Materials in producing AAC bricks include: silica sand (or siliceous ash), lime, plaster, concrete and aluminum powder. Main stages as below diagram:

 Diagram of producing AAC bricks

  1. Quantification
  2. Mixing
  3. Filling into the molds
  4. Vulcanization
  5. Cross bar cutting
  6. Putting into autoclaved aerated digesters
  7. Taking finished products and transportation

Lime’s role in ACC manufacturing

Lime is an important component of ACC, making up about 15% volume of raw materials in ACC’s production. Firstly, lime is mixed equally with other materials, after reacting with water; it’ll be dissolved as the following reaction:

CaO + H2O =  Ca(OH)2

When added into the mixture, aluminum powder react with Ca(OH)2 to create millions of tiny hydrogen gas bubbles distributed equally in concrete structure as follows:

2Al + Ca(OH) + 2H2O = Ca(AlO2)2 + 3H2

Besides, lime mainly effects to create substance calcium silicate hydrate (CSH) during autoclave process at temperature of 170-180 Celsius degree and atmosphere of 8-12 atm. At this temperature and pressure, quartz SiO2 becomes active SiO2 creating CSH then increasing atmosphere concrete strength after autoclave as below reaction:

Ca(OH)2 + SiO2ht = CaO.SiO2.H2O(genCSH)

Lime specification

  • Degree of fineness after crushing: <0.08
  • Cao content: >80%
  • Slaking time: >3 mins
  • Slaking temperature: 60-90oC