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Cracks due to reinforcement corrosion

Steel corrosion products (rust) usually occupy a much larger volume than the un-corroded steel and result in bursting stresses that can cause cracking and spalling of the concrete cover. The cracks that appear on the surface of the concrete will run parallel to the steel.

The reinforcing bars closest to the surface will generally be affected by corrosion first. Thus a typical occurrence of types of cracks due to corrosion will be over shear reinforcement on the sides and soffits of beams in exposed locations.

For further information see Concrete Society Technical Reports 44 and 54.

Crack due to reinforcement corrosion
Acknowledgement: The Concrete Society

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TR44 The relevance of cracking in concrete to corrosion of reinforcement - 2nd Edition

TR54 Diagnosis of deterioration in concrete structures- identification of defects, evaluation an