Concrete degradation

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Concrete degradation may have many different causes. Concrete is mostly damaged by the corrosion of reinforcement bars due to the carbonatation of hardened cement paste or chloride attack under wet conditions. Chemical damage is caused by the formation of expansive products produced by chemical reactions (from carbonatation, chlorides, sulfates and distillate water), by aggressive chemical species present in groundwater and seawater (chlorides, sulfates, magnesium ions), or by microorganisms (bacteria, fungi...) Other damaging processes can also involve calcium leaching by water infiltration, physical phenomena initiating cracks formation and propagation, fire or radiant heat, aggregate expansion, sea water effects, leaching, and erosion by fast-flowing water.^[1]

The most destructive agent of concrete structures and components is probably water. Indeed, water often directly participates to chemical reactions as a reagent and is always necessary as a solvent, or a reacting medium, making transport of solutes and reactions possible. Without water, many harmful reactions cannot progress, or are so slow that their harmful consequences become negligible during the planned service life of the construction. Dry concrete has a much longer lifetime than water saturated concrete in contact with circulating water. So, when possible, concrete must first be protected from water infiltrations.