Raw Materials and Quarrying Questions and Answers

Answer: A

Calcium carbonate makes up the great bulk of the raw mix, usually around four fifths of it by mass. Clay supplies the silica and alumina, while bauxite and iron ore are used only as small corrective additions when the main materials fall short.

Answer: B

These oxides combine with the lime during burning to form the silicate and aluminate phases of the clinker. Without them the kiln would produce quicklime rather than cement, so the proportion of clay is one of the first things a plant controls.

Answer: C

Sand, iron ore or bauxite are added in small quantities to bring silica, iron or alumina to the target figure. The quantities involved are usually only a few per cent, but they matter because the moduli governing burnability are sensitive to them.

Answer: D

Iron lowers the temperature at which the charge begins to melt and forms the ferrite phase in the clinker. Gypsum is added after burning and slag is a blending component rather than a raw mix corrective, so neither belongs in this list.

Answer: A

What matters is that the oxides are present in the right proportions, not that any one material is pure. Plants routinely blend materials of variable quality and correct the mix, which is why raw mix design is a continuous exercise rather than a one-off calculation.

Answer: B

Both are true and the reason gives the economics: moving several tonnes of stone for every tonne of cement produced would dominate the cost, so the plant goes to the deposit rather than the deposit to the plant. Fuel and corrective materials, needed in far smaller quantities, are brought in instead.

Answer: C

Correct answer: 2,400 tonnes

\[ 3000 \times 0.80 = 2400\ \mathrm{tonnes}. \] The remaining 600 tonnes is the clay, shale, iron and sand that make up the rest of the mix. Limestone dominating the raw meal to this extent is why a cement works is sited on its quarry rather than near its market - hauling the stone would cost more than distributing the cement.

Answer: D

It must be stripped and stored before extraction can begin, and the depth of it strongly affects whether a deposit is worth working. Well-run quarries keep the material for restoring the site once the stone is exhausted.

Answer: A

Correct answer: the overburden that must be removed for each unit of useful stone

The stripping ratio is waste over product, and it governs the economics of the deposit directly: every tonne of soil and barren rock moved must be paid for and gives nothing in return. A deposit of excellent chemistry under deep overburden can be worth less than a poorer one lying at the surface.

Answer: B

Depth of overburden, distance from the works, the presence of harmful impurities and planning constraints can all rule out a chemically excellent deposit. Quality of the stone is only one of several conditions that have to be satisfied together.