Why do cracks develop in concrete?

Answer 1

Concrete is strong when compressed but relatively weak and brittle when stretched.

If the soil under the pavement is eroded, or expands during freezing, or is lifted enough by tree roots, the pavement will bend and crack on the convex side.

When concrete is poured, it warms as it hardens and then contracts slightly as it cools back down. If the poured block is long enough, then it will have enough contact with the Earth so the ends resist such movement, and the block will pull itself apart.

Highway pavement has steel mesh or even rebar (reinforcement bars) to resist the tensile (stretching) forces. It can only help to a certain extent. If such a pavement block is long enough, then normal environmental forces will exceed the reinforcement; heating and cooling the pavement, for example.

In addition, highway pavement is subject to high pressure from freight trucks and shock waves from high speed traffic. It is also poured in very long continuous sections. If there are not enough (closely spaced) contraction joints to attract inevitable cracking, then they will occur between contraction joints at random.

Answer:

Due to temperature stresses during hydration process, longitudinal and transverse cracks develop on concrete pavements.

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civil engineering - GITAM UNIVERSITY