Compare claydite block and gas block

Starting construction, our readers often ask which is better: expanded clay or gas block, what are the differences and whether these popular building materials have similarities. Since childhood, we know that everything is known in comparison, therefore, how can one say what is better without making a comparative analysis, otherwise the conversation will be about nothing. We will not go into the intricacies of the production process, but simply put the subjects on different «scales».

Features of the composition of expanded clay block and gas block: similarities and differences

Speaking about the similarity of these two materials, it can be noted that both of them are used in construction, and they belong to the same group of materials — the so-called cellular concrete. Blocks based on expanded clay, like aerated blocks, are used for laying walls, but this is where the similarities end, with the exception of, perhaps, a few identical components in the composition of materials, and we will start with aerated concrete, which includes:

cement;

quartz sand;

gypsum, lime, slag, ash and other fillers;

aluminum powder (paste).

A logical question arises: why aluminum is introduced into the composition of aerated concrete blocks, and this is not difficult to explain. Aluminum, coming into contact with lime, slag, ash and other alkalis, releases hydrogen. The latter is essential for the formation of pores, and this is the main distinguishing feature of gas blocks. At the end of the process, the blocks can be cut, and this is not difficult to do, and then re-hardening occurs.

It is according to the variant of secondary hardening that aerated concrete blocks are divided into products of synthesis and hydration hardening. In the first case, hardening occurs in an autoclave, in the second — at atmospheric pressure or with the connection of special electric heaters. Gas blocks are divided according to the predominance of the main components into the following types:

calcareous, which include up to 50% lime;

cement with a content of 50% Portland cement;

slag, containing up to 50% mixture of slag, gypsum, lime or alkali;

ash, where up to 50% ash;

mixed containing different amounts of ingredients.

Having considered the composition and types of aerated concrete, you can proceed to a close acquaintance with expanded clay blocks. This is where the main differences between our test subjects begin. Unlike aerated concrete blocks, expanded clay blocks contain water, and expanded clay, or fired clay balls, is used as a filler. The main components are also cement and sand, and this is another similarity of materials.

The technical characteristics of the material depend on the number of individual ingredients that make up the composition. With a decrease in the amount of sand and cement, the specific gravity changes, which means that its properties also change, including strength, thermal conductivity and water resistance. In the composition of light mixtures, for example, sand may be completely absent.

Vapor barrier properties

Now let’s move on to a comparative analysis and draw the first conclusions. Experts, for example, dispelled the myth that the claydite block is similar in its properties to brick, because it includes the same cement mixture and clay. In fact, this is not entirely true, because in expanded clay concrete, cement plays the role of glue, connecting individual balls of clay. Looking ahead, let’s say that aerated concrete is better in this regard, now you will understand why. To do this, we consider the vapor barrier properties of both materials.

Expanded clay concrete

When the cement hardens in the expanded clay blocks, a waterproofing layer is created, which negatively affects the drying time of the material and its vapor barrier properties. Expanded clay concrete blocks have good vapor permeability, perfectly absorb moisture, but give water poorly, which contributes to the accumulation of condensate. Cement and sand pass steam well into the expanded clay granules, while water accumulates in them, but can no longer go outside.

aerated concrete

Consider a similar situation, but on the example of aerated concrete blocks. Aerated concrete has a porous structure, and its pores are open, so it is characterized by capillary activity, moreover, the structure of the material is more uniform over the entire surface. In our case, this means that the moisture accumulated in the form of condensate, under the action of capillary forces, moves to a dry surface, and, therefore, inside.

In expanded clay concrete blocks, waterlogging occurs, while in aerated concrete, moisture is distributed evenly. The fact that aerated concrete is better for laying walls outside the building can be seen by comparing the drying time of materials after the end of the winter period. Expanded clay concrete always dries inside the room, aerated concrete also dries inside, but if it is laid on top of the vapor barrier layer. In any case, it dries faster, because even with a vapor barrier, aerated concrete blocks have a moisture content of 8%, and the declared moisture content of expanded clay concrete is 10%, and these are only standard indicators, but in fact its moisture content is higher.

First conclusion! Expanded clay blocks dry for a very long time, and studies have shown that sometimes the warm season is not enough for complete drying of the material, while aerated concrete dries out in most cases by the onset of the next heating season.

