Types of cellular concrete: classification, characteristics and production features

Because of its special qualities and advantages, cellular concrete is a flexible building material that is becoming more and more well-liked. Cellular concrete is lighter and more insulating than traditional concrete because it has many tiny air pockets in it. Because of this, it’s a great option for a range of construction projects, including big commercial and residential buildings.

Cellular concrete comes in a variety of varieties, each with unique qualities and uses. Selecting the appropriate material for your project can be made easier if you are aware of these kinds and their unique advantages. Cellular concrete provides an answer for those seeking enhanced fire resistance, better thermal insulation, or a lightweight, workable material.

This article will examine the various categories of cellular concrete, going over their salient characteristics and manufacturing process. By the time it’s all through, you’ll know exactly what options are out there and how each kind can be used in construction.

What is the material

The primary characteristic that sets cellular concrete apart from other lightweight concrete is the presence of gas- or air-filled pores within its structure. This material comes in a wide range of varieties, which we shall now examine.

Classification

GOST 25485 89 cellular concrete stipulates the following characteristics and parameters that determine graduation:

The following types of binder are distinguished based on their type:

• Cement, containing cement in their composition in an amount of at least 50%.
• Lime. Consist of quicklime in an amount of up to 50% of the total mass. May also contain gypsum, cement or slag additives in amounts up to 15%.
• Mixed. Contains 15-50% cement, lime and slag.
• Ash, consisting of more than 50% evil.
• Slag, containing, respectively, slag in an amount of at least 50%.

Cellular concrete can be: Depending on the method of hardening

• Autoclaved
• Non-autoclaved.

In the first instance, the material is processed in a specialized apparatus called an autoclave, which exposes it to high temperatures and pressures in order to cause hardening. Synthetic hardening is another name for this kind of hardening.

In the second scenario, this process happens organically, under typical circumstances, or through electric heating. We refer to this process as hydration hardening.

The densities of cellular concrete can vary, which leads to variations in its range of applications.

Based on the aforementioned variables, there are

• Thermal insulating cellular concrete;
• Thermal insulation and structural;
• Structural.

Used only as insulation is thermal insulation. Less than 500 is its density, but it has an exceptional thermal conductivity coefficient. Because of its limited load-bearing capacity, which prevents it from supporting any weight other than its own relatively light weight, it is not utilized in wall construction.

The second iteration of cellular concrete has a numerical indicator that ranges from 500 to 900, indicating significantly greater durability. It is employed in the building of dividers and walls. Naturally, as density increases, so does the material’s capacity to hold onto heat.

The longest-lasting concrete is structural cellular concrete. It can have a density of between 1000 and 1200 kg/m3. As is evident, there is also a high thermal conductivity coefficient. It is employed in the construction of load-bearing structural elements for buildings up to 12 meters in height.

Additionally, cellular concretes are classified into the following types based on the method of porization:

• Foam concretes and foam silicates;
• Aerated cellular concrete and aerated silicate;
• Aerated concretes and aerated silicates.

The creation of cellular concretes also employs additional, modified techniques in addition to the ones mentioned above.

Among them are:

• Combination of gas formation and the aerated method. As a result, foamed aerated concrete is obtained;
• Swelling of the mass in a vacuum by gas formation;
• Bubbling the mass with compressed air with subsequent pressure reduction.

Cellular concrete is differentiated based on the type of siliceous component based on:

• Natural sand;
• On ash;
• On other secondary siliceous industrial products.

Advantages and disadvantages

Like any material, cellular concrete has advantages and disadvantages.

Let’s start by examining the advantages:

1. One of the most significant qualities is the thermal conductivity indicator. The material has a fairly high ability to maintain temperature, which significantly increases its value. This fact is easily explained: the whole thing is in the structure of the material, the pores of which contain air, which is a heat insulator. This characteristic is combined with sufficient strength.

Consequently, the utilization of cellular concrete products in block form during construction will result in a significant reduction of insulation and future heating costs. The level of soundproofing is also very high.

