Important 1000 MCQ For CIVIL Junior Engineer : Part 5

Important 1000 MCQ For CIVIL Junior Engineer

50. In order to have segregation in concrete dropping height should not be more than ______.
A. 25 cm. B. 50 cm
C. 100 cm. D. 250 cm

Correct Ans. C

Solution

  • The concrete shall be deposited as nearly as practicable in its final position to avoid rehandling. The concrete shall be placed and compacted before initial setting of concrete commences and should not be subsequently disturbed. Methods of placing should be such as to preclude segregation. Care should be taken to avoid displacement of reinforcement or movement of formwork. As a general guidance, the maximum permissible free fall of concrete may be taken as 1.5 m. Theoretically for drop placing it should not be more than 1 to 1.5 meter for well cohesively mixed concrete.

51. For protection from frost, concrete
should be _______.

A. Dense
B. Free from cracks
C. Adhesion between mortar and
aggregate should be perfect
D. All the options are correct

Correct Ans. D

Solution:

  • When frosting occurs on the concrete then seepage in concrete starts which decreases the strength of the concrete. So that’s why for protection Concrete should be dense. Capturing the early heat of hydration will help maintain the cure temperature but will also help to promote hydration which in turn produces additional heat. Be sure to protect corners and surfaces since these areas are the most susceptible to early-age freezing and damage. Mainly, protect the concrete from early-age freezing, protect to ensure adequate strength gain, and protect from thermal shock and cracking.

52. A concrete in which dry coarse
aggregate are first packed to have the
least voids and then the cement sand
mortar is injected under pressure to
fill all the voids, resulting in a very
dense concrete, is known as ______.

A. Pre packet concrete

B. Vacuum concrete
C. No fines concrete
D. Aerate concrete

Correct Ans. D

Solution.

  • if a concrete has voids then we can fill these voids by injected the cement sand mortar. This process is known as aerate concrete. It is used in floor construction & in fire proofing because it have good fire resistivity.

53. Which one of the following properties of a plastic concrete is modified by the air entraining agents?

A. workability
B. segregation
C. bleeding
D. All option are correct

Correct Ans. D

Solution:

  • if we add the air entraining agent to the concrete or if we add the, Al (aluminium) powder to the concrete, then air bubble is formed which increases the workability of concrete & decreases the segregation (it seperate coarse particle from the water) & bleeding (it seperate water from the coarse particle) in concrete.

Important 1000 MCQ For CIVIL Junior Engineer : Part 4

54. Approximate value of shrinkage strain in concrete is ______.

A. 0.03 B. 0.003
C. 0.0003 D. 0.00003

Correct Ans. C

Solution.

  • As per clause 6.2.4.1 of IS 456:2000, In the absence of test data, the approximate value of the total shrinkage strain for design may be taken as 0.0003.

55. Shrinkage of concrete is directly
proportional to ______.

A. Cement content
B. Sand content
C. Aggregate content
D. Temperature of water

Correct Ans. A

Solution.

  • The drying shrinkage increases with an increase in cement content or an increase in water content. Shrinkage is greater with richer mixes (more of cement) and also with aluminous cements. Other things being equal, shrinkage of concrete is almost directly proportional to the amount of water in the mix. The type of aggregate used does not generally affect the shrinkage seriously though it has an indirect effect due to the difference of water/cement ratio depending on the type of the aggregate; with the large size of aggregate shrinkage is low.

56. Slump test is a measure of ______.

A. Tensile strength

B. Compressive strength
C. Impact value
D. Consistency

Correct Ans. D

Solution.

  • The concrete slump test measures the consistency of fresh concrete before it sets. It is performed to check the workability of freshly made concrete, and therefore the ease with which concrete flows. It can also be used as an indicator of an improperly mixed batch.

57. The durability of concrete is affected
by ______.

A. Cider
B. Vinegar
C. Alcohol
D. Both cider and vinegar

Correct Ans. D

Solution.

  • both the cider & vinegar is alcoholic beverage. If we mix these two in mixing of concrete, then it decreases the strength of concrete & durability of concrete.

58. Segregation is responsible for
______.

A. Honey comb concrete
B. Porous layers in concrete
C. Sand streaks in concrete
D. All the options are correct

Correct Ans. D

Solution.

  • When concrete beaks into the part then some types of structure of concrete is formed due to segregation like, Honey comb concrete, porous concrete, & sand streaks.

Important 1000 MCQ For CIVIL Junior Engineer : Part 1

59. If the slump of concrete mix is 60 mm its workability is ______.

A. Low B. Medium
C. High D. Very high

Correct Ans. B

Solution.

