Question

While testing the compressive strength of cement concrete, the correct standard conditions (viz temperature, age, humidity and size of the specimen) to be maintained as per IS are
1. 27 ± 3°C, 28 days, 90% and 15 cm cube
2. 26 ± 2°C, 28 days, 80% and 15 cm cube
3. 25 ± 1°C, 14 days, 75% and 10 cm cube
4. 27 ± 3°C, 7 days, 70% and 10 cm cube

Answer 1

Correct Answer - Option 1 : 27 ± 3°C, 28 days, 90% and 15 cm cube

Concept-

Temperature-

All materials shall be brought to room temperature, preferably 27 ' ± 3˚C before commencing the tests.

During the test of concrete the temperature should be 27 ' ± 3˚C.

Size of specimen-

Test specimens cubical in shape shall be 15 X 15 X 15 cm. If the largest nominal size of the aggregate does not exceed 2 cm, 10 cm cubes may be used as an alternative. Cylindrical test specimens shall have a length equal to twice the diameter. They shall be 15 cm in diameter and 30 cm long.

Humidity and age-

The test specimen- shall be stored in a place, free from vibration, in moist air of at least 90 percent relative humidity and at a temperature of 27° ± 2°c for 24 hours.

To determine the compressive strength of concrete it should be cured for 28 days.

So while testing the compressive strength of cement concrete, the correct standard conditions (viz temperature, age, humidity and size of the specimen) to be maintained as per IS are  27 ± 3°C, 28 days, 90% and 15 cm cube .