Aerated concrete: composition and properties of the material, production method, scope of application and popular manufacturers

Because of its special qualities and range of uses, aerated concrete has grown in popularity in the building sector. This material, which is well-known for being insulating and lightweight, has several advantages for both homeowners and builders. You will be able to appreciate why aerated concrete is unique in today’s construction when you are aware of its composition, manufacturing processes, and applications.

Cement, lime, sand, water, and a trace of aluminum powder are the main ingredients of aerated concrete. The material’s distinctive lightness and insulating qualities are caused by the reaction between the aluminum powder and the other ingredients, which produces tiny air bubbles throughout the mixture. This procedure produces a very effective building material that can lower construction costs and increase energy efficiency.

Aerated concrete is made by combining the ingredients and then pouring the mixture into molds. As a result of the chemical reaction, the mixture solidifies and expands. After it solidifies, it is divided into different-sized panels or blocks. The final product is strengthened and preserved by curing it in an autoclave, a steam chamber with high pressure.

Aerated concrete can be used in a variety of ways due to its adaptability. It is frequently used for walls, floors, and roofs in residential, commercial, and industrial construction. Because of its light weight, the structure is subjected to less overall load, and its thermal insulation qualities help save energy. Aerated concrete is a popular option for many construction projects since it is also highly sound-insulating and fire-resistant.

Numerous producers are experts in creating premium aerated concrete goods. Among the most respectable businesses on the market are H+H, Aercon, and Ytong. These producers are renowned for their cutting-edge manufacturing processes and dedication to sustainability, guaranteeing that aerated concrete will always be a dependable and environmentally beneficial building material.

Porous (cellular) concrete – what it is

Cellular concretes are classified as particularly light compositions because of their large number of air pores in their structure.

Materials are separated into two categories based on the method of porization: foam concrete, which is created by thoroughly mixing the composition with foam that has already been prepared, and aerated concrete, which is created by adding gas-forming additives to solutions.

The most common binder materials are lime-siliceous materials, gypsum, and Portland cement. Concrete can be allowed to naturally harden or can be treated with heat and moisture, high temperatures, and high pressure in autoclave units.

High levels of thermal insulation, vapor permeability, resistance to biological influences, and durability are characteristics of the materials.

Cement, lime, sand, water, and an expanding agent are the ingredients of aerated concrete, a lightweight and adaptable building material. It is perfect for a variety of construction projects because of its special qualities, which include high thermal insulation, sound absorption, and fire resistance. In order to create a porous structure, the ingredients are mixed and air bubbles are introduced. The porous structure is then cured and cut into blocks or panels. Buildings for residential, commercial, and industrial use this material extensively. Prominent producers such as Ytong, H+H, and Aercon provide a selection of aerated concrete solutions to meet various construction requirements.

Advantages and disadvantages of the material

Items composed of porous composites are ideal for the circumstances of contemporary building construction:

1. Frost resistance of the material allows the use of wall blocks made of cellular concrete in any climatic conditions.
2. High mechanical and thermal properties (density 300-1200 kg/m³).
3. Vapor permeability.
4. Resistance to chemical influences.
5. The autoclave production method involves the use of environmentally friendly raw materials.
6. Concrete blocks are easy to cut with both electromechanical and manual tools.
7. Use of domestic equipment and production technology allows us to manufacture products 1.5-2 times cheaper than imported analogues.
8. Thermal insulation products are several times stronger than mineral wool slabs and are in no way inferior to them in terms of performance characteristics.
9. Buildings made of porous concrete are durable. The material does not rot, does not burn and is not damaged by rodents and insects.

1. Sharp changes in air temperature and increased humidity cause structural deformations in the material.
2. Low resistance to tensile stresses leads to the formation of small cracks on the surface of the walls.
3. The material does not withstand impact effects. For example, a solid expanded clay concrete block easily crumbles and splits even when dropped from a small height.
4. Monolithic concrete is not recommended for the construction of foundations.

Composition and structure

A carefully chosen mixture of a binder component, finely ground siliceous filler, water, and a foaming agent produces cellular concretes.

Portland cements with aluminate content of alitic form a binder for the creation of porous concretes that solidify under typical circumstances.

Lime, pozzolanic cement, slag Portland cement, and other binders are combined to create solutions that get stronger in autoclaves.

Dolomites, fly ash, marshalite, and ground quartz sand can all be utilized as siliceous components.

Sometimes, cellular concrete’s composition is enhanced with a significant filler:

• slag pumice;
• vermiculite;
• perlite;
• expanded clay, etc.

Foam is prepared using glue-rosin, aluminosulfonaphthene, and resin-saponin additives. Aluminum powder is added to the aqueous solution, which causes gas formation in concrete.

