[!abstract] Contents

• Terminology
• History and demand
  • Discovery and early use
  • Demand trend
• Composition and production
  • Raw materials
  • Manufacturing process
• Properties
  • Physical
  • Mechanical
• Uses in buildings
  • Building elements
  • Pros and cons
• Manufacturing and cost
  • Main manufacturers and suppliers
• Sources

Terminology

• AAC: autoclaved aerated concrete
• Aluminum powder: foaming agent at 0.05 to 0.08 percent by volume
• Thin-bed mortar: joint about 3.2 mm (1/8 in.) thick

History and demand

Discovery and early use

• Mid-1920s: Johan Axel Eriksson developed AAC; patented 1924
• 1929: production began at Yxhult, Sweden, under the Ytong name
• Siporex (Sweden, 1939), Hebel (Germany, 1943), Biltech (India, 1993)

Demand trend

• China has over 2,000 AAC plants producing about 190 million m3 per year (2025)

Composition and production

Raw materials

• Quartz sand, gypsum, lime, Portland cement, water, fly ash, and aluminum powder

Manufacturing process

• Hydrogen from the aluminum powder roughly doubles the raw mix volume, with bubbles up to 3 mm
• Autoclave cured about 12 hours at roughly 190°C (375°F) and 800 to 1,200 kPa (120 to 170 psi)

Properties

Physical

• Air content: up to 80 percent of block volume depending on density
• Density example: 400 kg/m3 (about 25 lb/ft3) under European class B2.5

Mechanical

• Compressive strength: up to about 8,000 kPa (1,200 psi), roughly 50 percent of regular concrete

Uses in buildings

Building elements

• AAC Walls: load-bearing and infill blocks and panels, often over 500 mm (20 in.) thick in cold climates
• Fire-Rated Assemblies: noncombustible wall units

Pros and cons

Pros

• Mostly air by volume, so units are light
• Drilled with high-speed steel bits without hammer action
• Thin-bed mortar joints

Cons

• About half the compressive strength of regular concrete
• Walls over 500 mm thick in cold climates to meet insulation standards

Manufacturing and cost

Main manufacturers and suppliers

• Aercon AAC
• Xella (Ytong, Hebel)

Trade association: Autoclaved Aerated Concrete Products Association.

Sources

• Wikipedia: Autoclaved aerated concrete, https://en.wikipedia.org/wiki/Autoclaved_aerated_concrete