Aluminate (C3A)
Definition
Tricalcium aluminate, 5 to 10 percent. Reacts violently with water, attacked by sulphate. SRC cement is low in C3A.
- Compound
- Tricalcium aluminate
- Typical content
- 5 to 10 percent of cement
- Reactivity
- Violent with water; attacked by sulphate
- SRC cement
- Formulated with low C3A
Common questions
Why is C3A content kept low in sulphate-resisting cement specifically?+
C3A is the phase most vulnerable to sulphate attack, which forms expansive reaction products such as ettringite that crack and degrade concrete, so reducing its proportion is the main chemical lever used to make cement resistant to sulphate-rich soils or groundwater.
How does C3A content become relevant in a forensic concrete failure case?+
Measuring the actual C3A content of a failed concrete element, compared against the specification for the environment it was placed in, can show whether the wrong cement type was used and whether that mismatch contributed to sulphate-related deterioration and structural failure.
Related terms
- Alite (C3S)
- Tricalcium silicate, 3CaO.SiO2. Dominant clinker phase (50 to 70 percent). Hydrates fast, gives early strength up to 28 days.
- Belite (C2S)
- Dicalcium silicate, 2CaO.SiO2. 15 to 30 percent. Hydrates slow, gives long-term strength beyond 28 days.
- 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...