AAC blocks (Autoclaved aerated concrete blocks) are made of cement, lime, slag, sand, fly ash, gas generating agent, air bubble stabilizer, and regulator as the main raw materials. They are porous concrete products manufactured through grinding, batching, mixing and pouring, gas expansion, pre-curing, cutting, autoclaving curing, and finished product processing in the AAC block plant.
It is mainly suitable for frame structure, pouring concrete external wall-filling, and internal wall partition, and can also be used for external walls or thermal insulation composite walls of multi-story buildings with anti-seismic ring beam structure. It can also be used for thermal insulation and heat insulation of building roofs. Compared with traditional clay bricks, autoclaved aerated concrete blocks can save land resources, improve the thermal insulation effect of building walls, and improve the energy-saving effect of buildings.
What raw materials are used in AAC block manufacturing?
Fly Ash: Fly ash is a by-product of coal combustion in thermal power plants. It is commonly used as a major raw material in AAC block production. Fly ash is rich in silica and alumina, which contribute to the strength and durability of AAC blocks.
Cement: Cement acts as a binder in AAC block production. Typically, OPC (Ordinary Portland Cement) or PPC (Portland Pozzolana Cement) is used. OPC is commonly preferred due to its higher strength, but PPC can also be used to achieve specific properties.
Lime: Lime is an essential component in AAC block production. It reacts with the silica and alumina present in fly ash to form calcium silicate hydrate (CSH), which provides strength to the blocks. Quicklime (calcium oxide) or hydrated lime (calcium hydroxide) can be used.
Gypsum: Gypsum is added to regulate the setting time of the AAC blocks. It helps control the rate of hydration of the cement, preventing rapid drying and cracking. Gypsum also enhances the workability of the mixture during casting.
Aluminum Powder: Aluminum powder is a key ingredient that creates gas bubbles in the AAC block mixture, leading to the formation of cellular structure and reducing the density of the blocks. The gas released by the reaction of aluminum powder with lime and cement creates pores within the material.
Water: Water is essential for the hydration of cement and lime, allowing the mixture to solidify and form the AAC blocks.
What is the Common AAC block raw material ratio?
It is very important to determine a good mix ratio to get finished products with good performance and meets the requirements of the building. Among many properties, the first is the bulk density and compressive strength, and the durability of the product must also be considered. The good ratio of AAC block can best suit the production conditions of the factory, such as pouring stability, fluidity of slurry, hardening time, and simple process flow.
The determination and use of the mix ratio of aerated concrete generally require the research and experiment of the theoretical mix ratio, the determination of the basic mix ratio for production, and the economy of the mix ratio. Moreover, the raw materials used are few in variety, widely sourced, and low in price, and industrial wastes are utilized as much as possible.
The ratio of raw materials used in AAC block production can vary depending on the manufacturer, desired properties, and local availability of raw materials. However, a commonly used ratio is as follows:
Fly Ash: 55-65%
Cement: 10-20%
Lime: 15-25%
Aluminum Powder: 0.05-0.08% (by weight of the total mix)
Gypsum: 2-3%
Water: Sufficient to achieve the desired consistency
It’s important to note that these ratios can vary, and manufacturers may adjust them based on their specific requirements, local regulations, and the desired properties of the final AAC blocks. It is recommended to consult with the AAC block plant or manufacturer for their specific raw material ratios.
Why the scientific ratio of AAC raw material is so important?
The scientific ratio of raw materials is the key guarantee for us to produce high-quality aerated block new building materials, and it also determines the performance factors such as the final aerated block equipment product strength. The basic constituent materials of aerated block equipment products include calcareous materials and silicon materials.
Under autoclaved curing conditions, the interaction between calcium oxide and silicon dioxide is the result of a hydrothermal synthesis reaction to produce new hydration products. Therefore, to obtain the necessary hydration products, the calcium-silicon ratio in the raw materials must be maintained at a certain ratio, so that it can fully and effectively react, to achieve the purpose of obtaining superior performance of the aerated block equipment products. We call this proportional relationship between calcium oxide and silicon dioxide in the raw material of the aerated block the calcium-silicon ratio of the aerated block.
Aerated block products are different from other silicate materials such as cement, and their interior also includes the shape and structure of pores, and good pores and structure depend on the gas expansion process of slurry. Therefore, a reasonable calcium-silicon ratio is very important.
