Formwork striking times with ordinary Portland cement (normal conditions): which of the following statements about typical removal periods is correct?

Introduction / Context:
Safe removal of formwork (shuttering) depends on cement type, curing temperature, and structural member type/span. Premature striking can cause deflection, cracking, or collapse, while unnecessarily long retention increases cost.

Given Data / Assumptions:

• Ordinary Portland cement, normal curing temperatures.
• Members: vertical sides, slabs, beam soffits with specified spans.
• Typical code-based guidance (conservative) for striking times.

Concept / Approach:
Vertical sides of walls/columns gain shape stability quickly and can be removed early (≈ 24–48 hours). Soffits carrying significant bending (long slabs/beam bottoms) require much longer to avoid overstress and excessive deflection: about 14 days for long slabs (≥ 4.6 m) and about 21 days for beams over ≈ 6 m span under normal conditions.

Step-by-Step Solution:
Match each member to typical striking guidance: columns/walls → 2 days; shorter slabs/beam soffits → 7 days typical; long slabs ≥ 4.6 m → 14 days; long beams ≥ 6 m → 21 days.Since each individual statement is correct, choose “All of the above”.

Verification / Alternative check:
Many specifications list similar minimums, with adjustments for rapid hardening cement, low temperatures, or imposed loads.

Why Other Options Are Wrong:
Choosing only one time ignores that all listed times correspond to accepted practice under the stated assumptions.

Common Pitfalls:
Forgetting that props (falsework) may remain longer than surface formwork; neglecting temperature effects on strength gain.

Final Answer:
All of the above