Construction Materials and Management MCQ Quiz - Objective Question with Answer for Construction Materials and Management - Download Free PDF

Explanation:

Timber:

• Timber is sawn or milled wood used for engineering purposes like building, furniture and railway track wooden sleeper construction.

Classification of the tree:

For engineering purposes, the trees are classified according to their mode of growth.

(i) Endogenous tree:

• These trees grow inwards
• Timber from these trees has very limited engineering applications.
• Example of endogenous trees are bamboo, cane, palm etc.

(ii) Exogenous tree:

• These trees grow outwards, increasing in bulk with the formation of the ring every year.
• These annual rings are used for predicting the age of the tree.
• These trees are mostly used for engineering works.
• They are further divided as conifers and deciduous.

Conifers (Evergreen trees):

• The leaves of these trees do not fall till new ones are grown. These have needle-shaped leaves and bear cone-shaped fruits.
• These trees yield softwood (easily cut), which are generally light coloured, resinous, lightweight and weak
• They have distinct annual rings.
• Example: deodar, pine, fir and larch

Deciduous or board leaf trees:

• These trees have flat broad leaves. The leaves of these trees do not fall till new ones appear in the spring season.
• They do not show distinct annual rings.
• These trees yield hardwood, which is generally close-grained, strong, heavy, dark coloured, durable and nonresinous; and are used for engineering applications.
• Example: teak, mahogany, Sheesham, oak, sal, babool etc.

Important Points

(i) Hardwoods are used in engineering construction which are derived from deciduous trees, whereas conifers trees yield softwood which is used for other purposes like making sports equipment, paper etc.

(ii) The names hardwoods and softwoods are commercially popular but have nothing to do with the hardness of the particular group some softwoods like deodar are harder than hardwoods like papita.

Explanation: 
Types of surface finishes

1. Rock face or quarry faced finish
2. scabbling finish
3. hammer dressed finish
4. axed finish
5. punched finish
6. picked finish
7. boasted finish
8. tooled finish
9. furrowed finish
10. dragged or combed finish
11. Reticulated finish

• The stones are made roughly square or rectangular using Waller's hammer. the exposed faces are roughly shaped using a mash hammer. the bends and joints are dressed back some 75 to 100 mm from the face

• After having brought the face of the stone to a level and smooth finish, marginal drafts are sunk about 10 mm below the surface. This sinking are then worked to a depth equal to that of the drafts to cut winding snake-like (verminuos) ridges. the finish present warm eaten appearance.

• This is similar to Vermiculated except that the ridges or vein are less winding. These are linked up to form polygon or irregular shaped reticles.

• In this, the dressing is done with the help of a boaster and hammer forming a series of 38 to 50 mm wide bands of more or less parallel tool marks, which cover the whole surface. This mark may be horizontal vertical or inclined at 45°.

• This finish is used only in soft stones. The surface of the stone is first brought to the required level using a dumpy and soft stone chisel.
• Drags, made of steel plates and of different grades are then dragged backward and forward in different directions until the tool marks are eliminated. Fine drag is used at the end which eliminates all the scratches on the stone a combed finish is obtained

Explanation:

Types of brick masonry bonds:

Concept-

The usual defects which are found in the painting work are-

Blistering:

• This defect is caused by the water vapour which is trapped behind the painted surface. The formation of bubbles under the film of paint occurs in this defect. It may occur from various causes such as imperfect seasoning of timber, excess oil used in final coat etc.

Bloom:

• In this defect, the formation of dull patches occurs on the finished polished surface. It is due to the defect in paint or bad ventilation.

Fading:

• The gradual loss of colour is known as the fading and it is mainly due to the effect of sunlight on pigments of paint.

Flaking:

• A small portion of the painted surface is sometimes seen loose. It is known as the flaking and is due to poor adhesion.

Flashing:

• Sometimes the glossy patches are seen on the painted surface. This is known as the flashing and it is mainly due to poor workmanship, cheap paint or weather actions.

Grinning:

• When the final coat of paint has not sufficient opacity, the background is clearly seen. This is known as the grinning.

Running:

• The paint runs back and leaves small areas of surface uncovered. This defect occurs when the surface to be painted is too smooth.

Sagging:

• When a vertical or inclined surface is too thickly painted, the defect of sagging occurs.

Saponification:

• The formation of soap patches on the painted surface is termed as the saponification and it is due to chemical action of alkalies.

Wrinkling:

• When a horizontal surface is too thickly painted, the defect of wrinkling becomes prominent.

Explanation:

Diagonal Cracks:

• The crack follows a stair-step pattern, moving diagonally across the wall through the mortar joints, which is typical in brick masonry walls.

• Diagonal cracks like these are usually caused by foundation settlement, differential movement, or lateral loads such as seismic activity or soil pressure.

• These types of cracks are often signs of structural distress and should be carefully investigated to assess the extent of damage and required repair.

