Concrete Technology Questions and Answers

Answer: B

Tricalcium silicate (C3S, about 40 to 50 percent) and dicalcium silicate (C2S, about 25 to 30 percent) together make up the greatest part, around 70 to 75 percent, of ordinary Portland cement. They are responsible for its strength. Tricalcium aluminate (C3A) is about 8 to 12 percent and tetracalcium aluminoferrite (C4AF) is about 8 to 12 percent, so any combination that includes one of those two is smaller. Hence the C3S and C2S pair has the largest share.

Answer: C

The correct matching is 1-C, 2-D, 3-A, 4-B. Portland slag cement has good resistance to chemical attack, so it protects reinforcement from corrosion (1-C). Low heat Portland cement gives off less heat of hydration and is used in massive water-retaining structures such as dams (2-D). Rapid hardening cement gains strength quickly, which makes it suitable for cold weather concreting (3-A). Super sulphated cement resists sulphates and sea water, so it suits offshore structures (4-B). The other codes swap these pairs.