1 Which one of the following four main compounds in cement i

1. Which one of the following four main compounds in cement is responsible for the long-term strength gain in concrete? a. Tricalcium silicate (C3S) b. Dicalcium silicate (C2S) c. Tricalcium aluminate (C3A d. Tetracalcium alumino-ferrite (CAAF) 2. The loss of excessive moisture from the surface of concrete in plastic state leads to: b. Bleeding c. Plastic shrinkage d. Plastic settlement 3. The chemical reaction between water and cement that results in rapid strength development is known as a. Hydration c. Bleeding d. Shrinkage Which of the following types of water is not suitable for using in the concrete mix for reinforced concrete structures? a. b. c. d. Tap water Sea water Recycled concrete wash water All of the above 5. Materials that react chemically with calcium hydroxide, a byproduct of hydration reaction, in the presence of moisture to form cementitious compound are called: a. b. c. d. Hydraulic materials Pozzolanic materials Portland cement Calcium silicate hydrate 6. The main source of fy ash is: Cement industry Nuclear power plants Thermal power plants burning coal Iron industry a. b. C. d.

Solution

Answer 1. (b) Dicalcium Silicate (C₂S)

The contribution of C₂S to the strength of the cement paste will be slow initially but C₂S is responsible for the long-term strength of cement concrete.

Answer 2. (c) Plastic Shrinkage

the excessive water loss from the surface of the concrete( through evaporation) will cause the concrete to shrink rapidly and crack. the cracks will appear as tensile stress are relieved due to shrinkage.

Answer 3. (a) Hydration

heat of hydration involves in rapid strength development.

Answer 4. (b) Sea Water

According to Research analysis sea water is not suitable for the mixing and curing of both plain and reinforced concrete.

Answer 5. (b) Pozzolanic Materials

Pozzolanic materials are  finely divided form and in the presence of water, react chemically with calcium hydroxide at ordinary temperature to form compounds possessing cementitious properties.

Answer 6. (c) Thermal power plants burning coal

The fly ash produced from the burning of pulverized coal in a coal

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