Blast furnace slag is a byproduct of the process of the cast iron production during which big quantities of liquid slag are produced. The composition is similar to Portland cement one.
The slag acquires hydraulic characteristics if at the output of the furnace it is cooled abruptly and turned into porous granules called granular slag. These are afterwards ground to obtain a powder of fineness comparable to the cement one.
Slag can be blended to Portland cement in variable proportion.
| Typical Specifications as Received Basis | ||
| CaO | % | 31 |
| Al2O3 | % | 10 |
| Fe2O3 | % | 1 |
| MgO | % | 9 |