There are many options on the market when it comes to choosing building materials. However, in recent years, autoclaved aerated concrete (AAC) has emerged as a popular choice for many construction projects. So what is autoclaved aerated concrete and why is it becoming more popular in the construction industry?
Autoclaved aerated concrete is a lightweight, durable, and energy-efficient building material made from natural raw materials such as sand, cement, lime, gypsum, and water.
One of the main advantages of aerated concrete is its lightweight. It weighs about one-fifth of conventional concrete and is easy to handle and transport. In addition, its excellent thermal insulation properties make it ideal for construction projects in areas with extreme weather conditions.
AAC has several other advantages such as high-strength properties, fire and pest resistance, and low maintenance requirements. Additionally, aerated concrete is a sustainable building material that helps reduce the carbon footprint of construction projects.
How Is Autoclaved Aerated Concrete Made
Raw materials used in AAC production
The manufacture of aerated concrete (AAC) involves the use of several raw materials such as sand, cement, lime, gypsum and water.
Sand is the main raw material used in the production of aerated concrete. It gives the material a lightweight, porous structure that helps reduce weight. Sand used for AAC production should be clean and free of clay, silt, and organic contaminants.
Add cement to the sand for added strength and durability. Ordinary Portland Cement (OPC) is the most commonly used cement in AAC production, accounting for approximately 10-15% of the total weight of the material.
Lime is added to the mixture to give the aerated concrete self-hardening properties. It reacts with aluminum powder to produce hydrogen gas, creating the porous structure of the material. Lime used in the production of aerated concrete must be free of impurities and have a high content of calcium oxide.
Gypsum is added to adjust the curing time of the mixture. It prevents the mass from curdling too quickly and ensures the proper consistency for pouring into molds.
Water is added to the mixture to promote the reaction between the aluminum powder and the lime, creating a gas that expands the mixture and creates its porous structure.
AAC manufacturing process: from mixing to curing
The manufacturing process of AAC involves several steps, including mixing, pouring, cutting, and autoclaving. The process typically begins with the preparation of the raw materials, which are then mixed in a large mixer to form a slurry.
The slurry is then poured into molds, where it is left to set and cure. Once the material has cured, it is removed from the molds and cut into the desired size and shape using a wire cutter.
After cutting, the AAC blocks or panels are placed in an autoclave, which is a large chamber that uses steam and high pressure to cure and strengthen the material. The autoclaving process typically takes around 8-12 hours, during which the material is exposed to temperatures of around 190-200 degrees Celsius and pressures of around 12-14 bars.
Autoclaving: what it is and how it affects the properties of AAC
Autoclaving is a crucial part of the manufacturing process of AAC. During the autoclaving process, the steam penetrates the pores of the material, causing the aluminum powder to react with the lime and produce hydrogen gas. This gas expands and creates the material’s porous structure, making it lightweight and insulating.
The high pressure and temperature of the autoclave also contribute to the material’s strength and durability. The pressure helps to compress the pores of the material, making it denser and stronger, while the high temperature promotes the curing process, making it even more durable.
Properties and Characteristics of AAC
Autoclaved aerated concrete (AAC) has several properties and characteristics that make it an excellent building material:
Lightweight: AAC is a lightweight material, with a density of around 500-600 kg/m³. This makes it easy to handle and transport, and it reduces the overall weight of the building, which can help to reduce the load on the foundation.
Thermal insulation: AAC has excellent thermal insulation properties, with a thermal conductivity of around 0.1-0.2 W/mK. This means that it can help to reduce heat loss and improve energy efficiency in buildings, which can lead to lower heating and cooling costs.
Fire resistance: AAC is a non-combustible material and has excellent fire resistance properties. It can withstand temperatures of up to 1,200 degrees Celsius for several hours without losing its structural integrity.
Sound insulation: AAC has good sound insulation properties, with a sound transmission class (STC) rating of around 44-45. This means that it can help to reduce noise transmission between rooms and buildings, which can improve the overall acoustic comfort.
Durability: AAC is a durable material that can withstand harsh weather conditions, such as freeze-thaw cycles, without losing its properties or structural integrity. It is also resistant to pests and rot, which can help to extend its lifespan.
Sustainability: AAC is a sustainable building material that is made from natural raw materials, such as sand, lime, and water. It has a low carbon footprint and can help to reduce the environmental impact of buildings.
Benefits of Using AAC
There are several benefits of using autoclaved aerated concrete (AAC) in construction projects.
Energy efficiency and sustainability: AAC is a highly energy-efficient building material that can help to reduce heating and cooling costs in buildings. It also has a low carbon footprint, as it is made from natural raw materials and does not require high energy inputs during production.
Cost-effectiveness: AAC is a cost-effective building material that can help to reduce the overall cost of construction projects. Although it may be slightly more expensive than traditional building materials such as bricks or concrete blocks, its lightweight and easy-to-handle properties can help to reduce labor and transportation costs.
Versatility: AAC can be used for a wide range of applications, including walls, floors, and roofs. Its versatility makes it a popular choice for builders and architects who want a flexible building material that can be adapted to different design requirements.
Improved indoor air quality and comfort: AAC has excellent thermal insulation and sound insulation properties, which can help to improve indoor air quality and comfort in buildings. Its low permeability also helps to prevent the growth of mold and mildew, which can lead to a healthier living environment.
Overall, the benefits of using AAC in construction projects are clear. It is a sustainable, cost-effective, versatile, and high-performance building material that can help to improve the energy efficiency, comfort, and durability of buildings.
Applications of AAC
Autoclaved aerated concrete (AAC) is widely used in residential and commercial construction projects, it is a popular choice for builders and architects who seek a flexible building material.
Walls: AAC is an excellent material for building walls due to its thermal insulation, fire resistance, and sound insulation properties. It can be used for both load-bearing and non-load-bearing walls.
Floors: AAC can also be used for flooring systems, as it has good load-bearing capacity and can provide excellent thermal and acoustic insulation.
Roofs: AAC can be used for roofing systems, as it is lightweight and has good thermal insulation properties. It can also help to reduce the overall weight of the building, which can be beneficial for the foundation and overall structural stability.
Many buildings around the world have been constructed with AAC, including residential houses, commercial buildings, and industrial structures. As more builders and architects become aware of the benefits of AAC, it is likely to become even more popular as a sustainable, cost-effective, and high-performance building material.
The future potential and possibilities for AAC in the construction industry are also significant. With advancements in manufacturing technology, the quality and performance of AAC are expected to improve, making it an even more attractive option for builders and architects looking for a versatile, durable, and eco-friendly building material.
In summary, AAC is a versatile and durable building material that offers a range of benefits, including improved energy efficiency, indoor air quality, and cost-effectiveness. Its potential for future growth in the construction industry is promising, and its many advantages make it a top choice for builders and architects worldwide.