Formwork MCQ with answer and solution

Concept

A construction joint is left where concreting stops and is continued later.

Step-by-step solution

1. Concreting often cannot be done in one go. 2. Where work stops at the end of a day or pour, a joint is formed. 3. This joint between old and new concrete is called a construction joint. 4. Isolation, expansion and contraction joints are designed for movement, not for pouring breaks. 5. Answer: (A) Construction joint.

Explanation

A construction joint is made where one concreting operation ends and the next one starts later. It is planned at places of low shear, and the old surface is roughened and cleaned before new concrete is placed. Other joints are given to allow movement of concrete.

Why the other options are wrong

B: An isolation joint separates a slab from columns, walls or footings so they can move freely. C: An expansion joint allows concrete to expand due to temperature rise. D: A contraction joint controls cracking from shrinkage and temperature drop.

Shortcut

Stop pouring and restart later, so it is a construction joint.

Common mistake

Confusing a construction joint with a contraction joint because the names sound similar.