Which material has the best breathability?

For comparison, I would also like to consider such an important indicator as breathability. Let us turn again to the structural features of the materials we have chosen for comparison. Expanded clay concrete has a high porosity, and the more irresponsible the manufacturer is in the manufacture of the material, the higher the porosity. With an increase in the pore size, the amount of cement used is reduced, the cost of the material becomes lower, but in this case there is no need to talk about any air permeability at all. Such blocks are blown by all winds, which cannot be said about aerated concrete, which is at least 20% waterproof.

Second conclusion: in order to make living inside expanded clay houses comfortable, you will have to additionally finish with a layer of plaster, both inside and outside the room. At the same time, in a house made of aerated concrete, it is enough to putty the walls with thin-layer plaster.

What should not be allowed when laying walls of expanded clay concrete

No matter what they say about poor performance in terms of airtightness, expanded clay concrete is widely used in construction, and especially low-rise. In an attempt to reduce the cost of construction, developers use blocks with round or square voids. The presence of such air pores increases the air permeability of an already not ideal material in this regard, which means that hollow claydite-concrete blocks are not the best option for laying external walls. In addition, the strength of the material is reduced.

Comparing other characteristics

When conducting a comparative analysis, we do not consider products from different manufacturers, as well as individual types of material, but take into account only average statistical data. The conditions of production and the attitude to the process of the manufacturer differ, but in general we can say that:

Expanded clay concrete has great strengththan aerated concrete, which has a high porosity compared to its competitor. Even hollow blocks based on expanded clay have the best strength characteristics, it is possible to talk about the same strength indicators of aerated concrete, but if we are talking about high-grade products, but in this case the cost of the material increases significantly.

By thermal insulation the properties of expanded clay concrete blocks are significantly inferior to aerated concrete.

crack resistance and other mechanical damage is also better for expanded clay concrete.

Aerated concrete is a bulk material, so the walls made of it are more fragile, so it is not advisable to attach heavy objects to them.

It makes no sense to compare materials on such an indicator as water absorption, since in this respect the subjects practically do not differ, although aerated concrete has a greater tendency to absorb moisture. In both cases, a waterproofing layer is required. As for the cost of the material, there are some subtleties here, which are also worth talking about.

Finishing Features

In order to understand which surface of which material is best suited for finishing, just look at the blocks with the naked eye. Aerated concrete has a smooth surface, therefore, it requires additional measures to increase adhesion. On the other hand, if the surface is ideally processed for finishing, it is enough to apply a thin layer of putty, and a thick layer of plaster has to be applied to expanded clay concrete.

What is more expensive?

No matter how “outstanding” characteristics this or that material possesses, when choosing, we most often proceed from our material capabilities. After examining the financial side of the issue, our experts came to interesting conclusions. It is believed that aerated concrete is more affordable, but this does not mean that this is the truth in the first instance. This issue requires careful study, but we did it for you. Draw your own conclusions, but it is reliably known that:

for the construction of a load-bearing wall, it is sufficient to use 20 cm blocks of expanded clay concrete, while aerated concrete of the same thickness is often not enough;

buildings made of expanded clay concrete blocks, due to the good strength of the material, do not require a device on top of the reinforced belt structure, and in the case of aerated concrete this is extremely necessary;

if it is necessary to lay concrete floors, then it is necessary to use expensive aerated concrete of increased strength, or ordinary porcelain stoneware, the cost of which is much lower.

Speaking about the cost of a particular material, one must take into account other associated costs, including delivery and installation. Wall insulation, for example, must be done in both cases, both with expanded clay concrete and aerated concrete blocks, although the latter are considered warmer, as mentioned above. Thus, it is not necessary to say that aerated concrete houses are cheaper. There is another advantage of aerated concrete — a lower specific gravity, and this simplifies installation and reduces the load on the foundation, on the construction of which you can also save.

In general, it all depends on the specific manufacturer and his responsibility, and in conclusion, I would like to say that expanded clay concrete has one indisputable advantage — it can be made at home. If you strictly follow the instructions during production and do not violate the technological process, you can save a significant amount on the material, and this is a big plus, given the constant increase in the cost of building materials.