Blast-furnace cement is a type of cement in which part of the Portland cement clinker is replaced by ground granulated blast-furnace slag, a by-product of iron production. In the European cement standard (EN 197-1) this is called CEM III. Because it contains less clinker and the slag is a useful raw material, blast-furnace cement has a lower CO₂ footprint than ordinary Portland cement (CEM I).
Composition
The proportion of blast-furnace slag determines the type:
- CEM III/A — approximately 36 to 65% slag
- CEM III/B — approximately 66 to 80% slag
- CEM III/C — approximately 81 to 95% slag
Properties
- More resistant to aggressive water, sulphates and chlorides — hence widely used in civil and hydraulic engineering
- Lower heat of hydration — less risk of cracking from heat development in thick concrete
- Slower hardening — the early strength develops more slowly, especially in cold conditions; the final strength is excellent
- Lighter colour than Portland cement
Application
Blast-furnace cement is widely used for foundations, cellars, quay walls, bridges and other structures that stand in or near (ground)water. For its lower environmental impact it is also a frequently chosen binder in housing. In cold weather you must allow for the slower hardening.
Related terms
- Cement
- Portland cement
- Blast-furnace slag and steel slag
- Concrete
- Binder
- Hydration
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