Force Engineering - AAC Plant Manufacturer

Raw Materials Processing System

AAC system is depend on varieties of raw materials.

The main systems used in the area of raw materials processing include:

Fly ash feeding with dosing devices

Ball mills for wet grinding

Sludge tanks with agitators

Silos for solids

Aluminium plants

A variety of raw materials can be used for AAC production. It is usually finely ground, silicate-rich quartz sand, quicklime, cement and anhydrite or gypsum (as binders), as well as aluminium paste or powder (as foaming agent) and water. Fly ash is a popular alternative to sand. In the storage silos, the solids (quicklime, cement and anhydrite (gypsum)) are intermittently stored. The silos are equipped with discharge devices that ensure an even and controlled emptying of the silo.In the aluminium plant, the aluminium paste is dosed either batch-wise or daily quantity-wise before it is mixed with water and fed to the mixer. All the system components used are equipped with filling level monitors.

Chemistry Of AAC Mixing Proportion

The combination of cement, lime, gypsum (anhydrite),fly ash, finely ground sand and most importantly aluminium powder togetherly forms AAC formulation. It causes the mixture to expand considerably. From the beginning to the end the simplified chemical reactions look as follows:

CaO+H2O Ca(OH)2 + 65,2 KJ/mol
3Ca(OH)2 + 2Al + 6H2O Ca3(Al(OH)6)2 + 3H2
6SiO2 + 5Ca(OH)2 5CaO . 6SiO2 . 5H2O

There are two types of autoclaved aerated concrete (AAC) production methods which are chemical and mechanical processes. In the chemical process, some metallic compounds would be added to react and generate tremendous amount of air bubbles in concrete texture while in mechanical process expansive foaming agent is normally employed. In general, AAC could be prepared in a high pressure autoclave under conditions of temperature and pressure higher than 180oC and 12 bar, respectively. Approximately the porosity is 80% of the volume of the processed cement, resulting in its very light weight.