AAC (Autoclaved Aerated Concrete)
blocks are made from a mixture of several key ingredients, including cement, lime, sand, aluminum powder, and water. The precise chemical composition can vary slightly depending on the manufacturer and specific product formulations, but the general composition of these ingredients is as follows:
AAC blocks typically contain ordinary Portland cement (OPC) as the primary binding agent. OPC is composed mainly of calcium silicates and aluminate compounds.
Lime is used in AAC production to improve the workability of the mix and to enhance the curing process. It also contributes to the overall chemical reaction that occurs during autoclaving (the process of curing AAC blocks under high pressure and temperature).
Sand is a major component of AAC blocks and provides the necessary structure and density to the material. It consists primarily of silica (SiO2) and may contain other minerals depending on its source.
Aluminum powder is a key ingredient that creates the characteristic lightweight and aerated structure of AAC. When aluminum powder reacts with calcium hydroxide and water, it generates hydrogen gas, which forms tiny bubbles within the mixture. These bubbles expand during autoclaving, resulting in a cellular structure.
Water: Water is essential for the hydration of the cement and lime, as well as for the reaction of aluminum powder to produce hydrogen gas. It is carefully measured to achieve the desired consistency of the AAC mix.
During the manufacturing process, these ingredients are mixed together to form a slurry or paste, which is then poured into molds. Afterward, the mixture is cured under high-pressure steam in autoclaves. This curing process is crucial because it allows the chemical reactions to take place, resulting in the formation of calcium silicate hydrates and the expansion of aluminum-generated bubbles. As a result, AAC blocks become lightweight, highly insulating, and structurally sound.
It's important to note that AAC block formulations may vary by manufacturer and intended use. Some manufacturers may include additives or modifiers to enhance specific properties or tailor the product for particular applications. Always refer to the manufacturer's specifications and documentation for detailed information on the chemical composition of a specific AAC block product.