1. The material is safe for the environment and humans. He does not emit harmful substances into the atmosphere.
2. Cell concrete products are easy to handle, which significantly increases the speed of construction, and makes it possible to build structures with your own hands. In addition, the material is relatively light, which, in turn, reduces the load on the foundation when erecting walls, using such blocks.
3. High seismic resistance of structures, built from this material.
4. Combination of strength, density and weight leaves behind many building materials.
5. The ability to vapor permeate allows buildings to “breathe”, built using cellular concrete. Thus, a favorable microclimate is established in the room.
6. Since the composition of cellular concrete is characterized by the presence of mineral components, the material does not rot or undergo other biological damage.
7. The durability of cellular concrete is high. According to the manufacturers, a house built from this material will last at least 50-60 years.

Cellular concrete has drawbacks in addition to its many benefits. Its application presents certain challenges, and the substance is not truly universal.

Let us remember once more that cellular concrete is a porous substance. There are benefits and drawbacks to this fact.

The products’ high capacity to absorb water is the main selling point. In colder months, moisture that has accumulated can crystallize and destroy the cellular concrete product’s structure beyond repair. Accordingly, these kinds of constructions need to be finished both inside and outside with precision.

Cellular concrete products are brittle. This typically shows up when traveling or working, when mechanical impacts are most likely to occur.

These drawbacks, though, are entirely solvable. In the first instance, through properly built masonry, finishing, and material selection; in the second, through cautious handling.

Kindly take note! When using cellular concrete, extra caution and attention are needed. The majority of cellular concrete defects that surfaced in completed buildings belong to the same category and are caused by inappropriate use, poor masonry, a lack of reinforcement, or poor finishing.

Types of products made of cellular concrete

Cellular concrete products come in a variety of forms. They are widely employed in the building sector not only in Russia but also in other far-off and nearby nations.

Every year, the market for foam concrete and cellular aerated concrete expands, providing customers with an ever-greater selection of goods. Now let’s look at the options available to developers for products made with this material.

List of materials

Cellular concrete is used to make the following products:

1. Floor slabs, roof slabs;
2. Large-sized reinforced and unreinforced blocks;
3. Small wall blocks;
4. Small thermal insulation products;
5. Sound-absorbing products;
6. Interior partitions;
7. Wall panels;
8. Tray and bar lintels;
9. Heat-insulating backfill.

The following products are made with monolithic cellular concrete, which has the ability to solidify naturally at the construction site:

1. Bases for underfloor heating;
2. Multilayer and single-layer enclosing structures of buildings;
3. Heat-insulating layers of combined roofs.

I want to draw special attention to cellular concrete that is heat-resistant. Heating units must be used when operating and building. Fuel and material savings are substantial as a result.

Additionally, it ensures that the building (and/or unit) is protected from high temperatures, helps to create monolithic structures with increased thermal insulation capacity, creates comfortable working conditions for workers in the hot shop, and much more.

Cellular concrete blocks: comparative characteristics and scope of application

Blocks are the most widely used cellular concrete products in building construction. Aerated concrete and foam concrete are the two primary varieties. The method of pore formation and the production process itself are where they diverge most from one another.

• Cellular foam concrete is produced using a special foaming agent. A solution consisting of cement, sand and water is moved into the mixer, where a foaming agent is added. As a result, the latter gives porosity to the products.
• Cellular aerated concrete is produced without the use of the above foaming component. Porosity is achieved by a chemical reaction of lime and aluminum powder, which is used as a blowing agent.
• Both types of blocks are quite actively used in the construction of buildings; the GOST for cellular concrete is also the same for both types. However, the palm still belongs to aerated concrete.
• Let"s look at the main indicators of materials using the table and figure out why foam concrete is losing to its competitor.

Table 1: A comparison between aerated concrete and foam

Indicator name	Explanations
Installation speed	The construction of a building from both materials will occur quite quickly. Both aerated concrete and foam concrete blocks are relatively large in size, while their weight is small. Products are easy to process, they can be sawed, ground, given a special shape.
Appearance, precision of product geometry	Aerated concrete wins in this indicator. It looks more attractive and has precise geometry. But this can only be said about a block manufactured in a factory, that is, an autoclaved one.
Thermal conductivity	The difference in the thermal conductivity coefficient of these types of cellular concrete is very insignificant, but less durable foam concrete still comes out ahead.
Scope	Both materials have a wide range of applications. It depends, first of all, on the density of the block.

