Pavement Design MCQ with answer and solution

Concept

In concrete pavements laid in winter, the slab will expand later in summer, so expansion joints are kept close: about 50-60 m for a smooth interface.

Step-by-step solution

1. Expansion joints allow the concrete slab to expand in hot weather. 2. A slab cast in winter (low temperature) will expand a lot in summer, so joints must be closer. 3. A smooth interface (low friction with the base) gives less restraint, so the slab moves more freely and needs closer joints. 4. IRC guidance gives about 50 m (thinner slabs) to 60 m (thicker slabs) for a smooth interface in winter. 5. So the answer is 50 to 60 m, option (A).

Explanation

Concrete laid in winter expands more when summer comes, so expansion joints are placed closer together. For a smooth interface, IRC recommends a maximum spacing of about 50-60 m. Larger spacings apply to summer casting or to a rough interface.

Why the other options are wrong

(B), (C) and (D) are larger spacings. These apply to summer-laid slabs or a rough interface, not to a smooth interface in winter.

Shortcut

Winter + smooth interface = smallest spacing, about 50-60 m.

Common mistake

Choosing the summer value (about 140 m) instead of the winter value.