Q1: Good quality cement contains higher percentage of

ANS:A - Tricalcium silicate

Option A is correct because the question was about an overall higher percentage. So as calculated,
1) Tricalcium silicate is 30-50%.
2) Di-calcium silicate is 20-45%.
3) Tri-calcium aluminate is 8-12%.
4) Tetra calcium alumino ferrite is 6-10%. Tricalcium silicate is the right answer.

Because it gives the early strength if there is no early strength in concrete structure then what is the profit?

No one wt for 2-3 years for gaining complete strength by di calcium silicate. So right answer is option A. During Reaction C3S & C2S:- C-S-H & Ca (OH) 2 formed, CSH is the good properties of conc. Makes up 50-60% vol. Solid.

And that reactions seen C3S produces lesser quantity C-S-H and more quantity Ca (OH) 2 and that is not desirable product in concrete mass it is soluble in water makes conc. Porous, and also the quality density of C-S-H formed out C3S is slightly inferior to that form by C2S. The good quality of cement contains;

50% of tricalcium silicate- for rapid strength and quick setting of cement.
30% of dicalcium silicate- hardens slowly and responsible for long term strength.
10% of tricalcium aluminate-quick action with water.
10% of tetra calcium Aluminoferrate.
5% of Gypsum.