Carbonation Front
Definition
The boundary in concrete where atmospheric CO2 has converted portlandite to calcite; the depth of this front (measured in millimetres) is used to estimate exposure age under known humidity and CO2 conditions.
- Chemical change
- Portlandite converted to calcite by atmospheric CO2
- Measured in
- Millimetres of depth
- Use
- Estimating exposure age under known humidity/CO2 conditions
Common questions
What factors affect how fast the carbonation front advances?+
Ambient CO2 concentration, relative humidity, concrete permeability, and the water-to-cement ratio of the original mix all influence carbonation rate, which is why age estimates from front depth require knowledge of the structure's specific exposure history.
How does carbonation front depth differ from carbonation depth as a measurement?+
They describe the same physical boundary, the carbonated-to-uncarbonated transition in the concrete, but 'front' emphasizes its use for dating exposure age under known conditions, while 'depth' is more often cited as a durability or corrosion-risk indicator.
Can the carbonation front depth be used to date when a structure was built?+
Only approximately, and only when the local humidity and CO2 exposure history are reasonably well known, since the same front depth could result from different combinations of structure age and environmental exposure rate.
Related terms
- Aggregate
- The granular filler (sand, gravel, crushed rock) that occupies 60-80% of a concrete volume; its mineralogy, grain shape, and size distribution are...
- Calcium Silicate Hydrate (C-S-H)
- The principal binding phase produced when Portland cement reacts with water; a gel-like material that gives concrete most of its strength and...
- Ettringite
- A calcium sulfoaluminate hydrate that forms early in cement hydration and can re-form later from delayed sulfate attack; its presence or alteration...
- Petrographic Thin Section
- A slice of material ground to 30 micrometres and mounted on a glass slide for transmitted polarised light microscopy; the standard tool...
- 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...