Civil war-Day 24-LSGD-RCC BASICS

Under water concreting is done at a temperature of :

• 2°C
• 3°C
• 4°C
• 5°C

Answer explanation

A minimum of about 5°C is recommended to ensure workable, non-freezing conditions underwater.

How much yield stress does a twisted bar have more than an ordinary mild steel bar?

• 50%
• 10%
• 20%
• 30%

Answer explanation

twisted bar have 50% more yield stress than ordinary mild steel bar

Diameter of mild steel bars is expressed in

• mm
• cm
• cm2
• None

Answer explanation

Rebar diameters are specified in millimetres (e.g., 8, 10, 12, 16, 20 mm).

The unit weight of steel for RCC

• 1000 kg
• 7850 kg
• 785 kg
• 1001 kg

Answer explanation

Steel density ≈ 7850 kg/m³; this value is used for RCC calculations.

Which is the maximum size of coarse aggregate for a mix of M20 concrete ?

• 40 mm
• 20 mm
• 12.5 mm
• 10 mm

Answer explanation

For general RCC in M20, 20 mm nominal maximum size aggregate is commonly specified.

A reinforced concrete beam is assumed to be made of

• homogeneous material
• heterogeneous material
• isotropic material
• none of the above

Answer explanation

A reinforced concrete beam is assumed to be made of heterogeneous material

The concrete as per BIS 456 – 1978 is designated in ______ grades namely M15, M20 etc.

• 8
• 5
• 6
• 7

Answer explanation

M10,M15,M20,M25,M30,M35,M40-7 grades

What is the yield strength of HYSD bars ?

• 250 N/mm2
• 140 N/mm2
• 415 N/mm2
• 230 N/mm2

Answer explanation

HYSD - Fe415 (≈ 415 N/mm²)

Plain mild steel have a yield point of ....... N/mm2

• 140
• 250
• 415
• 515

Answer explanation

Typical yield stress of plain mild steel ≈ 250 N/mm²; HYSD grades start at 415 N/mm².

Grades of concrete for RCC shall not be less than :

• M10
• M15
• M20
• M7.5

Answer explanation

For RCC, minimum grade is M20 as per IS 456.