Autoclaved Aerated Concrete (AAC) overturns the concept of heavy masonry. It is a monolithic material that simultaneously performs the functions of load-bearing structure and excellent thermal insulation, without the aid of additional insulation layers.
The mix is composed of siliceous sand, cement, lime and water. The secret lies in the addition of aluminium powder, which reacts alkalinically, developing hydrogen gas and doubling the volume of the mixture. After cutting, the blocks are cured in a saturated-steam autoclave (190 degrees C at 12 bar). This process chemically transforms the binders into tobermorite, a silicate mineral that confers absolute dimensional stability. The final product has virtually zero post-production shrinkage, unlike traditional fired bricks.
The closed-pore structure makes AAC an excellent thermal insulator. Laying is done with adhesive mortar applied with a notched trowel (2-3 mm thick): this eliminates the thermal bridge typical of the thick mortar joint of traditional brickwork. A 40 cm block alone achieves thermal transmittance U values below 0.20 W/m2K, satisfying nZEB regulations without additional layers.
Standards
European and international references applicable.
Physical properties
Usage environment
Dedicated fixings (long plugs specific for AAC or chemical anchors) are mandatory. Protect the base from capillary moisture: always install a damp-proof course at foundation level.