Corrosion of Rebars can occur in non-carbonated concrete due to the presence of chlorides. This type of corrosion is called chloride corrosion.
The presence of chlorides is due either to being added to the concrete mixture or to its presence in aggregates or mixing water, or it may be due to its infiltration from an external source to the hard concrete.
They then dissolve in the water inside the cavities. When the salt dissolves in water, it is rapidly decomposed into electrically charged particles called ions: negative chloride ions neutralize the “susceptibility of iron oxide” layer of the rebar surface.
The high percentage of chloride at the time of concrete mixing may be combined with the materials derived from hydratation and may not be available for activation. On the other hand, chloride entered in the hardened concrete may be converted into released ions on a large scale and be available for activation.
The chloride ions in concrete are in two forms, free chloride ions, and compound chloride ions. Compound chloride ions combine with the materials obtained from hydration in cement paste, especially Tricalcium aluminate. The ions that cause damage and corrode the steel are free chloride ions.
The chlorides do not attack concrete except at very high concentrations. The formation of rust due to chloride attack can cause the concrete to break due to a significant increase in the volume of steel at the time of rust formation. Subsequently, there is a three to four times increase the original thickness of the steel.
To prevent the corrosion of the bars, NSG-Z90 as an effective product of NSG Co. can be applied to the concrete surface in the form of resin and compound in the grout. This product also seals the concrete surfaces as well. Another product is NSG-N50 which can be used as a concrete additive with the proportion %2 of the cement weight to the concrete to drastically reduce the concrete permeability and increase its resistance remarkably.
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