The micro- and macrostructure of cellular concrete is determined by the percentage ratio of the material components.

A significant amount of cellular pores (85–92%) and interpore partitions serve as indicators of the macrostructure. Helium, contraction, and capillary cells make up the microstructure. The primary technical characteristics of products are determined by the amount and type of porosity as well as the ratios of siliceous components.

Types and properties of the material

The process used to create the cellular structure and the kind of binder component are used to categorize porous concrete.

Cement and cementless varieties of autoclaved cellular concrete are available:

• cement – aerated concrete, foam concrete;
• lime – gas silicate, foam silicate;
• magnesia binder – gas magnesite, foam magnesite;
• gypsum base – gas gypsum, foam gypsum.

The specific gravity of the concrete, the type of silica filler, the binder’s mineralogical composition, and the autoclave heat treatment conditions all affect a material’s mechanical and physical properties.

By density and thermal conductivity

The primary goal of designing porous concrete is to achieve the material’s ideal density while using the least amount of blowing agent and binder possible. Little oval-shaped cells should make up the structures’ structure.

Initially, the gas-forming capacity and volume of the additives determine the density. The volume of silica filler and the ratio of water to binder weight (W/T) have some bearing on the quality of the concrete. A higher W/T increases the mixture’s fluidity.

Consequently, the ideal circumstances are created for the solution’s porous structure to form. The material’s density increases with decreasing cell size.

Building structures’ thermal conductivity is decreased by concrete’s high density. Materials with high porosity and low thermal conductivity have better thermal insulation qualities.

By hardening method

Cellular concretes are classified as either natural or autoclave dried products based on the strength gain method. In autoclaves, hardening takes place in an environment saturated with water vapor at a temperature of 170–20 °C and an excess pressure of 0.9–1.3 MPa.

The linear shrinkage for non-autoclave hardened concretes is up to 3.5 mm/m. Regarding autoclaved: 0.3–0.8 mm/m.

Additionally, heat-treated concrete has strength that is 8–10 times greater than that of naturally hardened materials.

Strength characteristics

The type of porosity in the material structure and the interpore shells’ adhesion force determine strength. The variation coefficients of concrete determine its tensile-compressive strength. For cellular materials, the average index values shouldn’t go above 15%.

Reducing W/T and using vibration technologies during mixture preparation and swelling are two ways to improve strength characteristics. Concrete’s strength is increased and the water-solid ratio is lowered when vibrations in the cement paste increase its plasticity and mobility.

Adding fibers to the mixture is another way to boost its strength. You can obtain products with a strength of more than 70 kg/cm² using this method.

Water absorption and frost resistance

The sort of binder ingredient used determines how well porous materials absorb water. This corresponds to 35–45% of the substance’s volume in silicate concretes and 40–45% in cement concretes. It is advised to use products with these specifications only indoors, where the air humidity is not higher than 50%.

Modifying additives are used to increase a material’s resistance to moisture. Hydrophobic coatings serve as protection for operational structures. External structures should operate with a standard operating humidity of 5%.

Concrete’s ability to withstand frost is dependent on how much water it absorbs; with appropriate precautions, this absorption can reach 25–100 cycles.

Accuracy of geometric dimensions

A minimum amount of error in the geometric dimensions of products could be achieved by employing contemporary equipment and modernizing production technology. Because the wall blocks are straight, adhesives can be used in place of cement-sand mortar. With this method, the masonry speed has increased by nearly two times while the labor intensity of the work has decreased.

Shrinkage

Concrete shrinkage deformations result from the hardening process; these deformations reduce the structure and mixture volume. It has been determined that autoclaved concrete shrinks intensely for 60 days before stopping at relative humidity levels between 60 and 80% and temperatures as high as 20 °C.

The heat treatment’s technical parameters have an impact on the size of deformations. Concrete shrinks less when the heating temperature is higher.

By adding 15–30% of fillers (such as expanded clay, blast furnace slag, etc.) to the mixtures, swelling and compression of the cellular materials’ structure can be minimized.

Production Methodology

Lime, cement, sand, and water are commonly utilized locally to make cellular concrete. The mixture is slightly mixed with gas-forming additives to encourage the formation of air cells in the viscous mass.

The composite is then molded and put in an autoclave to finish the hardening process. Through-passage and dead-end installations with a diameter of 2.5–2.8 m are used for hydrothermal treatment. There are no byproducts from the technologies utilized that contaminate the land, air, or water.

Aerated concrete

The ingredients of a concrete mixer are cement, lime, and coarse-grained sand. After adding warm water, the ingredients are combined and stirred for five minutes. The mixture is then continued to be prepared by adding an aqueous solution of aluminum powder to the tank.

The chemical reaction produces hydrogen bubbles in the mixture, which lead to the appearance of many pores and capillaries in the concrete structure. The completed mixture is poured into forms that have been prepared.

