How do map cracking and scaling differ in concrete?

• A. Map cracking is a single crack caused by shrinkage
• B. Map cracking is a network of interconnected cracks due to moisture movement; Scaling is flaking of the surface from freeze-thaw or abrasion
• C. Scaling occurs only in winter
• D. Map cracking and scaling are unrelated phenomena

Answer: (B)

Map cracking and scaling are two different ways concrete can deteriorate. Map cracking is a network of interconnected cracks that form a pattern across the surface. This happens as moisture moves in and out of the concrete, causing differential shrinkage and stresses that create many small cracks that connect like a map. Scaling, on the other hand, is the loss or flaking of the top surface cement paste. It shows up as a rough, powdery, or peeled layer on the surface and is typically driven by freeze-thaw action and abrasion (including de-icing salts), affecting only the surface layer.

So the correct idea is that map cracking is a network of interconnected cracks from moisture movement, while scaling is surface flaking from freeze-thaw or abrasion. The option describing a single crack is incorrect because map cracking is not just one crack, and the idea that scaling occurs only in winter is too restrictive since freeze-thaw damage can occur in cycles, not strictly limited to winter. They are related in that both are concrete distress, but they manifest and progress in different ways.