Types of Cement and Composition Questions and Answers

Answer: A

Both are true and the reason gives the design logic: repointing a joint is straightforward whereas replacing cracked units is not, so the weaker material is placed where failure can be tolerated. A strong mortar in a weak wall moves the cracking into the bricks.

Answer: B

The first two are correct. The third is usually the reverse of the truth, since blended cements often give a denser paste and better resistance to chemical attack. The slower early gain is the real trade-off rather than durability.

Answer: C

Most of the emission comes from calcining limestone and burning fuel to make clinker, so any replacement cuts it proportionately. This is the most widely used route to lower-carbon cement. It also puts an industrial by-product to use rather than landfilling it.

Answer: D

Seventy per cent of 800 is 560, ignoring the smaller emissions from processing the slag itself. The calculation shows why substitution is the industry's most direct lever on emissions. Further reduction requires changing the fuel or capturing the carbon dioxide.

Answer: A

A needle of standard weight and diameter is allowed to penetrate a paste of standard consistency. Blaine measures fineness and Le Chatelier measures soundness. Each test has its own apparatus and its own standard procedure.

Answer: B

Calcium sulphate is the gypsum added after burning rather than a clinker mineral formed in the kiln. The other three are all products of the burning process. Distinguishing what the kiln makes from what is added later matters here.

Answer: C

It is interground with the cooled clinker afterwards, precisely because its purpose is to control the reaction of a compound the kiln has already made. Adding it before burning would defeat that purpose. Gypsum would decompose at kiln temperatures in any case.

Answer: D

A finer cement presents more surface to water and so hydrates faster, which is why rapid hardening cements are ground finer. Grinding beyond a point costs more energy than the gain justifies. Grinding is among the largest electrical loads in a cement works.

Answer: A

Both are true and the reason gives the mechanism: hydration proceeds at the particle surface, so dividing the same mass into smaller particles multiplies the area at which the reaction can begin. Fineness is therefore one of the main levers on early strength.

Answer: B

Correct answer: about one third greater

\[ \frac{400}{300} = 1.33, \] so B has about a third more surface for the same mass. Fineness governs the rate of hydration, since reaction happens at the surface, so B will gain early strength faster and generate heat faster - and cost more to grind, since grinding energy rises steeply with fineness.