Concrete is the best material for construction because of its strength and adaptability. However, there are variations within the concrete realm that are designed to meet particular needs and applications. Aerated concrete and foam concrete are the two most often discussed varieties; they differ in a few key ways.
Aerated concrete, also known as autoclaved aerated concrete or AAC, is a porous and lightweight building material. Its special mixture consists of sand, water, cement, lime, and a tiny bit of aluminum powder. A chemical reaction that occurs during production gives rise to hydrogen bubbles that spread throughout the mixture and form a cellular structure. This produces a material with outstanding thermal insulation qualities that is robust and lightweight at the same time. Because it is simple to handle and cut on-site, AAC is preferred for applications that involve both load bearing and non-load bearing components.
But the composition and production method of foam concrete, also referred to as aircrete or cellular concrete, are different. It is prepared by combining water, foam stabilizer, fly ash or Portland cement, a cementitious binder, and foam produced by a foaming agent. When the concrete hardens, the air bubbles created by the foaming agent give the mixture a cellular structure. Like aerated concrete, foam concrete is lightweight and has good insulation qualities. Because of its low density and capacity to form lightweight blocks and panels or fill voids, it is highly valued and suitable for applications where weight is an issue.
Although foam and aerated concrete both have the advantages of being insulating and lightweight, their manufacturing processes and intended uses are different. High-pressure steam is used in an autoclave during the controlled curing process of aerated concrete to help it reach its ultimate strength and durability. This process guarantees consistent product quality and uniform expansion. Conversely, foam concrete usually cures at room temperature and doesn’t need to be autoclaved. Its popularity in construction projects where quick installation is advantageous stems from its easier-to-use and more flexible production process for on-site applications.
The project requirements, such as structural requirements, thermal insulation requirements, and installation constraints, play a major role in determining which type of concrete to use: foam or aerated. Both materials have special benefits that address various facets of contemporary construction, ranging from residential structures to commercial complexes. Architects, engineers, and builders can choose the best material for their projects to achieve maximum performance and efficiency by being aware of these differences.
Features of production
The category of cellular concretes includes foam and aerated concretes. Although their preparation methods and compositions vary, the primary classification is based on the material’s strength and density grades (ranging from D300 to D1200), which are determined by the intended use:
- For thermal insulation works
- For thermal insulation and structural works
- For structural works
Note: The advantage of cellular concrete structural blocks over traditional building materials will only be in weight. The lower the thermal insulation index, the higher the density of the concrete. See the table below to find out more about the mechanical and physical specifications needed for each brand.
Apart from the composition, the final technical characteristics of the product are greatly influenced by the conditions in which the material hardens:
- Synthetic – hardening occurs in an autoclave unit, in a high-pressure environment and saturated steam (autoclave);
- Hydration – hardening occurs under natural conditions, or using electric heating and steam, but at normal pressure (non-autoclave).
Because the equipment is costly, large, and requires highly skilled personnel for maintenance, the first method is only utilized in factories. Because of the limited supply in the area, aerated concrete blocks made using this method are more expensive, and purchasing building materials from intermediaries results in a 30% price increase.
The hardening process is another distinction between foam concrete and aerated concrete; autoclave-made foam blocks are not available for purchase. Manufacturers primarily serve big clients, the developers, and are frequently uninterested in selling directly to local communities.
The second approach is significantly less complicated and costly. With the help of non-autoclave hardening, you can set up your own private production in the building site’s immediate vicinity or even in your own garage; all you need are the instructions.
But because of its ease of use, the market is overrun with inferior goods from dishonest vendors, and a gullible consumer frequently purchases something entirely unrelated to what he actually needed.
Table of mechanical and physical characteristics of autoclaved and non-autoclaved products for cellular concrete as per GOST 25485-89.
The table shows that different production methods for the same brand of blocks result in different strength classes for those blocks. Their resistance to frost varies as well. It turns out that autoclaved concrete is stronger than non-autoclaved concrete and has better qualities.
Aerated concrete
The filler and binder component are combined with plasticizers, surfactants, aluminum, alkaline additives, and water to create the material. An alkaline environment’s cements react with aluminum to release a gas (hydrogen), which causes the building mixture to foam and form a uniform porous filling.
Kindly take note! The primary distinction between foam concrete and aerated concrete is how the pores are formed—by employing foam or by releasing gas.
Subsequently, the confiscated blocks are extracted, cut, processed, and stored for a while. This is the process that yields what is known as an aerated concrete block. Their size, shape, and technical properties vary depending on whether they are used for structural or heat-insulating purposes.
