Concrete Damage and Problems
Concrete damage, defects and problems can be caused for many different reasons, or as a result of a combination of several root causes. These causes are normally referred to and classified as:
Damage that is caused by Mechanical, Physical or Chemical exposure, i.e.
- Mechanical impact, blast or abrasion damage.
- Physical attack from Freeze-Thaw action, or from Expansive Alkali Aggregate Reaction (AAR), - which is also known as Alkali Silica Reaction (ASR).
- Chemical Attack by aggressive soft water leaching, acidic liquid or gaseous attack, or other adverse chemical exposure.
Concrete Damage Due to Steel Reinforcement Corrosion
Concrete damage that is caused by the corrosion of the embedded steel reinforcement, i.e.
- Cracking and spalling concrete over the reinforcement due to expansive steel corrosion caused by carbonation of the concrete and loss of the protective alkalinity.
- Cracking and spalling over the reinforcement due to accelerated and expansive steel corrosion caused by chloride presence.
- Electro-potential differences with other metal elements or stray electric currents from elsewhere can also cause steel corrosion.
A summary and examples of Concrete Defects and Damage, plus Concrete Damage due to Reinforcement Corrosion is given in the following Two Tables:
|Concrete Defects and Damage|
|Example: Cracking caused by incorrect handling or fixing of precast panels.||Example: Chemical attack from aggressive gases (and subsequent reinforcement corrosion) on the top of chimneys or the soffits of a factory roof.||Example: Freeze/thaw effects with progressive scaling on the soffits of a parking structure.|
|Concrete Damage due to Reinforcement Corrosion|
|Carbonation||Stray / Electrical Current||Corrosive Contaminants e.g. Chlorides|
|Example: Reinforcement corrosion following reduction of the passivating concrete alkalinity, by natural atmospheric carbonation.||Example: Reinforcement corrosion evident as rust staining from cracks, after galvanised steel supports for parapet railings were fixed in direct contact with the embedded steel reinforcement.||Example: Steel corrosion accelerated by chloride ingress from de-icing salts used on a bridge and penetrating, particularly through the joints over the support piers.|
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