D68 MASTER THE DAY

Which property of steel ensures good bond with concrete?

• High thermal conductivity
• Similar coefficient of thermal expansion as concrete
• High density
• Low modulus of elasticity

Answer explanation

Matching thermal expansion with concrete prevents bond failure due to temperature changes.

Clear cover at the end of bars should be at least:

• 50 mm
• 15 mm
• 40 mm
• Twice the diameter of bar or 25 mm, whichever is greater

Answer explanation

Minimum clear cover at bar ends is 2× bar dia, but not less than 25 mm.

The unit weight of steel is taken as:

• 78.5 kN/m³
• 24.4 kN/m³
• 100 kN/m³
• 50 kN/m³

Answer explanation

Unit weight of steel is 78.5 kN/m³ or 7850 kg/m³.

Purpose of steel in RCC is to resist:

• Tensile stresses
• Shear stresses only
• Compressive stresses
• All stresses equally

Answer explanation

Steel reinforcement primarily resists tensile stresses in RCC.

Which type of bar shape is represented by 'U-bar'?

• A bar bent into a U shape for anchorage
• A straight bar
• A bar bent into an L shape
• Circular ring

Answer explanation

U-bars are bent into a 'U' shape to improve anchorage in concrete.

The standard 135° hook requires an extension of:

• 12d
• 8d
• 10d
• 9d

Answer explanation

A 135° hook requires 10 times the bar diameter as extension.

The excess length for cranked bars is provided to:

• Maintain slope at supports
• Reduce concrete usage
• Increase bond strength
• Prevent cracking at center

Answer explanation

Cranked bars have extra length to maintain slope and development length near supports.

BBS preparation helps in:

• Reducing curing period
• Replacing reinforcement
• Reducing wastage of steel
• Increasing concrete grade

Answer explanation

Bar Bending Schedule helps in reducing wastage and controlling steel usage.

Which IS code is for RCC design and construction?

• IS 875
• IS 10262
• IS 456
• IS 800

Answer explanation

IS 456 is the code for Plain and Reinforced Concrete design and construction.

Which factor helps prevent theft of steel at site?

• Reducing bar diameter
• Increasing concrete cover
• Painting bars
• Accurate BBS and stock control

Answer explanation

BBS and stock control reduce theft and pilferage of steel.