Under normal conditions using ordinary Portland cement, the period of removal of the form work is:
Correct Answer: D. All options are correct
📚 Detailed Explanation: Verifying All Three Stripping Time Statements
Why D (All options correct) is correct: Each statement maps directly to a row in the IS 456:2000 formwork stripping table for Ordinary Portland Cement.
IS 456:2000 Reference Table
| S.No. | Type of Formwork | OPC (Minimum Period) | RHC (Minimum Period) |
|---|---|---|---|
| 1 | Vertical formwork to columns, walls, beams | 16–24 hours | 12 hours |
| 2 | Soffit formwork to slabs (props refixed immediately) | 3 days | 2 days |
| 3 | Soffit formwork to beams (props refixed immediately) | 7 days | 5 days |
| 4a | Props to slabs: spanning up to 4.5 m | 7 days | 5 days |
| 4b | Props to slabs: spanning over 4.5 m | 14 days | 10 days |
| 5a | Props to beams and arches: spanning up to 6 m | 14 days | 10 days |
| 5b | Props to beams and arches: spanning over 6 m | 21 days | 14 days |
Verification of Each Statement
| Statement | IS 456 Reference | Verdict |
|---|---|---|
| A. 7 days for beam soffits | Row 3: Soffit formwork to beams = 7 days (OPC) | Correct |
| B. 14 days for slabs spanning 4.6 m and more | Row 4b: Props to slabs spanning over 4.5 m = 14 days | Correct |
| C. 21 days for beams over 6 m spans | Row 5b: Props to beams spanning over 6 m = 21 days | Correct |
- Longer spans require longer curing before prop removal because the bending moment (and thus required concrete strength) is greater.
- All three values apply to OPC under normal conditions. Rapid Hardening Cement allows earlier striking.