Blaine specific surface calculator

What this measures

Specific surface area (S) is the total surface of all particles in one gram of material. Blaine air permeability relates measured air-flow time t through a compacted powder bed to S, using the bed porosity e, cement density ρ, air viscosity η, and an apparatus device constant K found by calibration on reference cement.

Unit	Meaning
cm²/g	Common on Blaine reports (e.g. 48 800)
m²/kg	SI-friendly; 1 cm²/g = 0.1 m²/kg

Finer grinding increases surface area, lengthens flow time, and increases S.

General formula

S = (K/ρ) · (√e³ / (1−e)) · (√t / √(0.1·η))

• S — cm²/g; ρ — g/cm³; e — bed porosity (0–1); t — s; η — Pa·s from air temperature (Sutherland).
• K — dimensionless constant for your cell, preparation, and procedure (reference cement calibration).

Simplified shortcut

At e = 0.500 and ~20 °C (fixed η):

S = (524.2 · K / ρ) · √t

Use the General mode when porosity or lab temperature differ from standard practice.

Device constant K

K is not a universal physical constant. Invert the formula with a certified reference cement (S_ref, measured t_ref, same ρ, e, temperature) — see Advanced options on the calculator.

Bed volume and specimen mass

Before measuring t, prepare a bed at target e:

• V = (m₂ − m₃) / ρ_H (cm³) from mercury masses, or enter V manually if already known.
• m = (1 − e) · ρ · V (g) — at e = 0.5, half the bed volume is solid cement.

Common errors

Issue	Effect
Assuming e = 0.5 while the bed is off-spec	Systematic bias in S
Ignoring temperature with the simplified formula	Slight S drift
Wrong ρ or stale K	Scaled or shifted results
Poor compaction or cracked bed	Scattered t, repeat test

Disclaimer

This tool supports training and cross-checks. EN 196-6, ASTM C204, and your accredited quality system define binding requirements for apparatus, bed preparation, and reporting.