Facing aerated concrete: methods and their features. brick

Aerated concrete is a relatively young building material, which belongs to structural and heat-insulating products and allows to increase the energy efficiency of the bearing and enclosing structures. However, the physicochemical properties of the material require its protection from exposure to the external environment, and we want to tell you what to veneer a house of aerated concrete.

Facing technology for aerated concrete

Aerated concrete and its properties

Газобетон – своеобразный материал, имеющий множество преимуществ и положительных качеств, однако, существуют также и некоторые условия его эксплуатации, невыполнение которых может привести к потере всех достоинств, ради которых были использованы блоки. Чтобы ни у кого не возникало сомнений по этому поводу, мы сначала рассмотрим свойства и особенности этого материала, на основе которых покажем необходимость тех или иных конструкционных решений (см.также статью «Армирование элементов монолитных железобетонных зданий: основы»).

So, we have an artificial material made from quartz sand, cement, a blowing agent and additives in the form of lime, gypsum, slag and ashes. The production process looks like this: an aluminum paste or emulsion is added to the cement-sand mixture, which reacts with calcium hydroxide in the solution to form hydrogen and calcium aluminate.

The released hydrogen foams the solution, and it expands in volume like a dough, filling the mold. As a result, we get a porous material with a huge number of cells with a size of 1 - 3 mm, resembling stone foam. The cement mortar sets and the block acquires primary strength.

Then the blocks are subjected to autoclave or non-autoclave treatment, where they give them the final hardness and stability. The strength characteristics of aerated concrete is significantly inferior to traditional concrete or brick, but can be used for the construction of load-bearing walls in low-rise construction and for the construction of enclosing structures in buildings with unlimited height.

The basic physical properties determine the advantages and disadvantages of this material:

• The blocks have a density of 300 to 800 kg / cu. m., which is several times less than that of brick, stone and concrete. Consequently, the weight of a building built of aerated concrete blocks will be several times smaller, which means that one of the most expensive structures - the foundation - will become several times cheaper;
• The thermal conductivity of cellular concrete is several times lower than that of a brick, and in aerated concrete it is comparable to the thermal conductivity of wood. At the same time, the technology of laying blocks and the thickness of the walls make the energy efficiency of the walls of such blocks higher than that of log walls or walls of glued laminated timber;
• The compressive strength of a material makes it possible to call some of its varieties as structural materials, most often structurally heat-insulating, and sometimes purely heat-insulating. Nevertheless, this strength is quite enough for the construction of three-story buildings;
• The structural strength of the blocks allows you to easily cut them with hacksaws, hammer nails and anchors, drill and drill with tools without carbide tacks. Diamond drilling of holes in concrete or cutting of reinforced concrete with diamond circles is useless here, and therefore gas concrete can be called cheap and easy to work, comparable to wood in this indicator;
• The porous structure makes the material extremely hygroscopic, its ability to absorb moisture can be compared with a sponge. This is one of the main drawbacks that require mandatory measures to prevent the contact of the surface of the blocks with water and water vapor;
• Aerated concrete perfectly passes steam and other gases, which makes it preferable to many other materials, as it is able to maintain intensive gas exchange with the environment and naturally regulate the humidity inside the room, which is very important from the point of view of health and comfort of the residents of this room;
• The material contains a large amount of alkaline salts - calcium aluminates, which, when in contact with the acidic environment characteristic of street sediments mixed with dust, unevenly darken and spoil the appearance of the walls.

Note! As we have shown, aerated concrete has many advantages, which are preserved provided that its surface is protected from moisture. In other words, the outer surface of the block requires a mandatory lining.

However, this is not the whole truth. The fact is that the hygroscopicity of the material is so high that it can be saturated with moisture from the interior. As a result, its density will increase, the insulating qualities will fall, and corrosion processes will begin inside the material.

Note! To prevent this from happening, gas must be provided to the external surface with outside air, or, in other words, to ventilate the facade.

