Terminology

• Calcium silicate board: panel of hydrated calcium silicate with fibers or fillers
• Semi-compressed board: denser board pressed during manufacture

Composition and production

Raw materials

• Hydrated calcium silicate with natural or man-made fibers or fillers (ASTM C656)
• Some manufacturers describe the board as Portland cement with selected fibers and fillers

Properties

Physical

• Density: semi-compressed board about 1,300 kg/m3 (about 81 lb/ft3); 6 to 12 mm board 975 kg/m3 (about 61 lb/ft3)

Thermal and moisture

• Thermal conductivity: 0.187 W/(m·K), about 1.3 Btu·in./(h·ft2·°F) for a semi-compressed board
• Keeps structural integrity after immersion in water

Fire behavior

• Classified A1 noncombustible per EN 13501-1

Standards

Material specifications

• ASTM C656: structural insulating board, calcium silicate

Uses in buildings

Building elements

• Fire-Rated Assemblies: fire-resistive boards
• Wall Cladding: external wall rain screen, eaves, fascia, and soffit linings
• Metal Stud Walls: internal drywalls

Pros and cons

Pros

• Noncombustible
• Resists moisture effects
• Can be painted, papered, or tiled

Cons

• Denser than gypsum board at about 975 to 1,300 kg/m3

Manufacturing and cost

Main manufacturers and suppliers

• Promat

Sources

• ASTM: C656-17(2023), https://store.astm.org/c0656-17r23.html
• Promat: Masterclad product data sheet, https://media.promat.com/pi658886/original/272012565/promat-pds-masterclad-asia-en-2023-03.pdf
• Wikimedia Commons: Promat calcium silicate boards.jpg, photo by Achim Hering (CC BY 3.0), https://commons.wikimedia.org/wiki/File:Promat_calcium_silicate_boards.jpg