SSC-JUNIOR ENGINEER (Civil & Structural) Online Exam 2016

Paper-I

Total Questions: 50

1. The standard size of brick as per Indian standard is _________.

Correct Answer: C. 19 cm × 9 cm × 9 cm
Solution:Bricks are prepared in various sizes. If the bricks are too large, it is difficult to burn them and handle them. But, if the bricks are small, more quantity of mortar is required while placing. In India, the standard size recommended by the Bureau of Indian Standards (BIS) is 19 cm × 9 cm × 9 cm and the size of a brick including the mortar thickness is 20 cm × 10 cm × 10 cm, which is known as the nominal size of the brick.

2. The quick lime as it comes from kiln is called:

Correct Answer: C. Lump lime
Solution:Quick Lime: The lime obtained from the calcination of pure lime stone is known as quick lime. Quick lime has great affinity for moisture. It is essentially calcium oxide, but some times small amount of magnesium oxide (MgO) may be present along with calcium oxide (CaO). Quick lime is also known as Caustic lime. The quick lime as it comes out from kilns is known as lump lime.

3. How does the seasoning of timber help?

 

(a) It increases the weight of timber

(b) It improves the strength properties of timber

Correct Answer: B. Only (b)
Solution:Seasoning of Timber

Seasoning of timber is the process of drying timber or removing moisture or sap, present in a freshly felled timber, under more or less controlled conditions.

Freshly felled timber contains a large quantity of moisture roughly from 100 to 200%, based on dry weight of wood. A well seasoned piece of wood may contain about 10 to 12% moisture and will be in equilibrium with atmospheric humidity of a particular place.

If the timber is used without seasoning, it is liable to shrink, warp and crack, if used, it may even rot and decay. Thus all timbers should be used after proper seasoning.

Seasoning should be the first step for the efficient utilization of timber.

Advantages of seasoning:

Following are the advantages of seasoning timber:

1. Seasoning makes the timber less liable to attack by insects and fungus.

2. It decreases the weight of timber and makes it lighter.

3. It enables timber to be easily painted, polished and preserved.

4. It avoids defects appearing in timber during its use.

5. It improves the strength properties of the timber and makes it more stable.

6. It improves working qualities of timber.

7. It provides dimensional stability and retention to shape to the timber used in carpentry or joinery.

8. Seasoning increases the power in timber to hold metal fasteners.

4. The ductility value of bitumen is __________.

Correct Answer: C. Less than that of tar
Solution:The ductility test gives a measure of adhesive property of bitumen and its ability to stretch. Ductility is the property of bitumen that permits it to undergo great deformation or elongation. Ductility is defined as the distance in cm, to which a standard sample or briquette of the material will be elongated without breaking. Ductility value of bitumen is less than tar.

In flexible pavement design, it is necessary that binder should form a thin ductile film around aggregates so that physical interlocking of the aggregates is improved. Binder material having insufficient ductility gets cracked when subjected to repeated traffic loads and it provides pervious pavement surface.

Ductility of a bituminous material is measured by the distance in centimetres to which it will elongate before breaking when two ends of standard briquette specimen of material are pulled apart at a specified speed and specified temperature.

5. The penetration test on bitumen is used for determining its ________.

Correct Answer: A. Grade
Solution:To examine the consistency of a sample of bitumen by determining the distance in tenths of a millimetre that a standard needle vertically penetrates the bitumen specimen under known conditions of loading, time and temperature.

Penetration test is one of the most common conventional tests, it is used to classify the bitumen to grades. Penetration value is normally used as the grade of the bitumen. This test conducts for the 3 types of bitumen to specify the grade of each type.

The harder the bitumen, the higher penetration value will be shown up in this test. The sample is melted and cooled under controlled conditions. The penetration is measured with a penetrometer by means of which a standard needle is applied to the bitumen specimen under specific conditions.

6. Quartzite is a ________.

Correct Answer: B. Siliceous rock
Solution:Siliceous rocks are sedimentary rocks that have silica (SiO₂) as the principal constituent. In these rocks the principal component is quartz in fragments of greater or less size, either angular, or more or less rounded by wear. There are two major types of quartzite, based on genesis.

Orthoquartzite is a sedimentary rock composed largely of quartz sand cemented by nearly pure silica. Metaquartzite is a metamorphosed sandstone characterized by peripheral growth of recrystallized quartz. Both types fracture across the quartz grains and both fracture conchoidally, making good knapping material.

7. Plaster of Paris can be obtained from the calcination of ________.

Correct Answer: B. Gypsum
Solution:Gypsum must be calcined to produce plaster of Paris and kindred products. The chemical reaction is as follows:

2CaSO₄ → (CaSO₄) ₂H₂O + 3H₂O

To obtain plaster of Paris, the gypsum is calcined in open kettles at a temperature of 113 to 120 degrees C (235 to 250 degrees F), whereas hydrocal is obtained by calcining the gypsum in a closed kettle under a steam pressure of 17 pounds per square inch gage pressure, and a temperature of 123 degrees C (253 degrees F). Plaster of Paris is the hemihydrate of gypsum [(CaSO₄)₂H₂O].

The plaster first goes into solution to saturation. The following chemical reaction then takes place:

(CaSO₄)₂H₂O + ₃H₂O →2 CaSO₄ . ₂H₂O + 3900 calories per gram. The  gypsum formed, being less soluble than the plaster, is supersaturated in solution, and it therefore precipitates.

8. A brick masonry could fail due to _________.

Correct Answer: D. Any of these
Solution:No explanation given in the book

9. Which of the following statements is correct?

Correct Answer: B. Excess of alumina in the clay makes the brick crack and warp on drying.
Solution:Alumina: Alumina is a compound of aluminium oxide occuring naturally with earth. It gives plasticity to the earth so that moulding is possible. About 20-30 per cent of alumina is desirable in good earth. Excess of alumina makes raw bricks shrink and warp during drying and burning.

10. The compressive strength of 100 mm cube as compared to 150 mm cube is always ________.

Correct Answer: B. more
Solution:As per Indian Standards 150 mm cubes are used for determining the compressive strength of concrete. Use of 100 mm cubes has its advantages. The 100 mm cubes are easier to handle and will result in saving of materials, curing space, storage and labour. The overall savings can be significant in financial terms.