Sand Lime Block Calculator: Complete Reference
Calcium Silicate (Sand-Lime) Block Basics
Calcium silicate bricks and blocks are manufactured from quartz sand (85–90%) and quicklime (10–15%) pressed to form and then autoclaved at 170–190°C under 8–10 bar steam pressure. The calcium silicate hydrate (CSH) formed gives compressive strength of 12–35 MPa.
Properties: Density 1700–2100 kg/m³, thermal conductivity λ = 0.70–0.85 W/m·K, dimensional accuracy ±1mm, available in white/off-white. Standards: EN 771-2 (Europe), AS/NZS 4456 (Australia).
Mix Design & Autoclaving
Standard mix: 10:1 sand:lime by mass + 8% moisture. Press at 15–25 MPa. Autoclave 8–16 hr at 170°C, 8 bar. Higher lime (8:1 ratio) increases strength to SB 25–35. Lower ratio (12:1) gives economy grade SB 12–15. Strength classes: SB 12, 15, 20, 25, 35 (MPa).
Thermal & Structural Performance
λ = 0.70–0.85 W/m·K. 240mm wall: U ≈ 2.0–2.5 W/m²K — external insulation required for energy codes. Good sound insulation: 240mm wall Rw ≈ 50 dB. Compressive strength 15–35 MPa — suitable for load-bearing walls in buildings up to 10+ storeys.
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FAQs
What is the difference between sand-lime and clay brick?
Sand-lime bricks are manufactured (autoclaved), giving uniform white colour, ±1mm tolerance, and consistent strength. Clay bricks are fired (variable colour, ±3–5mm tolerance). Sand-lime typically has slightly higher density and similar compressive strength, but worse thermal performance than high-insulation clay products.
Can sand-lime blocks be painted?
Yes. The smooth white surface accepts paint directly without primer in most cases. Use breathable mineral or silicate paints for external use to allow vapour diffusion.