Raw Materials and Quarrying Questions and Answers

Answer: C

Dolomitic limestone therefore has to be blended down or avoided, since magnesia hydrates long after the concrete has set and expands within it. Standards cap the magnesia content of the finished cement for exactly this reason.

Answer: D

The reaction between alkalis and certain reactive aggregates produces an expansive gel that cracks the concrete years after construction. Where such aggregates are in use, a low-alkali cement is specified to avoid the problem.

Answer: A

Volatile compounds evaporate in the hot zone and condense in the cooler preheater, gradually blocking it. A bypass is fitted to bleed off part of the gas stream where chloride input is high, at some cost in fuel efficiency.

Answer: B

They evaporate in the burning zone and condense again in the cooler parts of the preheater, cycling within the system rather than leaving it. The build-up they cause is a recognised operating problem and is managed by a bypass rather than by tolerating it.

Answer: C

Both are true and the reason gives the necessity: unless part of the circulating load is removed, the coatings grow until the preheater blocks and the kiln has to be stopped. The bypass costs fuel but buys continuous operation.

Answer: D

Correct answer: loading and haulage of the broken stone to the crusher

The sequence is drill, blast, load, haul, crush. Blasting reduces the face to fragments a shovel can lift and a crusher can accept, and the crusher then brings the stone down to the size the grinding mill needs. Nothing is ground, blended or burned before the material has been crushed.

Answer: A

This is coarse enough for the crusher to handle economically and fine enough for the raw mill to take. Reducing the stone all the way to meal in one machine would be far less efficient than splitting the duty between crusher and mill.

Answer: B

Crushing reduces large lumps to a manageable size by compression or impact, while grinding takes that product down to a powder. They differ in the size range, the machines used and the energy consumed per tonne, so the distinction is a real one.

Answer: C

Material laid down in long layers and reclaimed across them averages out the variation between one part of the quarry face and another. Steady chemistry entering the mill is what makes steady clinker possible downstream.

Answer: D

Both are true and the reason gives the purpose of the arrangement: a cut taken across many layers contains a little of everything stacked, so short-term variation in the quarry is smoothed before the material ever reaches the mill.