Aerated concrete

A very ecological and sustainable material


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MA Morocco

In development

About the project Edit

Aerated concrete is a building material used in big construction projects. Manufactured exclusively from natural raw materials, it is a skillful combination of water, sand, cement, aluminum power or paste, and air.

Aerated concrete is quite old. W. Michaelis created the process in 1880. Subsequently, E. Hoffmann came up with a second invention that expanded the mortars in 1889. Finally, Swiss Axel Eriksson started production and commercialization of the product in 1924 which is still being used today. Aerated concrete is used to build an estimated 500,000 single-family homes every year in Europe.


In what ways is this project unique and creative? Edit

The material has been used in northern European countries for a long time, but it’s slowly making its way to areas like France, for example, where interior home insulation is used. Interior insulation is less efficient because heat loss around the thermal bridges (joints where exterior walls or walls and floors meet) can represent up to a 40% energy loss in some buildings.

Aerated concrete is a material that is said to be self-insulating and doesn’t require any additional insulation material. It’s well-known for playing the dual roles of carrier and insulator which guarantees the insulation’s durability (making it impossible for rodents to weaken or damage insulation not attached).

Aerated concrete does not require additional insulation. Except when an exterior load-bearing wall is thicker than 20 cm, the monomur classification applies from 24 cm lambda 0.12. Millions of micro-cells of air in the honeycomb structure gives it its thermal insulating properties. Professionals call this type of insulation “self-insulating” or monomur. Uniformly trapped in the bulk of the material, the air insulates perfectly. There are materials with a density that can provide a coefficient of heat transmission (K-value) of 0.09 W/mK with a mechanical strength of 3Mpa, sufficient for building exterior load-bearing walls.

Aerated concrete ensures minimal heat loss. It keeps heat out in summer and keeps it warm in winter. It’s also a material sensitive to dampness like brick or agglomerate (prefabricated), therefore, the first row of a wall must be put on a level of mortar with either a waterproofing compound or weatherproofing strip. The first row of blocks must also be a minimum of 15 cm above ground. If not, there must absolutely be a sealant to protect the foot of the wall from water. It must, therefore, be maintained from any water penetration like all the other materials on the market (agglomerate, concrete, brick, etc.).

Blocks are generally white rectangular parallelepipeds. With a large selection of blocks, lintels, floor and roof slabs, and drywall tiles, an entire house can be built with aerated concrete. Construction using this material is very rapid and easy to work with at 3m2/hour for a complete wall 20 cm thick, thanks to assembly aided by adhesive mortars (meaning narrow-join fitting).

Density would be approximately 1 (1 block of 1 litre weighs about 1 kg).

What is the social value of this project? Edit

Aerated concrete is an ecological and durable material used in big construction projects. Made exclusively from natural raw materials, it is a clever combination of water, sand, cement CPJ 45 and millions of air bubbles with a swelling process for the mix.

In the winter, aerated concrete keeps cold air out and prevents heat from escaping. In summer, it keeps the heat out thereby maintaining fresh, cool air inside. This provides optimal thermal comfort and well-being.

What is the potential of this project to expand and develop? Edit

Its malleablitity, its easy workability and its bubbles

What was the triggering factor of this project? Edit

A swelling process that transforms a clever combination of natural raw materials into an efficient building material that is easy to work with makes aerated concrete an optimal thermal solution for any construction project. First commercialized in 1924, aerated concrete is made exclusively from natural raw materials – a clever combination of water, sand, cement CPJ 45 and millions of air bubbles with a swelling process for the mix.

In Europe, there are an estimated 500,000 homes built with aerated concrete. As well, it is used mainly in the construction of industrial buildings and firewalls. In Belgium, aerated concrete has been on the market since 1953. Energy Performance of Buildings (EPB) pose more installation problems like: thermal bridges, condensation and mould. Aerated concrete buildings respect the strictest of EPB standards. This means no more concerns for the architect or client who are guaranteed permanent results.

What is the business model of this project? Edit

Composition of materials to make aerated concrete:

. approximately 65% silica sand and quartz
. approximately 20% cement (CPJ 32.5)
. approximately 15% lime
. approximately 0.05% aluminum paste or powder
. approximately 1% gypsum
. water

About 5 m3 of finished product can be made with 1 m3 raw material; therefore, a block of 20% material and 80% air (valid for a block with a density of 400 kg/m³). 100% of the waste before autoclaving is recycled and afterward, more than 90% are put back into the manufacturing cycle.

Important phases in manufacturing are:

. preparing, measuring amounts and mixing of raw materials (sand, lime, cement, aluminum powder or paste, and water
. preparing the moulds
. pouring, rising and hardening of the paste
. cutting and shaping of products
. autoclaving with a pressure of about 10 bar at 180° C for 10 to 12 hours
. palettizing and plastic wrapping

Manufacturing with autoclave is an industrialization process that creates a mineral with an analogue molecular structure: tobermorite, calcium silicate hydrate. The process imitates this existing material in its natural state. The honeycomb structure is reproduced thanks to the aluminum powder that, along with other components during manufacturing, acts as an expansion agent.

This production method supports the running of closed-cycle plants. They do not emit liquid materials or solids that will pollute the water or soil, and the insignificant and inert waste issued during this phase of production is 90% recoverable. The only gas released into the air is water vapour.

Moreover, manufacturing aerated concrete uses little energy, part of which is indeed recycled for heating offices on manufacturing sites. Water required in the process can also be reused.

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