Calcium Silicate Hydrate (C-S-H)
Definition
The principal binding phase produced when Portland cement reacts with water; a gel-like material that gives concrete most of its strength and whose texture under the microscope reflects the water-to-cement ratio and curing history.
- Role
- Principal binding phase in hydrated Portland cement
- Structure
- Gel-like, amorphous
- Reflects
- Water-to-cement ratio and curing history
- Contribution
- Primary source of concrete strength
Common questions
How does examining C-S-H texture help in a structural failure investigation?+
Under microscopy the density and porosity of the C-S-H gel can indicate whether a mix was cured properly or used an excessive water-to-cement ratio, both of which weaken concrete, giving investigators physical evidence relevant to a construction defect or collapse case.
Is C-S-H the same substance in every concrete sample regardless of mix design?+
No. Its exact composition and morphology vary with the cement chemistry, water content, admixtures and curing conditions used, which is why its microstructure can be diagnostic when comparing a failed sample against specification requirements.
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...
- Carbonation Front
- The boundary in concrete where atmospheric CO2 has converted portlandite to calcite; the depth of this front (measured in millimetres) is used...
- 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...