6. Work ability of concrete can be measured using slump, compaction factor and Vebe time. Consider the following statements for work ability of concrete:
   (i) As the slump increases, the Vebe time increases
   (ii) As the slump increases, the compaction factor increases
   Which of the following is TRUE?

1. 1. Both (i) and (ii) are True

   
   
   

   2. Both (i) and (ii) are False

   
   
   

   3. (i) is True and (ii) is False

   
   
   

   4. (i) is False and (ii) is True

   
   
   

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   As slump increases, Vebe time increases.

   Correct Option: D

   As slump increases, Vebe time increases.

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7. The modulus of elasticity, E = 5000 √f_ck where f_ck is the characteristic compressive strength of concrete, specified in IS: 456-2000 is based on

1. 1. tangent modulus

   
   
   

   2. initial tangent modules

   
   
   

   3. secant modulus

   
   
   

   4. chord modulus

   
   
   

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1. View Hint View Answer Discuss in Forum

   initial tangent modules

   Correct Option: B

   initial tangent modules

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8. Consider the singly reinforced beam shown in the figure below:
   
   At cross-section XX, which of the following statements is TRUE at the limit state?

1. 1. The variation of stress is linear and that of strain is non-linear

   
   
   

   2. The variation of strain is linear and that of stress is non-linear

   
   
   

   3. The variations of both stress and strain is linear

   
   
   

   4. The variation of both stress and strain is non-linear

   
   
   

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   Correct Option: B

   

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9. A concrete column caries an axial laod of 450 kN and a bending moment of 60 kM m at its base. An isolated footing of size 2m by 3m, with 3m side along the plane of the bending moment, is provided under the column. Centres of gravity of column and footing coincide. The net maximum and the minimum pressures in kN/m² on soil under the footing are respectively.

1. 1. 95 and 55

   
   
   

   2. 95 and 75

   
   
   

   3. 75 and 55

   
   
   

   4. 75 and 75

   
   
   

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1. View Hint View Answer Discuss in Forum

   Pressure due to load
   

   =	P	=	450	= 75 kN/m2
   	A		2 × 3

   
   Stress at extreme fibre (due to moment) = M/z
   

   =	M	× y
   	I

   
   
   = 20 kN/m²
   σ_max = 75 + 20 = 95 kN/m²
   σ_min = 75 – 20 = 55 kN/m²

   Correct Option: A

   Pressure due to load
   

   =	P	=	450	= 75 kN/m2
   	A		2 × 3

   
   Stress at extreme fibre (due to moment) = M/z
   

   =	M	× y
   	I

   
   
   = 20 kN/m²
   σ_max = 75 + 20 = 95 kN/m²
   σ_min = 75 – 20 = 55 kN/m²

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10. Consider the following statements for air-untrained concrete:
    (i) Air-entertainment reduces the water demand for a given level of work ability
    (ii) Use of air-untrained concrete is required in environments where cyclic freezing and thawing is expected
    Which of the following is TRUE?

1. 1. Both (i) and (ii) are True

   
   
   

   2. Both (i) and (ii) are False

   
   
   

   3. (i) is True and (ii) is False

   
   
   

   4. (i) is False and (ii) is True

   
   
   

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   Both statements are true

   Correct Option: A

   Both statements are true

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