Concrete Technology

JKSSB Junior Engineer (Civil) · RCC Structures · 28 practice questions with answers and explanations: 18 Easy, 9 Medium, 1 Hard.

Sample questions

Sample Easy question 1

The compressive strength of concrete cubes is normally tested at an age of:

  1. 7 days
  2. 28 days
  3. 14 days
  4. 56 days
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Answer: B. Characteristic strength is defined at 28 days.

Sample Easy question 2

Increasing the water-cement ratio of a concrete mix generally:

  1. Does not change its strength
  2. Reduces its strength
  3. Increases its strength
  4. Increases its density
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Answer: B. More water leaves more voids, and strength falls (Abrams' law).

Sample Easy question 3

The workability of fresh concrete is commonly measured by the:

  1. Cube test
  2. Los Angeles test
  3. Soundness test
  4. Slump test
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Answer: D. The compaction factor and Vee-Bee tests are also used.

Sample Medium question 4

The modulus of elasticity of M30 concrete according to IS 456 is about:

  1. 27,386 N/mm²
  2. 15,000 N/mm²
  3. 30,000 N/mm²
  4. 5,477 N/mm²
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Answer: A. Ec = 5000√fck = 5000 × √30 = 27,386 N/mm².

Sample Medium question 5

The flexural tensile strength of M25 concrete is:

  1. 3.5 N/mm²
  2. 5.0 N/mm²
  3. 7.0 N/mm²
  4. 1.75 N/mm²
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Answer: A. fcr = 0.7√fck = 0.7 × 5 = 3.5 N/mm².

Sample Medium question 6

The 28-day compressive strength of 53 grade ordinary Portland cement mortar should be at least:

  1. 33 MPa
  2. 28 MPa
  3. 53 MPa
  4. 43 MPa
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Answer: C. The grade of cement is its minimum 28-day strength in MPa.

Sample Hard question 7

The cumulative percentages retained on the standard sieves for a sand are 2, 12, 30, 52, 75, 93. The fineness modulus is:

  1. 1.32
  2. 26.4
  3. 2.64
  4. 264
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Answer: C. FM = sum of cumulative percentages retained ÷ 100 = 264 ÷ 100 = 2.64.

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