The GATE Grind

GATE 2026 CE (CE2) – Question 40

Highway Pavements · Design of flexible and rigid pavements · 2 marks · Multiple choice

Consider the following statements with respect to rigid pavements:

Statement-1: Bottom-up cracking (BUC) in rigid pavements is caused at the edge of the slab due to combined effect of single or tandem rear axle load and positive temperature differential.

Statement-2: Top-down fatigue cracking (TDC) in rigid pavements is caused due to repeated cycles of axle loads and negative temperature differential.

The CORRECT option is:

  1. Both statements are TRUE.
  2. Statement-1 is TRUE, but Statement-2 is FALSE.
  3. Statement-1 is FALSE, but Statement-2 is TRUE.
  4. Both statements are FALSE.

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Correct answer: (A) Both statements are TRUE.

Explanation

By day the top of the slab is warmer than the bottom, the slab curls down at the edges and the bottom of the slab goes into tension. A heavy axle at the edge adds to that tension, which causes bottom-up cracking. At night the top is cooler, the slab curls up and the top goes into tension. Repeated axle loads then cause fatigue cracks that start at the top. Both statements are true.