Autoclaved aerated concrete (AAC) and non-autoclaved foam concrete are often confused due to their similar appearance and the same basic principle — a cellular structure with air instead of heavy aggregate. However, the difference between them is fundamental and affects durability, strength and geometric stability.
The key difference is the curing technology. AAC is processed in an autoclave at 10–12 bar pressure and around 190°C for 10–12 hours. Under these conditions, calcium hydrosilicate (tobermorite) is formed, which provides high strength at low density. Foam concrete cures under natural conditions without an autoclave, and its structure is less stable.
At similar density (B05–B07), AAC consistently has higher compressive strength (A2.5–A5.0 vs A1.0–A2.5 for foam concrete). Drying shrinkage of AAC is 0.3–0.5 mm/m, while foam concrete can shrink up to 2–3 mm/m, which directly affects wall cracking.
Thermal insulation at the same density is comparable for both materials (thermal conductivity 0.12–0.16 W/m·K). However, due to more precise geometry (±1–2 mm tolerance), AAC can be laid with thin-bed adhesive (2–3 mm), eliminating thermal bridges in joints. Foam concrete is usually laid with cement mortar (10–15 mm), which reduces the overall thermal performance of the wall.
For load-bearing structures (exterior walls, self-supporting partitions in multi-storey construction), AAC is preferred. Foam concrete is suitable for non-load-bearing partitions and insulating layers under budget constraints. When choosing, always request factory certificates and test reports for strength and thermal conductivity.