Additional Information

Here is some additional information related to diagonal cracks in brick masonry walls:

Causes:

1. Foundation Settlement: Uneven or differential settlement causes stress in the wall, leading to diagonal cracks.

2. Soil Movement: Expansive soils (like clay) swelling or shrinking due to moisture changes can shift the foundation.

3. Seismic Activity: Earthquakes can impose lateral forces that lead to diagonal shear cracks.

4. Lateral Loads: Wind or earth pressure on retaining walls may cause such cracks.

5. Poor Construction Practices: Lack of proper bonding, inadequate curing, or weak mortar may contribute.

Effects:

• Can lead to water seepage and reduced structural strength.

• May indicate serious underlying problems in foundation or soil.

Remedial Measures:

• Foundation strengthening (e.g., under-reamed piles, jacketing).

• Grouting or epoxy injection to seal cracks.

• Stitching technique using steel rods across the crack.

• Replacing or strengthening the affected masonry units.

Monitoring crack width and propagation over time is also a good practice to assess the severity.

Concept:

Fine aggregate:

The grading of fine aggregates, when determined as described in IS: 2386 (Part I)-1963 shall be within the limits given in Table 4 and shall be described as fine aggregates, Grading Zones I, II, III and IV: Where the grading falls outside the limits of any particular grading zone of sieves other than 600-micron IS Sieve by a total amount not exceeding 5 percent, it shall be regarded as falling within that grading zone. This tolerance shall not be applied to the percentage passing the 600-micron IS Sieve or to the percentage passing any other sieve size on the coarse limit ef Grading Zone I or the finer limit of Grading Zone IV.  

As per IS:383-1970:(Table 4)

The correct answer is slaked lime.

• Quicklime (CaO) reacts with water to form slaked lime {Ca(OH)₂}.
• The addition of a limited amount of water to quick lime is called slacking of lime.
• When Calcium oxide is mixed with water it forms Calcium Hydroxide.
• The above reaction can be written as
  • ⇒ CaO + H₂O → Ca(OH)₂
• Calcium Hydroxide is used in the preparation of Mortar.

Additional Information

1) Weathering is the process of breaking down and loosening the surface minerals of rock so that they can be transported away by agents of erosion such as water, wind and ice.

2) Quarrying is the multistage process by which rock is extracted from the ground and crushed to produce aggregate, which is then screened into the sizes required for immediate use, or for further processing, such as coating with bitumen to make bituminous macadam or asphalt.

3) Dressing of Stone is the working of quarried stone into the shape and size required for use. This can be necessary as stones obtained from quarrying generally do not have the exact required dimensions or finish.

Concept:

Impact test:

Impact test is used to determining the toughness of stone, it is performed in an Impact Test Machine as followed:

1. A cylinder of diameter 25mm and height 25mm is taken out from the sample of stones.
2. It is then placed on the cast iron anvil of the machine.
3. A steel hammer of weight 20N is allowed to fall axially in a vertical direction over the specimen.
4. The height of the first blow is 1 cm, that of the second blow is 2 cm, that of the third blow is 3 cm, and so on.
5. Blow at which specimen breaks is noted. If it is an nth blow, ‘n’ represents the toughness index of stone.

Explanation:

Slaking is the process in which quick lime reacts with water, during this reaction, it swells, cracks, and falls out as calcium hydroxide.

\(\underbrace {CaO}_{\begin{array}{*{20}{c}} {Quick} \\ {lime} \end{array}} + {H_2}O\xrightarrow{{Slaking}}\underbrace {Ca{{\left( {OH} \right)}_2}}_{\begin{array}{*{20}{c}} {Hydrate} \\ {lime} \end{array}} + Heat\)

Concept:

Classification and uses of building stones-

A good building stone has the following properties:

• Percentage of wear in the attrition test should not be more than 3
• Specific gravity should be at least 2.7
• Coefficient of hardness should be greater than 17
• Percentage of water absorption by weight of stone should be less than 5
• Toughness index should not be less than 13
• Crushing strength should be greater than 100 N/mm² or MPa.

Explanation:

Fineness modulus of sand (fine aggregate) is an index number that represents the mean size of the particles in sand.

FM is the sum of the total percentages retained on each specified sieve divided by 100.

Explanation:

Standard consistency test:

• This test determines the percentage of water required to make workable cement paste.
• Vicat’s apparatus is used to perform this test.
• Temperature during test = 27 ± 2°C
• Relative humidity = 90%
• As per Vicat’s test ‘the percentage of water added to the cement at which the needle can not penetrate 5-7 mm from bottom of the mould is called consistency.
• For OPC consistency is around 30%
• In order to make a cement paste of normal consistency, the percentage of water varies from 25 to 35%.

Important Points

A good building stone has the following properties:

• The percentage of wear in the attrition test should not be more than 2 for road work.
• Specific gravity should be at least 2.7
• The coefficient of hardness should be greater than 17
• Percentage of water absorption by weight of stone should be less than 5
• The toughness index should not be less than 13
• Crushing strength should be greater than 100 N/mm²

For road works, Wear not more than 2% and for building stone, It should not more than 3%.