SSC-Junior Engineer (Civil & Structural) Online Exam 2018 (Part-IV)

Total Questions: 50

1. Aerated concrete is _________ in weight.

Correct Answer: B. light
Solution:Aerated Concrete: Lightweight concrete in which the lightness is obtained by the formation of macroscopic gas bubbles mainly by chemical reaction within the mass during the liquid or plastic phase.

The air bubbles are uniformly distributed and are retained in the matrix on setting and hardening to produce a cellular structure.

2. In gauge pressure, the atmospheric pressure on the scale is marked as:

Correct Answer: A. 0
Solution:Gauge pressure is defined as the pressure, which is measured with the help of a pressure measuring instrument, in which, the atmospheric pressure is taken as a datum. The atmospheric pressure on the scale is marked as zero.

Mathematically,

Absolute Pressure = Atmospheric Pressure + Gauge Pressure
Vacuum Pressure = Atmospheric Pressure - Gauge Pressure

3. Glacier deposited soil is called:

Correct Answer: C. till
Solution:Glaciers deposited materials in many ways, so there are several kinds of glacial drift. During the melting process, some debris simply dropped in place to form deposits called glacial till. Some till dropped at the margins of the glacier, forming hills called moraines.

Other kinds of till were deposited beneath advancing ice; these materials, crushed under the weight of the ice riding over them, are often extremely dense and compacted. In some areas such as parts of New England and Minnesota, they form dense hardpans. Because there was no sorting action in the deposition, glacial till is extremely variable, and so are the soils derived from it. Till soils often contain pebbles, stones, and even boulders.

4. An error due to the earth's curvature and refraction is to be corrected using:

Correct Answer: C. C꜀ = 0.0673 D²
Solution:Curvative Correction: For long sights, the curvature of earth affects staff readings. The line of sight is horizontal, but the level line is curved and parallel to the mean spheroidal surface of the earth. The vertical distance between the line of sight and the level line at a perpendicular plane is called the curvature correction. Due to curvature, objects appear lower than what they really are.

Curvature Correction,
c꜀ = D²/2R = 0.0785 D² m (-)
where, D = Horizontal distance in kilometres.
R = Radius of earth.

Refrection Correction: When long sights are taken, the line of sight is refracted through layers of air of varying density towards the surface of the earth in a curved path. Due to the effect of refraction, objects appear higher than what they really are:

Refraction correction
cᵣ = 1/7 × D²/2R
= 0.0112 D² m (+)

Combined Correction:
Combined correction
= Curvature correction + refraction correction
= -0.0785 D² + 0.0112 D²
= -0.0673 D² m (subtractive).

5. Estimate the quantity of plastering (two faces) for 4 m long, 3 m high and 30 cm thick wall.

Correct Answer: B. 24 sqm
Solution:Since, plastering will be done on both sides of wall or two faces.

Hence, quantity of plastering work
= 2 x (length of wall × height of wall)

  • Length of wall = 4 m
  • Height of wall = 3 m
  • Thickness of wall = 30 cm

So, quantity of plastering work = 2 (4 × 3)
[Quantity of plastering work = 24 m²].

6. For big work or projects, the percentage estimated cost provided in the estimate for the purchase of tools and plants is:

Correct Answer: D. 1 to 1.5%
Solution: Tools and Plant (T & P): For the execution of big works, provision for the purchase of machinery etc. For big projects an amount 1% to 1.5% of the estimated cost is also provided to purchase special tools and plants for specific purposes.

Contingency Fund: This estimated cost is increased by 3% to 5% for all unforeseen expenditure.

Note: The commission has rejected the question in revised answer key.

7. Good brick earth should contain __________ of Alumina.

Correct Answer: Α. 20% - 30%
Solution:The constituents of good brick earth are:

1. Alumina: A good brick earth should contain 20-30 per cent of alumina. It imparts the property of plasticity to the earth. An excess of alumina causes shrinkage and warping of bricks during drying and burning and it becomes too hard when burnt.

2. Silica: Silica forms 50-60 per cent of good brick earth. It is seen either in the free or combined state. In the free state, it is mechanically mixed with clay and in the combined form it exists in a chemical composition with alumina. The cracking, shrinking and warping of raw bricks are being prevented by the presence of silica. The durability of bricks depends upon the proportion of silica. An excess of silica destroys the cohesion between particles and the bricks become brittle.

3. Lime: A good brick earth should contain lime not exceeding 5 per cent. It should be present in a very finely powdered state in order to prevent the flaking of bricks. Lime prevents the shrinkage of bricks. An excess of lime causes the bricks to melt and, hence, to lose its shape.

4. Oxides of iron: A small quantity of the oxide of iron to the extent of 5-6 per cent is desirable in good brick earth. It imparts red colour to the bricks. But excess of lime makes the colour dark blue or blackish. On the other hand, if the quantity of lime is less, the bricks will be yellowish in colour. It also helps to fuse sand and, thereby, increases the hardness of bricks.

5. Magnesia: Presence of magnesia in small quantity imparts a yellowish tint to the bricks and decreases the shrinkage. But if in excess, it causes the decay of bricks.

8. The unit of measurement is square metres in case of:

Correct Answer: C. pointing work
Solution:The methods and units of measurements for civil construction works are mainly categorised for their nature, shape and size and for making payments to the contractor. The principle of units of measurements normally consists the following:

(a) Single units work like doors, windows, trusses etc., are expressed in numbers.

(b) Works consists linear measurements involve length like cornice, fencing, hand rail, bands of specified width etc., are expressed in running metres (RM).

(c) Works consists a real surface measurements involve area like plastering, white washing, partitions of specified thickness etc., and are expressed in square meters (m²)

9. Water absorption for class A type of roof tiles is:

Correct Answer: D. 20% - 24%
Solution:Roofing tiles are generally have thinner sections as compared to bricks and therefore require better care and attention at all stages of manufacture.

As per IS 654-1972

  • Water absorption for class A type of roofing tiles are 20-24% and average breaking load 68 kg/cm² .
  • Water absorption for class AA type of roofing tiles are 9-10% and average breaking load 102 kg/cm² .

10. The process by which timber is cut and sawn into sections is called:

Correct Answer: A. conversion of timber
Solution:Conversion is the process of cutting boles or logs into sections prior to seasoning. Subsequent further cutting into usable sizes is called manufacture. Finishing operations, involving planing and sanding, produce a visually smooth surface but reduce the absorption of penetrating wood stains.

Timber for solid sections is sawn, whereas thin layers for plywood are peeled and veneers are usually sliced across the face of the log to maximise the visual effect of colour and figure, which is the pattern effect seen on the longitudinal surface of cut wood.