Marine Structures
When salt water combined with oxygen comes into contact with steel, the steel rusts. When steel rusts it expands. When the steel in question is the reinforcement for a concrete structure, the expanding steel causes the concrete surrounding it to spall.
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This is a simple explanation for a common occurance on concrete marine structures, or any place else exposed to salt and water. The unique bond capabilities of shotcrete have been utilized for decades when designers require the repair of concrete structure due to chlorine ion (salt) penetration.
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