Civil war Day 5(Sep 19)-LSGD

If aggregate cement ratio is low it is a

• leaner aggregate
• fatty concrete
• green concrete
• none of these

Answer explanation

If aggregate–cement ratio is low …” → that means more cement is present in the mix → it becomes fatty concrete.

For given water content, workability decreases if the concrete aggregates contain an excess of

• elongated and flaky particles
• rounded particles
• particles with least surface area
• all of these

Answer explanation

Elongated and flaky particles increase surface area and interlocking, reducing workability.

Which statement is not correct.

• Well graded aggregates are more workable
• Round size aggregates are more workable
• For a given quantity of paste, bigger size aggregates are more workable
• The higher the aggregate cement ratio, higher is the workability

Answer explanation

Higher aggregate–cement ratio means less paste per aggregate, which reduces workability.

Strength of concrete below which not more than 5% of test result are expected to fail

• Tensile strength of concrete
• Characteristic compressive strength
• Flexural tensile strength of concrete
• Splitting tensile strength of concrete

Answer explanation

As per IS 456, characteristic compressive strength is the value below which 5% of results may fall.

The height / diameter ratio for cylinder in compression strength test is:

• 0.50
• 0.25
• 2.00
• 0.30

Answer explanation

Standard test cylinders have height twice the diameter (h/d = 2.0).

1:1:2 mix corresponds to which grade of concrete

• M20
• M25
• M15
• M30

Answer explanation

Nominal concrete mix 1:1:2 corresponds to M25 grade.

Which of the following is a key ingredient in the preparation of high performance concrete?

• Silica fume
• Volcanic ash
• Blast furnace slag
• Pumice

Answer explanation

Silica fume improves strength and durability of high performance concrete.

In ferrocement construction, what is the reinforcement ?

• 8 mm rod
• 6 mm rod
• 4 mm rod
• Wire-mesh

Answer explanation

Ferrocement uses wire mesh as reinforcement in thin sections.

The concrete slump recommended for beams and slabs is

• 25–75 mm
• 130–150 mm
• 30–125 mm
• 25–50 mm

Answer explanation

According to IS 456 and IS 10262:

• Slump range for beams and slabs = 30 mm to 125 mm

Cube strength is found to be approximately ........... times the cylinder strength.

• 0.80
• 0.85
• 0.67
• 1.25

Answer explanation

Cube strength is about 1.25 times the cylinder strength.