Different hardening techniques and mixture compositions provide the necessary properties. You can learn more about the mechanisms that lead to pore formation in a gas block by watching the video included in this article.
Note: gas silicate is essentially the same as aerated concrete, with the exception that lime serves as the primary binder. Aerated concrete has pores created by the addition of aluminum powder, which releases gas when it reacts with alkalis. For this reason, aerated concrete and foam concrete are different in the same ways.
Additives to control structure formation, boost plastic strength, quicken hardening, and plasticize components might also be included in the mixture. Foam concrete can also receive some of these additions. It turns out that on this point, foam blocks and aerated concrete blocks are identical.
- The properties of sound and heat conductivity are directly dependent on the porosity of the material, and, therefore, a wall erected from blocks of a loose "spongy" structure will have good heat and sound insulation.
- Also, this material has greater strength among the group of lightweight concretes, and can be used for the construction of buildings up to 3 floors.
- Large dimensions of products and ease of working with them, allow you to save time and effort when constructing a structure. The mass of a typical D500 block with dimensions of 300x250x600 mm is no more than 30 kg. According to the listed advantages, there are practically no differences between foam concrete and aerated concrete.
- The porous structure and compositional features of aerated concrete are also its disadvantages. Moreover, such products do not work on bending at all, which is why the block becomes quite brittle.
- Its water absorption capacity is perhaps the strongest among cellular concretes – it can absorb water by almost 50% of its weight. And in a water-saturated state, all the declared advantages in terms of strength, frost resistance and permeability are lost.
- Also, aerated concrete blocks – especially those made in a non-autoclaved manner – have such an unpleasant property as shrinkage. The danger is that, with an unprofessional approach to masonry, the combination of all these disadvantages can lead to the formation of cracks in the building, and this reduces to zero all the savings when using this material.
- However, the consequences of cracking can be easily avoided by using high-quality blocks made by trusted manufacturers. It is necessary to build thicker walls, and do not forget about the encircling reinforcement of every 3-4 rows of masonry. And in small one-story buildings, such as a garage or a bathhouse, it is enough to simply rub the minor cracks that have formed with an adhesive mixture.
That is to say, extra steps, like plastering the facade and a high-quality foundation, are required to make up for all these drawbacks when building with aerated concrete blocks. But there is a construction technology for this, and if you follow it and follow the instructions exactly, there won’t be any issues.
Foam concrete
Foam concrete is a kind of cellular concrete in which the porosity is obtained by mixing pre-made foam into the cement mixture.
The following categories of products are produced using foam concrete:
- molded: partition (100x300x600) and wall (200x300x600);
- sawn – a large volume is subsequently sawn into blocks of a given size;
- poured or monolithic – used directly at the construction site, poured into removable or permanent formwork (for example, as insulation between layers of brick);
- reinforced – to increase the strength characteristics, basalt fiber, steel, etc. can be added to foam concrete., it is also called fiber-reinforced foam concrete.
Technical specifications of RS-Energo blocks manufactured in compliance with TU 5741-001-14059528-2004.
- bone glue;
- hide glue;
- pine rosin;
- caustic technical soda;
- scrubber paste, etc.
An illustration of a low-quality fiber foam block is seen in the photo. It breaks easily at the corners, is easily pierced, and can be easily rubbed into dust with your fingers.
Note: Every building material composed of cellular concrete needs to adhere to the specifications specified by the applicable GOST. That is to say, these specifications cannot conflict with the main GOST requirements, even if the manufacturer follows the Technical Conditions (TS) for products that he creates.
There is one clear benefit that non-autoclaved foam concrete has over autoclaved goods. It can be created right on the building site and applied in combination construction, such as when pouring monolithic thermal insulating concrete into formwork for permanent brick walls.
Comparative characteristics
The truth is that, at first glance, the answer to the question of how aerated concrete differs from foam concrete is fairly straightforward: composition. Building codes specify the properties of cellular concrete as a whole, meaning that foam concrete and aerated concrete can be made with the same strength and other parameters.
But after giving the question "what is the difference between aerated concrete and foam concrete" a thorough analysis, it became clear that foam blocks are only ever made by non-autoclave methods. However, autoclaving produces the majority of the aerated concrete blocks available for purchase. As previously mentioned, products that were autoclave-free hardened are lost during this separation.
It is important to remember that the autoclaved gas block and the non-reinforced non-autoclave foam block are the main objects of comparison when examining the comparative strength characteristics. Naturally, the foam block will lose in this situation.
