Calcium Silicate Boards

Calcium silicate is a rigid, machinable insulation board made by hydrothermal reaction of lime, silica and reinforcing fibre. It has low thermal conductivity (0.06–0.09 W/mK), good compressive strength (4–8 MPa), and is non-combustible. Used as block insulation in petrochemical pipework, power plant boilers, ducts, ladle covers, and back-up insulation behind dense refractory.

Standard calcium silicate is rated for continuous service to 650°C, with peak excursions to 750°C. Above this, dehydration of the silicate matrix causes shrinkage and strength loss. For higher temperatures, switch to ceramic fibre (to 1430°C) or microporous insulation (to 1000°C). Selection depends on temperature, mechanical loading and humidity exposure.

Calcium silicate is hygroscopic, it absorbs ambient moisture. Modern boards include water-repellent silicone treatment, but prolonged outdoor exposure or wet-bulb conditions still degrade the insulation. For outdoor pipe insulation use a properly sealed cladding (aluminium or stainless steel) with sealed seams and weather-jacketing on horizontal runs.

Rockwool: lower cost, lower temperature limit (650°C), and lower compressive strength, used for general lagging. Calcium silicate: higher compressive strength, machinable, supports loads, used in ducts, boilers and below-grade pipe. Microporous: 30–40% lower thermal conductivity at high temperatures, much higher cost, used where space and weight are constrained (ladle covers, kilns, aerospace).

Standard board thicknesses are 25, 38, 50, 65, 75 and 100 mm in 600×900 mm or 1000×500 mm sheets. Pipe sections are pre-formed for nominal pipe sizes 25 to 600 mm in 25 or 50 mm wall thickness. Custom thickness and density grades are made to order. We supply Divine Cerawool calcium silicate as our standard authorised line.

Yes, calcium silicate is highly machinable. Use a hand saw, jigsaw or table saw with a wood blade. Drill, screw and rebate it like a soft hardwood. Always wear an FFP3 dust mask, the silica dust is hazardous. Off-cuts can be reused for filling small gaps. Mortar joints between boards use a calcium-silicate based jointing compound.