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How are cement raw materials blended to achieve the correct chemical composition?

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Cement The cement-making process, from crushing and grinding of raw materials, through roasting of the ground and mixed ingredients, to final cooling and storing of the finished product.

To achieve the correct chemical composition for cement, manufacturers employ a multi-stage approach to blending raw materials:

Initial Control: A first approximation of the required composition is established through selective quarrying and by controlling the raw materials fed into the crushing and grinding plant.1
Refinement: Finer control is achieved by drawing material from two or more batches that have slightly different compositions.1
Mixing Processes:
- Dry Process: The raw mixes are stored in silos, where thorough blending is maintained through agitation and vigorous circulation induced by compressed air.1
- Wet Process: The materials are processed into a slurry, which is stirred in tanks using mechanical means, compressed air, or a combination of both.1

In cases where natural deposits do not meet the necessary chemical standards, beneficiation processes such as froth flotation may be used to remove excess silica or alumina to upgrade the limestone, though this is typically reserved for when it is unavoidable due to the high costs involved.2