Civil war Day 23 LSGD-Concrete

Code specifying the details regarding coarse and fine aggregates.

• IS 383
• IS 800
• IS 456
• IS 10262

Answer explanation

IS 383 covers specifications for coarse and fine aggregates.

The process of removing holes and humps on the surface of concrete is termed as

• Levelling
• Floating
• Screeding
• Finishing

Answer explanation

Screeding strikes off excess concrete to level the surface.

Common sugar added to concrete :

• Increases the strength of concrete
• Retards the setting of concrete
• Accelerates the setting of concrete
• Gives colour to concrete

Answer explanation

Sugar acts as a retarder and delays setting.

The concrete slump recommend for beams and slabs is

• 25-50 mm
• 25-75 mm
• 50-100 mm
• 130-150 mm

Answer explanation

Beams and slabs require moderate slump (approx. 50–100 mm).

The increased cohesiveness of concrete, make it

• Less liable to segregation
• More liable to segregation
• More liable to bleeding
• More liable to surface scaling in frosty weather

Answer explanation

Higher cohesiveness reduces segregation.

The vibrators used for compacting large sections of mass concrete in structure is

• Screed vibrator
• Form vibrator
• Internal vibrator
• all of these

Answer explanation

Internal vibrators are suitable for deep/mass concrete.

Hydrophobic cement is obtained by grinding ordinary Portland cement clinker with

• Hydrochloric acid
• Oleic acid
• Glicerine
• Acetol

Answer explanation

Oleic acid coats cement particles making them moisture resistant.

The grade of concrete corresponding to nominal mix proportions of 1:3:6 is

• M 35
• M 25
• M 15
• M 10

Answer explanation

1:3:6 mix corresponds to grade M10.

The process of mixing, transporting, placing and compacting concrete using Ordinary Port land Cement should not take more than

• 30 minutes
• 40 minutes
• 60 minutes
• 90 minutes

Answer explanation

Concrete must be placed before initial setting begins (~30 min).

The top diameter, bottom diameter and the height of a slump mould are

• 10 cm, 20 cm, 30 cm
• 20 cm, 30 cm, 10 cm
• 10 cm, 30 cm, 20 cm
• 30 cm, 10 cm, 20 cm

Answer explanation

Standard slump cone dimensions are 10 cm top, 20 cm bottom, 30 cm height.