Cement Grinding and Additives Questions and Answers

Answer: A

Correct answer: reduce clinker content while retaining performance

Both are latent hydraulic or pozzolanic materials, so they contribute to strength themselves rather than merely diluting the cement. Replacing clinker with them cuts the fuel, the process carbon dioxide and the cost together, and it uses a material that is otherwise a waste from another industry.

Answer: B

Correct answer: True

Slag and fly ash react more slowly than clinker - the pozzolanic reaction needs the calcium hydroxide that clinker hydration must first release - so early strength is lower. Later strength is often higher, and the heat of hydration is lower throughout, which is why blended cements suit mass concrete particularly well.

Answer: C

Correct answer: produces different finenesses for each constituent

In a mill both materials are subject to the same grinding, but the softer one breaks down faster and ends up finer. Since clinker and slag differ in hardness, intergrinding gives each an unintended fineness, and the harder one may be left too coarse - which is why separate grinding is sometimes preferred.

Answer: D

Correct answer: Both A and R are true, and R is the correct explanation of A

Both are true and the reason gives the mechanism. Slag is harder than clinker and reacts more slowly, so it wants to be ground finer, not coarser. Intergrinding gives the opposite result. Grinding each to its own optimum and blending afterwards costs an extra mill and gives a better product.

Answer: A

Correct answer: reduces the specific energy consumption of the circuit

The roller press applies compression, which breaks particles far more efficiently than the impact of a tumbling ball charge. Pre-crushing the feed leaves the ball mill much less work per tonne, so the circuit’s energy per tonne falls substantially and its capacity rises.

Answer: B

Correct answer: True

Cement grinding takes roughly 35 to 45 kilowatt hours per tonne against 15 to 25 for raw grinding, because the clinker is harder and must be taken very much finer. It is the largest single electrical load on a cement plant, which is why so much attention is paid to separators, roller presses and grinding aids.

Answer: C

Multiplying 35 by 1.5 million gives 52.5 million kilowatt hours. Consumption on this scale is why even a small improvement in grinding efficiency repays substantial capital expenditure. Grinding is the single largest electrical load at most works.

Answer: D

Dry storage prevents pre-hydration and the silo also evens out short-term variation between mill batches. Open storage would ruin the product within days in most climates. Even a covered store must be kept dry to be of any use.

Answer: A

Both are true and the reason gives the second purpose: a customer receives an average of recent production rather than whatever the mill happened to make in the last hour, which improves the consistency of what is delivered.

Answer: B

Bulk tankers deliver directly into a silo at the batching plant, which suits any user of reasonable size. Bags remain necessary for small quantities and for sites without silo capacity. Bulk delivery accounts for the great majority of cement sold.