Cellular concrete is primarily utilized in the construction of walls and partitions, as well as for building insulation. It is also occasionally used to fill the frame of a reinforced concrete structure.

It’s also important to remember that the foaming agent, which needs to satisfy all quality requirements, directly affects the latter’s density. Certain manufacturers would rather cut costs.

As you can see, aerated concrete is in the lead, but foam concrete is still quite good. The cost and thermal conductivity advantages could make it a competitive product.

It’s also important to keep in mind that foam concrete is more prone to shrinking, even though this indicator follows the technical guidelines exactly.

Kindly take note! The pore structure of foam and aerated concrete also varies. They are open in the second instance, and closed in the first.

The adaptable and lightweight cellular concrete is well-known for its ability to insulate against heat. This article examines the various varieties of cellular concrete, going into detail about their classifications, distinctive qualities, and particular manufacturing processes. Every type of concrete, including foam concrete and autoclaved aerated concrete (AAC), has unique benefits that make it appropriate for a range of building uses. When selecting the ideal material for their projects, homeowners and builders can make more informed choices if they are aware of these distinctions.

Physical, mechanical, technical and other properties of products

Now, using the table, let’s examine the mechanical and physical characteristics of cellular concrete as determined by the technical requirements of GOST 25485 89.

Table 2 lists the mechanical and physical characteristics of cellular concrete.

Type of concrete, according to classification depending on density	Brand by density	Non-autoclaved concrete		Autoclaved concrete
		Frost resistance, cycles	Compressive strength, class	Frost resistance, cycles	Compressive strength, class
Heat-insulating cellular concrete	D300-D500	Not installed for heat-insulating cellular concrete	B0.5-B1	Not installed	B0.5-B1.5
Structural and heat-insulating	D500-D900	15-75	B1-B3.5	15-100	B1-B7.5
Structural	D1000-D1200	15-50	B5-B12.5	15-50	B7.5-B15

The table indicates that the mechanical and physical properties of autoclaved cellular concrete are better than those of non-autoclaved concrete. This can be attributed to the unique production technology.

Experts advise choosing cellular concretes with artificial hardening. They are more dependable and long-lasting, and a structure made of them will have the best performance qualities.

It is now worthwhile to examine the cellular concrete’s technical and physical indicators. According to GOST 25485-89, products must have the following numerical values.

Table 3. Indicators of the technical and physical characteristics of cellular concrete products:

Type of cellular concrete	Density grade	Thermal conductivity of concrete	Vapor permeability	Concrete moisture content in % sorption, at air humidity from 75-97%
Thermal insulation	D300-D500	0.08-0.1	0.18-0.26	8-18
Structural and thermal insulation	D500-D900	0.1-0.24	0.11-0.20	8-22
Structural	D1000-D1200	0.23-0.38	0.8-0.11	10-22

• According to these indicators, it becomes obvious that with an increase in density, the thermal conductivity of cellular concrete, as well as its vapor permeability and sorption moisture also change.
• It is worth noting separately the shrinkage indicators of cellular concrete. They also directly depend on the density and type of cellular concrete.
• Thus, for autoclaved aerated concrete with a density of 600-1200, made on the basis of sand, the numerical value of shrinkage should not exceed 0.5 mm/m2 of area.
• For products whose silica component differs from the above, the maximum value is 0.7 mm/m2.
• Non-autoclaved aerated concrete with a density of 600-1200 is allowed more – up to 3 mm / m2.

Please pay attention! The shrinkage of autoclaved (up to 400 density) or non-autoclaved (up to 500 density) aerated concrete is not specified by GOST.

First and foremost, shrinkage shows how resistant to cracks cellular concrete is. Of course, this directly impacts the material’s performance and durability; the higher the indicator, the more likely it is that cracks will develop on the surface.

The release humidity is another significant indicator that has been established by technical documentation.

Its value varies according to the siliceous component.

1. 25% for sand-based products;
2. 35% for ash-based products and other secondary industrial products.

According to GOST, which also outlines the fundamental acceptance criteria, all of the aforementioned properties are subject to control.

