Belite (C2S)
Definition
Dicalcium silicate, 2CaO.SiO2. 15 to 30 percent. Hydrates slow, gives long-term strength beyond 28 days.
- Formula
- 2CaO.SiO2 (dicalcium silicate)
- Typical content
- 15 to 30 percent of Portland cement
- Hydration rate
- Slow
- Strength contribution
- Long-term, beyond 28 days
Common questions
Why does belite content matter when forensically dating or sourcing a concrete sample?+
The alite-to-belite ratio and other clinker mineral proportions vary by cement plant and production era, so quantifying belite alongside alite, aluminate, and ferrite phases can help distinguish cement sources or batches when comparing a questioned concrete sample against a known one.
How does belite's slow hydration affect failure analysis of a structure?+
Because belite keeps contributing strength gain well past 28 days, a structural failure investigation needs to account for the concrete's age at failure, not just its 28-day design strength, since actual in-place strength can be meaningfully higher by the time of an incident.
Related terms
- Alite (C3S)
- Tricalcium silicate, 3CaO.SiO2. Dominant clinker phase (50 to 70 percent). Hydrates fast, gives early strength up to 28 days.
- Aluminate (C3A)
- Tricalcium aluminate, 5 to 10 percent. Reacts violently with water, attacked by sulphate. SRC cement is low in C3A.
- C-S-H Gel
- Calcium silicate hydrate, the main hydration binder. Amorphous, broad hump on XRD.
- Clinker
- The nodular intermediate product of Portland-cement manufacture, consisting of C3S, C2S, C3A and C4AF mineral phases before grinding.
- Ettringite
- A calcium sulfoaluminate hydrate that forms early in cement hydration and can re-form later from delayed sulfate attack; its presence or alteration...
- Portland Cement
- A hydraulic binder produced by firing calcium and silica sources at 1450°C; the four clinker phases (C3S, C2S, C3A, C4AF) hydrate on...
- Portlandite
- Calcium hydroxide (Ca(OH)2) crystallised during cement hydration; a bright birefringent phase visible in thin section that dissolves progressively as concrete carbonates, providing...