However, fiber reinforcement and a non-autoclave method can also be used to produce gas blocks. The distinctions between foam blocks and aerated concrete blocks will be negligible in this instance.
The mechanical and physical properties of aerated concrete blocks that have not been autoclaved:
| Brand of products | D600 | D500 |
| Compressive strength class | B2 — B2.5 | B1.5 — B2 |
| Thermal conductivity coefficient, W/mºС | 0.13 -0.14 | 0.1 — 0.12 |
| Shrinkage, mm/m, no more than | 3.0 | 4.0 |
| Frost resistance | F 50 | F 50 |
| Vapor permeability, mg/m h Pa | 0.16 – 0.18 | 0.20 – 0.25 |
In addition, adding reinforcing fibers to foam concrete will increase its strength characteristics by at least 1.5 times. In tests, a block made in this manner has been shown to outperform autoclaved aerated concrete blocks (see the video in this article).
The cellular structure is another distinction between foam blocks and aerated concrete:
- Aerated concrete blocks the pores have the same diameter, and by hardening in an autoclave the filling is uniform across the cross-section of the block.
- And in foam concrete, hardening under natural conditions, firstly: there is a state when, under the action of gravity, light bubbles rise, and the porosity is accordingly distributed over the section from bottom to top. Secondly, the foam structure itself is not uniform, there may be bubbles of different sizes – this is clearly visible in the photo below.
It seems that there aren’t many differences between the technical properties of foam and aerated concrete building materials.
Broadly speaking, they are both:
- fire-resistant;
- ecologically safe;
- vapor-permeable (has a beneficial effect on the indoor microclimate);
- thermal insulation qualities during the operation of the building will reduce its heating costs.
Be aware that porous cellular concretes are extremely fragile. Structures built of these materials will also be susceptible to emergencies and vandalism, in addition to the challenges that may arise when hanging heavy equipment (special tools and fasteners are required). For instance, a car hitting a cellular concrete wall at a low speed may cause a large dent in this area. This means that it is important to take this into account when designing a construction site in order to ensure that the building’s walls are out of the way of oncoming traffic.
| Aerated Concrete | Foam Concrete |
| Uses cement, sand, lime, and water mixed with a foaming agent to create air bubbles. | Uses a cementitious paste mixed with foam to create air voids. |
Two common materials in the construction industry are foam concrete and aerated concrete, each with special qualities and advantages. In order to make wise decisions in construction projects, it is essential to comprehend their distinctions.
Aerated concrete is created by combining sand, cement, lime, gypsum, aluminum powder, and water. It is also known as autoclaved aerated concrete (AAC). The primary feature of AAC is its cellular structure, which is the result of a chemical reaction that releases hydrogen gas and distributes microscopic air pockets throughout the substance. As a result, a robust, lightweight building material with superior thermal insulation qualities is produced. Because of its reputation for strength and fire resistance, AAC is a great material for a variety of uses in both commercial and residential building.
Conversely, a cementitious slurry (cement, sand or fly ash, water) is combined with a foaming agent to create foam concrete. The foaming agent causes the mixture to bubble, increasing the concrete’s volume. In addition to being lightweight, foam concrete provides good acoustic and thermal insulation. It is frequently utilized in applications like void filling, trench reinstatement, and insulation layers where weight reduction is crucial. Although foam concrete tends to be less compressive than AAC, because of its flowable nature, it can be easier to work with in some situations.
The specific requirements of the project play a major role in determining which type of concrete to use: foam concrete or aerated concrete. While foam concrete offers versatility and ease of use in lightweight applications, aerated concrete excels in structural applications where strength and durability are crucial. Due to their ability to decrease material consumption overall and improve building energy efficiency, both materials support sustainable construction practices.
In summary, although aerated concrete and foam concrete have similar lightweight and insulating qualities, their manufacturing processes, structural features, and ideal uses are very different. Builders and architects can choose the best material to fulfill the performance specifications and project goals by being aware of these differences.
In exploring the differences between aerated concrete and foam concrete, it"s crucial to understand their distinct compositions and production methods. Aerated concrete, also known as autoclaved aerated concrete (AAC), is made by mixing fine aggregates with a binding agent and air bubbles generated by an aerating agent. On the other hand, foam concrete is created by blending a cementitious paste with a stable foam, typically generated mechanically or with the help of a foam generator. While both materials are lightweight and have good thermal insulation properties, aerated concrete tends to have higher strength and is often used in structural applications, whereas foam concrete is valued for its ease of production and ability to fill voids and gaps. Understanding these differences helps in choosing the right material for various construction needs, whether for load-bearing walls or insulation purposes.
