Clinker Formation and Phases Questions and Answers

Answer: C

Correct answer: 1 and 2 only

Statements 1 and 2 describe the sequence correctly: belite forms first by solid-state reaction, and alite forms later when belite takes up further lime in the presence of the melt. Statement 3 skips the intermediate, which is not how the reaction proceeds - and it is precisely because alite forms from belite that a shortage of lime leaves belite unconverted.

Answer: D

Both are consequences of the alite-forming reaction not going to completion, so the two rise together. This pairing is a useful diagnostic when clinker quality is being assessed. One figure alone would be far less informative than the pair.

Answer: A

Kiln and mill do not have to run at the same times, and a stock lets each be operated to its own best advantage. Prolonged exposure to damp air is undesirable, so covered storage is normally used. Clinker silos also keep the material dry and easy to handle.

Answer: B

Correct answer: False

Clinker is anhydrous and prehydrates on exposure to moisture, the free lime slaking and the aluminate and silicates reacting at their surfaces. The result is a cement of lower strength and altered setting, so clinker is stored under cover and stock is rotated rather than left indefinitely.

Answer: C

Composition sets the ceiling and fineness governs how quickly that potential is realised. Nodule size and colour are useful operating indicators but do not themselves determine strength. Composition and fineness together settle what the cement can achieve.

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. Hydration begins at the surface, so the same phases ground finer present more surface and react faster. Two cements from one clinker can therefore differ substantially in early strength, and fineness is the variable a mill operator uses to control it.

Answer: A

These are the two fastest-reacting phases and therefore the two that release heat soonest. Reducing them in favour of belite is exactly how a low heat cement is formulated for use in mass concrete. Heat and early strength cannot readily be separated from one another.

Answer: B

Correct answer: lower early strength and less heat evolved

Alite hydrates rapidly and evolves considerable heat; belite hydrates slowly and evolves little. Trading ten points of alite for ten of belite therefore reduces both the early strength and the heat - which is exactly the formulation wanted for mass concrete, where the later strength is recovered and the heat is a liability.

Answer: C

Correct answer: True

A low-heat or low-early-strength cement is made deliberately, by raising the belite at the expense of the alite. It suits mass pours such as dams and thick rafts, where rapid hydration would crack the concrete thermally. The strength arrives later, and specifications for such work are commonly written at 56 or 90 days.

Answer: D

The proportion of aluminium to iron varies continuously, so the conventional formula represents one point on a range rather than a fixed compound. This is one reason Bogue figures are estimates rather than measurements.