Important points to Ordinary Portland Cement(OPC)
The content provided in this article mainly asked in various examinations.
- We all know cement is made up of various constituents. But the main constituent responsible for initial setting of cement is tricalcium aluminate.
- As per IS specification, initial setting time should not be less than 30 minutes and final setting time is 10 hours.
- The strength of cement decreases on storing.
- For the testing of the compressive strength of cement, 50 mm size cubes were made up in 1:3 proportions.
- Normal consistency is about 30%.
- Early strength is due to finer grinding.
- For fineness test, Blaine method is used.
- Le-chatlier and Autoclave methods were used for soundness test.
- Three grades of OPC cement are 33, 43 and 53 as per IS.
- Maximum quantity of water needed per 50 kg of cement for M15 grade of concrete is 32 litres.
- According to Whitney’s, ultimate strain of strain of concrete is assumed to be 0.3%.
- Shrinkage of concrete depends upon humidity of atmosphere and passage of time.
- The heat of hydration of cement can be reduced by reducing the proportions of C3A (tricalcium aluminate) and C3S ( tricalcium silicate).
- Minimum water cement ratio required for full hydration of cement is 0.36
- The value of Vee-Bee time for low workability as per Indian Standards is prescribed as 5-10 seconds.
- As compared to moist-cured concrete, the permeability of steam-cured concrete is more.
- According to IS: 456-1978, the flexural strength of concrete is directly proportional to square root of compressive strength.
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