Portland cement clinker is a dark grey nodular material made by heating ground limestone and clay at a temperature of about 1400-1500°C. The nodules are ground up to a fine powder to produce cement, with a small amount of gypsum added to control the setting properties.
| Typical Specifications as Received Basis | ||
| CaO | % | 63 – 68 |
| SiO2 | % | 20 – 22 |
| Al2O3 | % | 5 – 7 |
| Fe2O3 | % | 2 – 4,5 |
| MgO | % | 0,8 – 3 |
| SO3 | % | 0,3 – 1 |
| Na2O+0,658K2O | % | 0,4 – 1,2 |
| C3S | % | 56 – 62 |
| C2S | % | 10 – 23 |
| C3A | % | 7 – 14 |
| C4AF | % | 7 – 14 |
| L.S.F. | % | 92 – 100 |
| Density | g/cm3 | 1,3 – 1,5 |
| Setting Time | Initial | 110 – 150 min. |
| Final | 200 – 250 min. | |
| Compressive Strenght | 2 days | 18 – 23 MPa |
| 28 days | 46 – 52 MPa |