Construction Materials and Construction Practices MCQs - JDO Exam

1. The shape of the brick gets deformed due to rainwater falling on hot brick. The defect is known as

(a) Chuffs

(b) Bloating

(c) Nodules

(d) Lamination

Answer: (a) Chuffs

Chuffs is a defect in bricks where the shape gets deformed due to rain falling on hot bricks during manufacture.

2. Pozzolanas are rich in:

(a) Silica

(b) Silica and alumina

(c) Silica, alumina and alkali

(d) Silica, alumina, alkali and iron

Answer: (a) Silica

Pozzolanas are rich in silica, which reacts with calcium hydroxide in cement to improve strength and durability.

3. Rapid setting cement contains relatively higher proportion of:

(a) C3S

(b) C2S

(c) C3A

(d) C4AF

Answer: (c) C3A

Rapid-setting cement contains a higher proportion of tricalcium aluminate (C3A), which accelerates the setting process.

4. For the manufacture of Portland cement, the proportions of raw material used are:

(a) Lime 63%; silica 22%; other ingredients 15%

(b) Silica 2%; lime 63%; other ingredients 15%

(c) Silica 40%; lime 40%; other ingredients 40%

(d) Silica 70%; lime 20%; other ingredients 20%

Answer: (a) Lime 63%; silica 22%; other ingredients 15%

In Portland cement manufacturing, lime makes up about 63% of the raw materials, while silica accounts for around 22%, with the remaining being other compounds.

5. Which IS code gives specification about cement plaster?

(a) IS 1500

(b) IS 1221

(c) IS 1400

(d) IS 1661

Answer: (d) IS 1661

The relevant IS code for cement plaster is IS 1661, which provides specifications for cement plastering.

6. In the process of hydration of OPC, to complete all chemical reactions, the water requirement (expressed as the percentage of cement) is _______.

(a) 5 to 8%

(b) 8 to 16%

(c) 20 to 25%

(d) 35 to 45%

Answer: (c) 20 to 25%

OPC requires 20-25% water by mass of cement for complete hydration during chemical reactions.

7. The type of cement used in lining of deep tube wells is:

(a) Blast furnace slag cement

(b) High alumina cement

(c) Oil well cement

(d) Portland pozzolana cement

Answer: (c) Oil well cement

Oil well cement is used for lining deep tube wells due to its resistance to high temperatures and pressure.

8. In concrete, Calcium sulphate may act as:

(a) An accelerator

(b) A retarder

(c) An air entraining agent

(d) An air detraining agent

Answer: (b) A retarder

Calcium sulphate acts as a retarder, slowing down the setting time of concrete.

9. Concrete is unsuitable for compaction by vibrator if it is:

(a) Dry

(b) Earth moist

(c) Semi-plastic

(d) Plastic

Answer: (d) Plastic

Concrete in a plastic state is unsuitable for compaction by a vibrator because it's too fluid, making vibration ineffective.

10. As per IS: 456-2000; the organic content of water used for making concrete should not be more than:

(a) 200 mg/l

(b) 250 mg/l

(c) 100 mg/l

(d) 150 mg/l

Answer: (a) 200 mg/l

According to IS: 456-2000, the organic content in water for making concrete should not exceed 200 mg/l.