Compressive strength
This is the material’s resistance to damage by external forces causing deformation and internal stresses. The compressive strength of autoclaved aerated concrete depends on its density and the degree of moisture. The lowest compressive strength declared by the manufacturer should be 1.5 [N/mm2] at a concrete moisture content of 6 ± 2% by weight and should be expressed as an average or characteristic value of the element in compression. Autoclaved aerated concretes with different compressive strength classes are produced. They are also related to the minimum classes of compressive strength, which are also specified in the national annexe to the PN-EN 771-4 standard.
Minimum compressive strength classes of ABK masonry units in relation to the dry gross density classes:
| Class of dry gross density | Minimum compressive strength class |
| 300, 350, 400 | 1,5 |
| 450, 500, 550 | 2,5 |
| 600, 650 | 3 |
| 700, 750 | 4 |
| 800, 900, 1000 | 5 |
Strength class means the average compressive strength in N/mm2.
Blocks are available in the following density classes and average strengths:
| Gross density [kg/m3] | Average compressive strength [N/mm2] |
| 400 | 2 |
| 500 | 2,5 |
| 600 | 3 |
| 700 | 4 |