60. Strength of concrete show an
increase with ______.

A. Decrease in rate of loading
B. Increase in rate of loading
C. Unaffected by rate of loading
D. Depends on application of load

Correct Ans. B

Solution:

  • Strength of concrete = (load at the failure)/(area of the specimen of the concrete) So, if we increase the rate of loading gradually then it’s strength also will increase.

61. Two beam of equal cross sectional
area are subject to equal bending
moment. If one beam has square
cross section and the other has
circular section, then ______.

A. both beams will be equally strong
B. circular section beam will be
stronger
C. square section beam will be
stronger
D. the strength of the beam will
depend on the nature of aiding

Correct Ans. C

Solution:

  • From the bending equation, M/I = σ/y

M = σ × Z

  • So, σ is inversely proportional to I.
  • If I or Z will be more then beam will be stronger. & here I will be more for the square cross-section.

62. A closed coil helical spring is
subjected to a torque about its axis.
The spring wire would experience a
_______.

A. Bending stress
B. Direct tensile stress of uniform
intensity at its cross section
C. Direct shear stress
D. Torsional shearing stress

Correct Ans. D
Solution.

  • When an axial load is applied to the spring, stresses are developed due to Torsion, Direct Shear due to axial load and bending stresses. The stresses due to the direct shear and bending are very small and may be neglected in comparison to the torsion. And for light springs direct shear also can be neglected. Hence, finally shear stress due to torsion dominates which is given by 16T/∏d3

63. The maximum shear stress occurs on the outermost fibres of a circular
shaft under torsion. In a close coiled
helical spring, the maximum shear
stress occurs on the _______.A. Outermost fibers
B. Fibers at mean diameter
C. Innermost fibers
D. None of these

Correct Ans. C
Solution.

  • Maximum shear stress occur at the inner end of the spring

Note : d/4R counts for direct shear.
Hence, In case of closed coil helical
spring, the maximum shear occurs on
the innermost fibres.

Important 1000 MCQ For CIVIL Junior Engineer : Part 3

64. The core of a circular section short
column of diameter d is a concentric
circular area having a diameter ______.

A. d/4 B. d/3
C. d/2 D. d/8

Correct Ans. A

Solution:

Core area of a circular section short
column = ∏d2 /64
The circular area of diameter d’ =∏d’2/4
So, for concentric d’= d/4

65. If a close coiled helical spring absorbs 30 Nmm of energy while extending by 5mm, its stiffness will be _____.

A. 2.4 N/mm. B. 4.8 N/mm
C. 6 N/mm. D. 10 N/mm

Correct Ans. A

Solution.

  • U = 0.5 × P × Deflection (=work done)

30 Nmm = 0.5 × P × 5mm
P = 12 N
Stifness, K = P/Deflection
= 12N/5mm
= 2.4 N/mm

66. Which of the following sections will be best in torsion?

A. Solid circular
B. Hollow circular
C. Triangular
D. Rectangular

Correct Ans. B
Solution.

  • Circular tubes/Hollow shafts are more efficient than solid shafts in resisting torsional loads. As in typical hollow shaft, most of the material is near the outer boundary of the cross-section. Thus, if weight reduction and savings of materials are important, it is advisable to use hollow shafts.

67. A rectangular bar has been subjected
to torsion. The maximum shear stress
will occur _______.

A. At the centre
B. At the corner
C. At the middle of longer side
D. Along the diagonal

Correct Ans. C

Solution.

  • Schematic of shear stress distribution in a bar with solid rectangular cross section subjected to end torsion. The shear stress is maximum on the boundary and zero at the centre of the rectangle.

68. A support is said to be non yielding if
______.

A. It can take any type of reaction
B. It is frictionless
C. settlement occurs
D. The beam has zero slope at the
support

Correct Ans. D

Solution.

  • Fixed support is also known as non- yielding support.

69. The maximum bending stress in an I
beam occurs at the _______.

A. Neutral axis
B. Outermost fiber
C. Joint of wedge and flange
D. Section where shear stress is
maximum

Correct Ans. B

Solution:

  • by the equation, M/I = σ/y
  • In I section the outermost fibre have large area. & less moment of inertia. So, max. bending stress occurs at the outermost fibre.

70. A torsion member is fabricated from
two concentric thin tubes. At the
ends, the tubes are welded to rigid
discs so that both the tubes are
twisted as a unit. The radius of the
outer tube is 2r and that of the inner
tube is r. If the shear stresses
developed in the outer tube is ‘τ’, then
the shear stress in the inner tube will
be ______.
A. τ B. 0.25 τ
C. 0.75 τ D. 0.5 τ

Correct Ans. D

Solution:

  • from the torsional equation T is directly proportional to r
  • So, T1(Shear Stress at the inner surface)/T2(Shear Stress at the inner surface) = r1/r2

T1/T = r/2r = 0.5
So, T1 = 5T = 0.5

Important 1000 MCQ For CIVIL Junior Engineer : Part 2