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

Explanation:

• A plunging fold as one where the fold axis is inclined (not horizontal).

• This results in:

  • Outcrop patterns that appear curved or V-shaped on geological maps.

  • A distinct difference from horizontal folds, which produce straight bands.

• Plunging folds often form due to complex tectonic stress, especially during multi-phase deformation.

• Symmetrical limbs or steep axial planes are not exclusive features of plunging folds.

Explanation:

• A normal fault is defined as a type of dip-slip fault where:

  • The hanging wall (block above the fault) moves downward.

  • The footwall (block below the fault) stays in place or moves upward.

• This occurs due to tensional forces, causing the crust to stretch and thin.

• Normal faults are commonly found in rift zones and extensional tectonic settings.

• Compressional stress leads to reverse or thrust faults, not normal faults.

Explanation:

• Joints are natural fractures in rocks without displacement, distinct from faults.

  • Spacing (distance between joints) and orientation (angle and direction) significantly influence:

    • Rock stability, especially in excavations, slopes, and foundations.

    • Water seepage and erosion patterns.

• Closely spaced joints reduce the block size and can increase the risk of failure under load.

• Mineral composition and color matter less in structural stability than joint geometry.

• While weathering degrades strength, joint properties directly govern structural behavior.

Explanation:

• Plasticity refers to the soil’s ability to undergo deformation without cracking or breaking.

• As per the textbook:

  • It is largely dependent on the amount and type of clay minerals present.

  • Montmorillonite, for example, has high plasticity, while kaolinite has lower plasticity.

• Clay minerals have a high surface area and adsorb water, allowing them to exhibit plastic behavior.

• Silt and sand lack cohesion and exhibit little to no plasticity.

• Organic matter may affect compressibility but not plasticity directly.

Explanation:

• Capillary action is the ability of soil to draw water upward from the water table into the unsaturated zone.

• It occurs due to:

  • Adhesive forces between water molecules and soil particles.

  • Surface tension pulling water into fine pores.

• Finer soils like clay and silt exhibit greater capillary rise due to smaller pores.

• The textbook emphasizes that this process plays a crucial role in:

  • Moisture availability for plants.

  • Corrosion risk in shallow foundations and underground structures.

• Gravity causes downward flow, not upward; pressure gradient drives saturated flow, not capillarity.

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%.