That is why the facing of aerated concrete walls with impermeable materials is undesirable, including film-forming paints, foam plastic, non-ventilated plastic panels, cement-sand plaster (due to incompatibility with cellular blocks), brick without ventilation gap.

There is a technology for cladding such facades with clinker tiles with mortar joints with a vapor-permeable mixture, however, such vapor-permeability may be insufficient, and therefore the technology is considered dubious and controversial.

Ways of facing

Как мы показали, облицовка ячеистого бетона – обязательная и необходимая мера. Более того, такая облицовка должна удовлетворять требования газообмена, а значит иметь сравнимую с газобетоном паропроницаемость или вентиляционный зазор (читайте также статью «Фигуры из бетона: советы по изготовлению»).

These requirements correspond to several types of facade systems:

• Ventilated outboard facade structures, such as siding, wall paneling, blockhouse, and the like. They are one of the most acceptable solutions in terms of price / reliability and are used quite often;
• Special thin-layer plasters for cellular materials. They are distinguished by the ability to retain moisture during the hardening process and therefore are suitable for finishing this type of blocks. Applied in the traditional way using reinforcing mesh followed by grouting;
• Brick Cladding с обязательным вентиляционным зазором. Крепление облицовочного кирпича к газобетону осуществляется с помощью гибких связей с использованием анкеров, гвоздей, арматуры, пластин и т.п.;
• Coloring special vapor-permeable formulations. This method seems to be the least reliable from the point of view of protecting the blocks from the external environment, especially in the Russian climate.

Note! Thermal insulation of the facades of cellular materials should be vapor-permeable materials. The most commonly used plates of basalt fibers or mineral wool, and materials such as penofol or polystyrene foam will be inappropriate here.

Due to the low structural strength, the mounting of brackets for mounted structures is carried out with increased care on special expanding dowels, and the depth of laying of anchors and plates for fixing bricks should be at least 100 mm.

Brick Cladding

Taking into account the peculiarities of the climate and temperature regimes of our latitudes, we recommend to revet the facade with a brick.

For those who plan to do it themselves, we have compiled a thesis instruction:

1. At the stage of laying the foundation, it should be noted that the thickness of the walls will be equal to the thickness of the masonry of blocks plus a gap of 30-50 mm plus masonry in one or half of the brick. The overhang of the brick from the base should not exceed 30 mm;

1. At the stage of the construction of load-bearing walls, you can bookmark flexible links.. If these are plates, they are nailed to a horizontal surface and taken out, then bricked between bricks. In addition, you can hammer an anchor in the process of laying a facing wall with a 600 mm pitch horizontally and a distance of 500 mm between the rows (or three or four rows of bricks);

1. If you plan to warm the facade, you should consider the thickness of the insulation when calculating the thickness of the walls. In addition, you should leave a gap between the insulation and lining of at least 30 mm and cover the plates with a windproof membrane. Insulation must be vapor permeable;

1. In the brickwork, the products are left below and above with a total area of ​​at least 1% of the cladding area for proper ventilation of the walls.;

1. Spiral nails can also be used for a bundle of walls, which are hammered into the wall at the level of the masonry joint and brickled into the wall. The most acceptable from the point of view of heat engineering are connections made of fiberglass reinforcement, which are driven into drilled holes of smaller diameter and also embedded;

1. Use steel elements for connections is not worth it, as they quickly rot under the action of corrosion. Also caution should be used galvanized plates, it is better to use stainless steel or plastic parts;

1. For lining, use only high-quality facing bricks, ceramic or silicate.. Otherwise, costly and time-consuming stucco facade, or other exterior finish, which will hide the disadvantages of red brick.

  Note! It is better to perform work on external cladding in warm, dry weather. Work at low temperatures or during rain is undesirable.

Conclusion

Газобетонные блоки – превосходный строительный материал, который при правильном подходе и соблюдении технологии способен служить сотни лет, сохраняя тепло и уют в вашем доме (см.также статью «Бетонирование двора: советы новичку»).

Facing of blocks is carried out taking into account some rules which are considered and visually shown in video in this article.