As per IS code, the initial setting time of OPC should not be less than ___________and final setting time should not exceed________.
- A30, 300
- B30, 600Correct
- C60, 300
- D60, 600
Solution
Concept
Setting time limits for Ordinary Portland Cement ensure adequate workability time during handling and timely hardening for construction progress.
Step-by-step solution
1. Recall the IS code specifications for Ordinary Portland Cement (OPC). 2. Initial setting time minimum limit = 30 minutes. 3. Final setting time maximum limit = 600 minutes (10 hours). 4. Match these values with the given options to find option (B).
Explanation
As per IS 269 / IS 456, the initial setting time of Ordinary Portland Cement (OPC) should not be less than 30 minutes to allow proper mixing, transporting, and placing. The final setting time should not exceed 600 minutes (10 hours) to ensure that the concrete hardens within a reasonable time.
Why the other options are wrong
A: Final setting time 300 minutes is incorrect (it is 600 minutes). C: Initial setting time 60 minutes is incorrect (it is 30 minutes). D: Initial setting time 60 minutes is incorrect.
Shortcut
Remember 30 minutes for start (initial) and 10 hours (600 minutes) for finish (final).
Common mistake
Confusing minutes and hours, or mixing up initial and final setting time limits with other types of cements like rapid hardening cement.
Correct answer: B) 30, 600