Aerated concrete block is an important kind of construction material and it is mainly composed of cement, gravel, fly ash, lime and foaming agent. It possesses the advantages of light weight, fire prevention, thermal insulation,noise insulation, seismic resistance, environmental protection, etc. It is a certified green building material and can be used in commercial, industrial and residential construction projects. It is porous, non-toxic, reusable, renewable and recyclable.
Key ingredients for manufacturing Autoclaved Aerated Concrete (AAC) blocks arematerials rich in silica like fly ash, pond ash or sand. Most of the AAC companies in the world use fly ash to manufacture AAC blocks. Fly ash is mixed with water to form fly ash slurry. Slurry thus formed is mixed with other ingredients like lime powder, cement, gypsum and aluminium powder in quantities compliance with the recipe. Alternatively, sand can also be used to manufacture AAC blocks. A "wet" ball mill finely grinds sand with water converting it into sand slurry. Sand slurry is mixed with other ingredients just like fly ash slurry. Cement is an indispensable material in the filling block. In general, the ACC plants will choose Portland cement, which is usually stored in the stuff canister. Fly ash aerated concrete must prepare gas forming material as gas forming agent in order toproduce air hole in concrete and form a lightweight and porous structure. After the gas forming agentstarts generating gas, having considered the fact that thin wall of the air bubble is easy to break so as to affect the concrete quality, therefore, the slurry should be added some foam stabilizer.
When the raw materials have been prepared, they willbe sent to the central mixing station according to the pre-set formula. The most important equipment of the central mixing station is one or more mixers. The raw materials stored in the barrel will be fed into the mixer by a screw conveyor. The central control room can control the proportion of raw materials and the time of stirring. After the raw materials are stirred and mixed, next step can go on.
Casting, Rising and Pre-curing
After the raw materials are fully stirred by ACC mixing station, they will be poured into the mold, and the size of the mold may be various because of customers' different demand. In order to ensure that the filling block will not stick to the mold, the mold wall will be smeared with a layer of oil. Usually rising and pre-curing process takes around 60-240 minutes. Rising is dependent on raw material mix and weather conditions. For reaction is affected by weather conditions, it is recommended to maintain constant temperature in pre-curing area. Therefore, pre-curing is also referred as "heating room pre-curing".
Demoulding and cutting
Demoulding and cutting are very critical processes in AAC blocks manufacturing. These two processes play a major role in defining amount of rejection as well as dimensional accuracy of the final product. In most cases, after the AAC blocks cutting has been finished, they will be sent to the autoclave for steam curing, and then AAC blocks will be transported out by the steaming car.Till now, the whole production process is over.