AAC or Autoclaved aerated concrete is in the sense of concrete made by air which in these blocks lightens the block by using gas bubbles, this process is done when the cement slurry is produced by aluminum powder in the mixer and puff to produce the final form of the light block.
Previously it is used calcium carbide + aluminum as well as calcium chloride + oxygenated water to make the puff but oxygen gas is created by using aluminum powder, hydrogen gas with calcium carbide, acetylene gas and oxygenated water. Today, one of these methods is used because acetylene gas is flammable and oxygenated water is expensive.
Necessary materials for each cubic meter:
0.5 kg of aluminum powder
400 kg silica sand
140 kg of quick lime powder
35 kg of cement
after mixing these amounts, Water is added to it and the puffing and chemical reaction begins, at this stage, the concrete volume is increased to three times. After that, the blocks are cut with wire and then transferred to an autoclave where it is pressed at steam pressure of 8 to 10 bar at 230 ° C. In the autoclave part due to the pressure, quick lime slaked. It effects on the surface of silica sand grains and forms calcium silicate. on the other hand, at the same pressure, the aluminum powder, with water vapor and lime slaked and releases hydrogen gas, which gives the following reaction.
2Al + 3Ca(OH)2 = Al2O3.3CaO + 6H
Then the released hydrogen gas penetrates into the concrete and empties it. This concrete is called the Ytong block, which has a spatial weight of 3770 kg / m 3 and a 28-day compressive strength of 6 N / mm 2.شنبه ۲۷-۰۵-۱۳۹۷