The art and science of making Hebel AAC panels

The question often arises ‘how can a Hebel AAC panel be strong and solid yet lightweight for its size?’ The answer lies in the manufacturing process where CSR Hebel sits amongst the best in the world.

We won’t tell you our secrets but this snapshot of how CSR makes Hebel panels in Australia will give you an insight into why they are such a remarkable building material. Hebel panels reduce heating and cooling loads on buildings, are non-combustible, can be produced to the size needed, are easily cut, make construction fast and efficient and are a better choice for the environment compared with concrete or brick veneer.

Creating the best corrosion protected steel reinforcement

There are two parts to making Hebel panels that come together during the manufacturing process. One is the production of corrosion protected steel reinforcement and the other is the making of the Hebel AAC. Let’s begin with the steel reinforcement, also called mesh, that’s processed at the CSR Hebel facility in Somersby NSW.

The reinforcement manufactured into Hebel AAC panels isn’t just any steel. It goes through a rigid process at the Somersby facility to ensure high quality steel is sourced and the best corrosion protection methods are used.

Once the steel reinforcement is coated with corrosion protection it’s configured to suit a particular Hebel panel product batch. For instance Hebel PowerPanel with a tongue and groove profile can be ordered in either single mesh or double mesh (called caged), in a range of sizes and custom orders. And the Hebel product offering is extensive, requiring innovative ways of maximising efficiency in production so the two parts of manufacturing meet seamlessly. That means the configured steel reinforcement is placed in a mould ready for the slurry pour at the right time. The reasons why timing is critical – especially in the chemical reaction stages – are explained in the next section.

Corrosion protecting steel reinforcement for Hebel panels.

Preparing steel reinforcement for placement in an AAC mould.

The making of the Hebel AAC cake

Hebel AAC is produced in a similar way to making a cake that only the best cook can deliver. Water and dry ingredients – sand, lime and cement – are mixed with an expansion agent to form a semi-liquid mix called slurry which is poured into a mould. Chemical reactions occur between the ingredients causing hydrogen to form, which in turn causes the slurry to rise. This is called the pre-curing stage and is a precise science fine-tuned by CSR. The hydrogen gas then dissipates leaving extremely small, finely dispersed air spaces. This is the essence of why AAC is 80% lighter than concrete, yet strong and solid with excellent thermal properties.

Similar to a ‘no-bake’ cake at this stage, the solid but still soft mix is separated from the mould and cut to form the right-sized panels for the batch. Any waste is recycled. The manufacturing process doesn’t stop there however. The uncured AAC panels are ‘baked’ under elevated heat and steam pressure in one of the eight autoclaves at the Somersby facility. The panels are ready when they’re hardened or cured.

Altogether you can see how the term AAC, short for autoclaved aerated concrete, was created.

Mixing sand, cement, lime and expansion agent with water to make Hebel AAC slurry.


Pouring slurry into mould with corrosion protected steel reinforcement in place.


In the pre-curing stage hydrogen gas, formed through chemical reaction of ingredients, foams causing wet mix to rise.

The solid yet soft AAC cake is cut into panels.

AAC is cured in one of 8 autoclaves under steam and pressure.

The manufacturing process is complete when the Hebel panels are packaged ready for shipping to customers in Australia and New Zealand where they’ll be used in a wide range of applications.

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