect the finished product rate.
Discharging is the last process of AAC production, including discharging, lifting, breaking, inspection and packing of AAC products. The discharging process is the guarantee for us to provide qualified products to the market and for the normal operation of the next production cycle.