- Composition of cellular concrete
- Manufacture of cellular concrete
- Properties of cellular concrete
- Respect the environment
Cellular concrete is a building material for structural work. It is said to "distributed insulation" and does not require the addition of any other complementary insulation material (reported insulation).
"Distributed insulation" is the famous 2 in 1: carrier and insulation, which guarantees the durability of the insulation (no weakening or possible deterioration by rodents in the absence of insulation reported).
Composition of cellular concrete
Made exclusively from natural raw materials, it results from a meticulous dosage of water, sand, cement, aluminum powder or aluminum paste, and air:
- About 64% siliceous quartz sand
- About 20% cement (cpj32.5)
- About 15% lime
- About 0.05% aluminum paste or powder
- About 1% of gypsum
- Some water
Manufacture of cellular concrete
When these different elements come into contact with metal molds, a chemical reaction occurs which causes hydrogen evolution. This results in a change in the volume of the dough (as a lift), a consequence of the formation of a multitude of tiny air bubbles. Thus, with 1 m³ of raw material (the dough), about 5 m³ of finished product is produced, ie a block composed of 20% of material and 80% of air (data for a density block of 400 kg / m³ ).
The important phases of manufacture are:
- preparation, dosing and mixing of raw materials (sand, lime, cement, powder or aluminum paste and water);
- the preparation of the molds;
- casting, lifting and hardening of the dough;
- cutting and profiling products;
- autoclaving under a pressure of about 10 bar and at 180° C for 10 to 12 hours;
- palletizing and plastic foaming.
The blocks are generally in the form of a rectangular parallelepiped of white color. A complete range consists of blocks, lintels, floor and roof slabs, partition tiles, etc. It allows to build a house entirely in cellular concrete.
The installation of the material proves extremely fast and easy to work: 3 m² / hour for a solid wall 20 cm thick thanks to an assembly made using a thin-set mortar.
Properties of cellular concrete
Cellular concrete does not require any additional insulation
• Except for a 20 cm thick bulk outer load bearing wall, this material is classified as "monomur" from any structure of this type that is 24 cm thick and 0.10 lambda. Its honeycomb structure consists of millions of micro-air cells, giving it its thermal insulation properties.
• Professionals call this type of insulation "distributed insulation" or "monomur".
• The air, uniformly trapped in the mass of the material, ensures excellent thermal insulation, making any reported insulation for the external walls superfluous (thickness 24 cm and +) superfluous.
• The cellular concrete is a hygrothermal regulator, ensuring the inhabitants, walls of interior walls warm in winter. More sensations of "cold wall". By cons in summer, because of its inertia, the material is an obstacle to external heat, which provides an appreciable comfort to those who live in houses built with this material.
• Because of its composition, aerated concrete is a material that breathes by allowing water vapor naturally released by occupants and their daily activities to migrate. This hygro-regulation is essential to fight the ambient humidity, to avoid the formation of condensation and thus, the appearance of molds. For this reason, it is important to use an interior finish, a plaster or plaster thin plaster rather than a plasterboard type BA13 which strongly inhibits this migration of water vapor.
This quality makes it sensitive to capillary rises like brick or agglo. It is therefore imperative that the laying of the blocks of the first row of wall is done on a base of a mortar waterproofed either in the mass, or by a band of waterproof arase (bituminous felt) taken between two layers of mortar.
Warning, because of the very low presence - 0,05% of the recipe - of aluminum in its composition, it is advisable to avoid putting it in contact with other metals (risk of stack effect being able to alter the concrete). For this reason the DTU 20.1. recommends the use of galvanized metal (lattice) or stainless steel (hardware) in a cellular concrete wall during chaining (HA steel, high adhesion) or other reinforcing operations.
Finally, it is an incombustible mineral material. Classified M0, the cellular concrete is nonflammable. It does not release any gas or toxic smoke. In the event of a fire, a wall has a fire-resistance capacity of 6 hours.
Respect the environment
This type of manufacturing favors the operation of plants in closed cycle: they do not reject any liquid or solid substance likely to pollute water or soil, and the waste resulting from this phase of production, small and completely inert, are valued at 90%. In the atmosphere, the only gas released is water vapor.
The manufacture of cellular concrete also requires little energy, part of which is also recycled to heat offices adjacent to production sites and the water needed for this process can also be reused. The result is the first quality of the cellular concrete block: its lightness which allows it a greater dimension for a smaller weight.
100% of the waste before autoclaving is recycled, and after autoclaving more than 90% is returned to the production cycle.
(photos / visuals: © Xella-Thermopierre, except special mention)
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