Formwork MCQ with answer and solution

Concept

IS 456:2000 gives the minimum stripping time for beam soffit formwork with props left under as 7 days (OPC, normal temperature).

Step-by-step solution

1. Recall the IS 456:2000 stripping times for OPC at normal conditions. 2. Vertical faces of columns, walls, beams: 16-24 h. 3. Slab soffits (props left under): 3 days. 4. Beam soffits (props left under): 7 days. 5. Props of slabs: 7 days (span ≤ 4.5 m), 14 days (span > 4.5 m). 6. Props of beams and arches: 14 days (span ≤ 6 m), 21 days (span > 6 m). 7. So the answer is 7 days.

Explanation

As per IS 456:2000, the soffit formwork of beams can be removed after 7 days if props are left under. The props stay longer, 14 or 21 days depending on span.

Why the other options are wrong

3 days: slab soffits (props left under). 14 days: props of beams up to 6 m span. 21 days: props of beams over 6 m span.

Shortcut

Soffit: slab 3, beam 7. Props: slab 7/14, beam 14/21.

Common mistake

Mixing up the soffit stripping time with the props removal time.