Raw Materials and Quarrying Questions and Answers

Answer: C

The soil and subsoil stripped at the outset are kept for this purpose, which is one reason they are stored rather than discarded. Restoration is generally a condition of the planning permission rather than a voluntary act.

Answer: D

The first two are correct. The third misplaces the gypsum, which is interground with the cooled clinker after burning, since its purpose is to retard a compound the kiln has already formed and it would decompose at kiln temperatures anyway.

Answer: A

Using them replaces material that would otherwise be dug and burnt, which saves both quarrying and emissions. Their supply depends on other industries continuing to produce them, which is a real constraint on how far they can be relied upon.

Answer: B

It is a by-product, so its availability is governed by an industry with quite different drivers. Plants that depend heavily on it are exposed to decisions taken elsewhere, which is a consideration when planning long-term substitution.

Answer: C

Both are true and the reason gives the difficulty: the material that has done most to reduce clinker content is becoming scarcer as its source disappears, so the industry is having to look to calcined clays and other substitutes.

Answer: D

The technique gives the full oxide composition within minutes, which is fast enough to control the raw mix as it is being prepared. Drying, setting and sieving each measure something useful but none gives the chemistry.

Answer: A

The proportions are solved so that the lime saturation factor, silica modulus and alumina modulus all fall in their target ranges. Cost enters afterwards as a constraint on the solution rather than as its starting point.

Answer: B

Correct answer: False

The proportions are adjusted continuously. The chemistry of the stone changes as the face advances, the corrective materials vary, and the target moduli must be held within narrow limits, so an analyser samples the raw meal and a control system trims the feeders in response. Fixing the proportions once would let the lime saturation factor drift far outside the range the kiln can burn.

Answer: C

Grindability affects the electrical consumption of the plant directly, and a hard stone raises the cost of every tonne processed. Chemistry and physical hardness are separate properties and a deposit may be excellent in one and awkward in the other.

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. Grinding is the largest electrical load in a cement works, and the energy it takes depends on the hardness and grindability of the stone rather than on its chemistry. A hard, siliceous limestone can therefore cost appreciably more per tonne of raw meal than a soft chalk of identical analysis.