Concrete Technology and Design

71. For a simply supported beam of span 15 m, the minimum effective depth to satisfy the vertical deflection limits should be

  1. 600 mm
  2. 750 mm
  3. 900 mm
  4. More than 1 m

Correct answer: (B)
750 mm

72. For a slab supported on its four edges with corners held down and loaded uniformly, the Marcus correction factor to the moments obtained by Grashoff Rankine's theory

  1. Is always less than 1
  2. Is always greater than 1
  3. Can be more than 1
  4. Can be less than 1

Correct answer: (A)
Is always less than 1

73. For an ordinary Portland cement

  1. Residual does not exceed 10% when sieved through IS Sieve No. 9
  2. Soundness varies from 5 to 10 mm
  3. Initial setting time is not less than 30 minutes
  4. Compressive stress after 7 days, is not less than 175 kg/cm2

Correct answer: (C)
Initial setting time is not less than 30 minutes

74. For batching 1:3:6 concrete mix by volume, the ingredients required per bag of 50 kg cement, are:

  1. 70 litres of sand and 120 litres of aggregates
  2. 70 kg of sand and 140 litres of aggregates
  3. 105 litres of sand and 140 litres of aggregates
  4. 105 litres of sand and 210 litres of aggregates

Correct answer: (D)
105 litres of sand and 210 litres of aggregates

75. For compacting plain concrete road surface of thickness less than 20 cm, we use

  1. Internal vibrator
  2. Screed vibrator
  3. Form vibrator
  4. None of these

Correct answer: (B)
Screed vibrator

76. For concreting of heavily reinforced sections without vibration, the workability of concrete expressed as compacting factor should be

  1. 0.75 - 0.80
  2. 0.80 - 0.85
  3. 0.85 - 0.92
  4. Above 0.92

Correct answer: (D)
Above 0.92

77. For concreting tunnel linings, transportation of concrete is done by

  1. Pans
  2. Wheel borrows
  3. Containers
  4. Pumps

Correct answer: (D)
Pumps

78. For construction of structures in sea water, the cement generally preferred to, is

  1. Portland-pozzolana cement
  2. Quick setting cement
  3. Low heat Portland cement
  4. Rapid hardening cement

Correct answer: (A)
Portland-pozzolana cement

79. For ensuring quality of concrete, use

  1. Single sized aggregates
  2. Two sized aggregate
  3. Graded aggregates
  4. Coarse aggregates

Correct answer: (C)
Graded aggregates

80. For given water content, workability decreases if the concrete aggregates contain an excess of

  1. Thin particles
  2. Flat particles
  3. Elongated particles
  4. All the above

Correct answer: (D)
All the above

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