Raw Materials Preparation
| The raw materials used in the manufacture of cement are limestone, clay and iron ore, typical chemical compositions of which are given in table 5. Limestone makes up approximately 80% of the raw material requirements, composes of mainly calcium carbonate with small intrusions of magnesium carbonate. Quarrying operations are geared to minimizing the intrusions. The limestone is crushed to less than 75mm. MgO in the cement, if present in sufficient quantities will cause expansion upon hydration thus resulting in unsoundness in the concrete. |
Typical Composition of some raw materials
| Component |
SiO2 |
Al2O3 |
Fe2O3 |
CaO |
MgO |
SO3 |
K2O |
Na2O |
LOI |
| Limestone |
2.68 |
0.62 |
0.46 |
51.85 |
1.94 |
0.03 |
0.05 |
0.02 |
42.52 |
| Sandy clay |
81.56 |
11.29 |
1.79 |
0.12 |
0.09 |
0.05 |
0.14 |
0.03 |
4.91 |
| Clay |
65.18 |
21.91 |
3.36 |
0.11 |
0.08 |
0.06 |
0.19 |
0.04 |
9.11 |
| Iron ore |
14.88 |
16.79 |
57.74 |
0.12 |
0.56 |
0.04 |
0.04 |
0.03 |
9.87 |
| Shale |
61.10 |
16.42 |
7.01 |
1.02 |
2.34 |
0.01 |
4.12 |
1.65 |
3.71 |
| Sand |
94.70 |
2.90 |
0.24 |
0.35 |
0.13 |
0.01 |
0.60 |
0.21 |
0.91 |
| Bauxite |
3.11 |
57.59 |
15.74 |
4.16 |
0.16 |
0.29 |
0.08 |
0.08 |
15.40 |
| Gypsum |
4.31 |
0.34 |
0.14 |
31.19 |
0.11 |
43.88 |
- |
- |
19.39 |
| Fuel Ash |
57.20 |
17.36 |
9.11 |
3.95 |
1.80 |
3.40 |
0.78 |
2.50 |
- |
Due to the variable nature of these three components, they are pre-blended prior to their use. Here in Tasek, limestone is crushed and stored in a covered circular storage dome, utilizing the chevron pile stacking method. In this method, stacking takes place at one end of the pile. At the other end of the pile the limestone is reclaimed and then stored in a silo. Clay and iron ore are crushed in a crusher and are then stored in a storage hall. Prior to use the two components are reclaimed and stored in intermediate silos.
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