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What Materials Are AAC Blocks Made Of?

AAC blocks are a new type of building material gaining more and more popularity in the world. The full name of the AAC block is the autoclaved aerated block. The manufacturing of (AAC blocks) is rich in raw materials, especially the use of fly ash as raw materials. It can not only comprehensively utilize industrial waste residues, control environmental pollution, and not damage cultivated land, but also create good social and economic benefits. It is an ideal wall material alternative to traditional solid clay bricks.

aac block component
new building material-aac blocks

Various raw materials play a very important role in the making process of autoclaved aerated concrete blocks. Raw materials that pass the quality standard are important indicators that determine the high yield of AAC blocks produced. If the yield is high, our income will be high. In this article, we will take a look at the raw materials of AAC blocks and the role of various raw materials in the production process.

Raw materials for making AAC blocks

Fly ash

Fly ash is the core raw material and the main source of silicon-aluminum components in aerated concrete products. It provides siliceous material to react with CaO in calcareous material to form a hydration product, which contributes to the strength of the AAC blocks. Fly ash can also be used as a skeleton to reduce the shrinkage of concrete products.

aac block raw material fly ash
fly ash

Cement

Cement is the main source of strength of fly ash made AAC blocks. It provides the main calcareous material for aerated concrete. The main function of cement is to ensure the stability of pouring and accelerate the hardening of the green body and the plastic strength of the green body during cutting.

aac block raw material cement
cement

Lime

Lime is calcined and decomposed by limestone at 900-1300°C, and its main component is CaO, namely quicklime. Its function is to provide calcium components, react with active SiO2 and Al2O3 in fly ash under hydrothermal conditions, and generate crystalline or colloidal hydrated calcium silicate and calcium aluminosilicate products so that the aerated block has a certain strength and other properties. Lime also provides alkalinity, making it gassy with aluminum paste. When the lime is hydrated, heat is released, which promotes the hardening of the green body.

aac block raw material lime
lime

Gypsum


Gypsum is a regulator of the gas generation process in fly ash aerated concrete. The regulating effect of gypsum is mainly reflected in the delay of quicklime digestion and slurry thickening speed. The main chemical component of gypsum is CaSO4. Currently, there are three types of gypsum on the market: raw gypsum, anhydrite, and plaster of Paris. In addition, waste gypsum is also produced in the chemical production process. Such as phosphogypsum discharged from phosphate fertilizer production, fluorine gypsum discharged from fluorine chemical production, titanium dioxide gypsum discharged from titanium dioxide production, etc. These gypsums are low in cost and can replace natural gypsum, reducing production costs.

aac block raw material gypsum
gypsum

Water

The purpose of adding water is to ensure that the components of the slurry can be stirred evenly, to ensure that the slurry can be poured into the mold smoothly and that gas generation and initial setting can be performed normally. Whether the amount of water is used well can affect the gas generation and condensation process of the slurry, and finally affect the pore structure of the material. Adding too much water will make the slurry too thin, and the reaction between aluminum powder and calcium hydroxide will be accelerated. At the same time, the setting time of the aerated concrete slurry will be prolonged, resulting in the out-of-synchronization of the gas generation and setting time, resulting in the sinking and boiling of the slurry, resulting in aerated concrete. The pore structure of concrete is destroyed, which affects the quality of the product. If the water consumption is too small, in addition to the influence of stirring and pouring, the slurry will condense prematurely before the end of the gas generation process. In severe cases, the gas generation of the slurry will be insufficient, resulting in cracking of the product.

Foam stabilizer

It is a surface-active substance that reduces surface tension. When the concentration of the foam stabilizer increases, the surface tension decreases a lot. When the concentration is reached, the surface tension no longer changes. Surfactants have foaming ability and foam-stabilizing properties.

AAC block raw material ratio

The basic constituent materials of aerated block include calcareous materials and silicon materials. To meet the requirements of finished products, not only high-quality raw materials but also a good raw material ratio of AAC block are needed. Below is a typical formula for AAC blocks made from fly ash.

ComponentRatio (%)consumption per cubic meter (kg)
Fly ash70%350kg
cement13.8%25-30kg
Lime13.8%140-150kg
Phosphogypsum2.96%15kg
Aluminum powdertrace content0.4kg
aac block raw material ingredients ratio
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