Raw Materials and Quarrying Questions and Answers

Answer: A

Twenty multiplied by 3,000 gives 60,000 kilowatt hours each day. Figures of this order are why grindability is taken as seriously as chemistry when a deposit is being assessed. Grinding typically accounts for well over half the electricity a works uses.

Answer: B

Correct answer: the energy required to reduce it to a given fineness

The Bond work index is the energy in kilowatt hours per tonne needed to reduce material from a notionally infinite size to eighty per cent passing 100 micrometres, and it is the standard basis for sizing crushers and mills. It is a measured property of the material, which is exactly what lets two chemically identical limestones be compared on grinding cost.

Answer: C

The first two are correct. The third is wrong, since blasted stone contains pieces far too large for any mill and must pass through a primary crusher first, which is why the crusher is generally sited at or near the quarry.

Answer: D

The two differ in structure and in the organisms they contain, and mixing them makes restoration much less successful. Keeping them apart costs little at the time and materially improves what can be done with the site afterwards.

Answer: A

Correct answer: protect the health of workers and nearby residents

Respirable dust from haul roads causes silicosis and other respiratory disease, and it carries beyond the site boundary to neighbours. Suppression by watering or with binders is therefore a health control first, and a permit condition at most quarries. Visibility and community relations benefit too, but they are not the reason it is required.

Answer: B

Correct answer: False

Appearance is the smallest part of it. Quarry controls cover dust and its health effects, blast vibration and airblast, noise, groundwater and surface water quality, ecological impact and habitat, and the restoration of the site after working ceases - the last usually secured by a bond lodged before extraction begins.

Answer: C

Correct answer: limiting the charge weight detonated at any one instant

Ground vibration depends on the charge weight fired per delay rather than on the total in the blast, so millisecond delay detonators are used to split a large blast into many small ones a few milliseconds apart. The rock is broken as required while the peak particle velocity at the nearest building stays within limits - and firing at night would raise complaints rather than settle them.

Answer: D

Both are true and the reason explains the apparent paradox: a well-sequenced large blast may have a smaller instantaneous charge than a poorly designed small one, and it is the instantaneous figure that the ground responds to.

Answer: A

They substitute for material that would otherwise be dug, and they give a use to something that would otherwise be discarded. Their composition has to be checked carefully, since waste streams vary far more than quarried stone does.

Answer: B

The kiln destroys organic matter but not the elements themselves, and chlorides, alkalis and heavy metals all pass through into the clinker or the gas stream. Incoming waste materials are analysed at least as carefully as quarried ones.