Production technology and material testing methods

The process of creating cellular concrete requires a lot of labor. Additionally, there is a unique technology for each kind that has an immediate impact on the qualities and attributes of subsequent products.

Features of production

As was already mentioned, different products are produced using different technologies, but the overall idea is the same. Let’s go over a few options step by step for clarity. Let’s begin by using the autoclave technique.

The steps in the process are as follows:

1. The ingredients are fed from the dispensers into the concrete mixer: first sand, then the missing water, the binder, additives in the form of gypsum and surfactants, and, lastly, the blowing agent. Aluminum powder is most often used.
2. To ensure the best reaction of the blowing agent and calcium hydroxide, the mixture of water and sludge is heated to 35%.
3. All components are thoroughly mixed.
4. Next, the mixture must be molded. There are 2 methods: injection molding and vibrocompression. In the first case, the gasification process occurs in a stationary form, using surfactants, changing the temperature and water content. In the second – on a vibration platform.
5. After the gas emission process is complete, excess mixture is removed, and the semi-finished product is cut to the desired size.
6. The next step is to process the blocks in an autoclave.

The non-autoclave approach differs slightly.

Foam concrete and non-autoclaved aerated concrete are made using very similar technologies:

• First, a solution is prepared by mixing all the components. Again, when producing aerated concrete, they mainly add aluminum powder, and when producing foam concrete – a foaming agent
• Then the solution is sent to the molds. Setting occurs after about a few days, after which the product is removed.
• The technical maturity of the block is then expected to be about 28 days. At the same time, foam concrete products need constant moistening every 6-8 hours in the first 7 days, and later every 10-12.
• If equipment is available, the blocks are steamed in specialized chambers at a temperature of 70-80 degrees and a pressure of up to 0.7 MPa. This significantly speeds up the hardening process.

A similar technology is applied in the production of monolithic aerated concrete. The mixture is immediately poured into the formwork or other structures at the construction site after it has been prepared.

The primary drawbacks are the potential for deviations from technical indicators and the absence of control over the solution when used independently. You can learn more about the processes used to create different kinds of cellular concrete by watching the video included in this article.

Testing

GOST specifies a set of testing procedures for cellular concrete products that are used to monitor the material’s quality at the output and ensure that it complies with the defined indicators. Let’s give it a closer look.

Table 4: Cellular concrete testing techniques

Direction of the method	Essence
Determination of shrinkage during drying	Consists in checking the change in the length of the tested samples when their humidity changes within 5-35% of the total mass of the product.
Frost resistance	The essence of the method lies in the alternate effect on the samples by freezing and defrosting them. The result of the test is an indicator indicating how many such cycles the product can withstand, while the compressive strength should not decrease by more than 15%, and the mass of the product – by more than 5%.

The frequency at which these tests are conducted has also been determined by GOST. Numerous indicators have cellular concrete passports on them.

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Type	Characteristics and Production Features
Aerated Concrete	Lightweight, good thermal insulation, made by adding aluminum powder to concrete mix, forming tiny air pockets.
Foam Concrete	Lightweight, good sound insulation, created by mixing a foaming agent into the concrete, forming uniform air bubbles.
Gas Concrete	High strength, fire-resistant, produced by introducing gas-forming agents like aluminum paste to the mixture, creating a porous structure.
Cellular Concrete	Lightweight, good insulating properties, made by adding air-entraining agents to create a cellular structure.

Because it is lightweight and has superior insulation qualities, cellular concrete is a highly adaptable building material. It is easier to choose the appropriate cellular concrete for a given construction project when one is aware of the various varieties available, such as autoclaved aerated concrete (AAC) and non-autoclaved aerated concrete (NAAC).

Because of its great strength and thermal efficiency, AAC is preferred for applications that require neither load bearing nor non-load bearing. Autoclaving is a process used in its production that improves its uniformity and durability. However, because NAAC doesn’t need to be autoclaved, it is more affordable and widely available, making it a useful option for a range of applications.

Understanding these materials’ properties and methods of production enables architects and builders to make well-informed choices that optimize the building process and guarantee the best results. Cellular concrete is still developing, providing creative answers to contemporary building problems.

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