Aerated concrete blocks are sent to an autoclave unit after they have reached a preliminary strength. Here, high temperatures are used to cause the products to finally harden.

Foam concrete

A concrete mixer is started and filled with sand, cement, and water. The foam generator is filled with dry concentrate for foam preparation. Addition of warm water is made. Stir according to the directions on the back of the package until a uniform viscous mass is achieved.

After five minutes of waiting, the completed solution is added to the concrete mixer. The composition is then poured into the molds following this. For a period of 30 to 60 days, they are kept in a room with good ventilation so that the concrete can strengthen.

Gas foam technology

Air entrainment during foaming and swelling during gas emission are the two processes that are combined in the gas foam method of making cellular concrete.

Components that work well together must be chosen in order to create a shrink-free material with a consistent porous structure. Additives that produce gas and form foam are loaded simultaneously. The gas generator activates and stops the development of deformation at the exact moment when the foam can shrink.

They are parallel to crystallization processes because of the smoothly dosed gas emission of the reaction of the formation of a cellular structure. The solution’s structure is not affected by the formation of new gas bubbles; rather, they simply compact the interpore partitions and move the binder’s grains into the foam’s newly formed pores.

Application areas

A variety of reinforced concrete structures are made possible by the production of products from cellular concrete:

• wall panels;
• reinforced concrete floor slabs;
• bar and tray lintels;
• hollow brick;
• thermal insulation materials;
• warm ceramics (porous ceramic block);
• masonry blocks.

Aerated concrete blocks and foam concrete are the most popular choices for individual construction. A home’s exterior wall composed of porous materials can support a considerable amount of weight. Buildings of any shape and for any number of uses are possible thanks to the material’s dimensions and strength qualities.

When it becomes necessary to add stories to a structure without reinforcing the foundations already in place, light concrete is also utilized in the reconstruction process.

Categories of products

The properties of thermal insulation and density vary amongst porous concrete.

These qualities allow them to be categorized into three groups:

• thermal insulation materials;
• thermal insulation and structural;
• structural.

Typically, D300–D500 concrete density is only utilized as a heater. Walls and partitions cannot be installed using these products because of their low standard operating load.

The primary building material used to construct both internal and external structures is the D600–D900 density block. They are intended for use in the construction of three-story residential and public buildings.

The properties of structural porous concrete D1000–D1200 have the highest strength. It is extensively employed in the manufacturing of roof slabs, masonry and foundation blocks, precast concrete, etc.

Application

The following construction domains use cellular concrete:

1. Monolithic housing construction.
2. Production of individual structural and decorative products.
3. Thermal insulation of utility networks, roofs and external walls of buildings.

In addition to being used in construction, manure and crushed porous concrete fertilize the soil. The material is used as warm bedding for cattle on livestock farms.

Topic	Details
Composition	Aerated concrete is made from a mixture of cement, lime, sand, water, and an expansion agent like aluminum powder, which creates tiny air pockets.
Properties	Lightweight, good thermal insulation, soundproofing, fire-resistant, and easy to cut and shape.
Production Method	The mixture is poured into molds, allowed to rise and set, then cut into blocks or panels before being cured in a steam chamber.
Scope of Application	Used in residential, commercial, and industrial construction for walls, floors, and roofs.
Popular Manufacturers	Ytong, Hebel, and Aercon are well-known producers of aerated concrete products.

Aerated concrete’s remarkable blend of strength and light weight has made it a popular choice in construction. Tiny air pockets are created within the material by its composition, which mainly consists of cement, lime, water, and an expanding agent like aluminum powder. The concrete’s weight is greatly decreased by these air pockets without sacrificing its structural integrity.

These components are combined, the air bubbles are produced by a chemical reaction, and the mixture is then cured in an autoclave to produce aerated concrete. This procedure makes the material stronger and more insulating, which makes it a great choice for buildings that use less energy.

Aerated concrete’s versatility is demonstrated by the variety of uses for it. It is frequently used to build roofs, floors, and walls for both residential and commercial structures. It is the best material to use for safe and environmentally friendly building projects because of its fire resistance, sound insulation, and thermal insulation capabilities.

High-quality aerated concrete is produced by a number of well-known manufacturers, such as Ytong, H+H, and Aercon. These businesses are well-known for their dedication to quality and innovation, offering dependable building materials to contractors worldwide.

All things considered, aerated concrete provides a special set of advantages that make it an important component of contemporary building. Its strength, insulation capabilities, and lightweight design guarantee that it will always be a well-liked option for a variety of construction projects. Aerated concrete is a wise, environmentally friendly choice for building sturdy commercial buildings or improving the energy efficiency of residential buildings.

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