Chloride Resistance of Concrete

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Chloride Resistance of Concrete

Size: 2.6 MB | Format: PDF | Publisher: Cement Concrete & Aggregates Australia | Year: 2009 | pages: 37

Corrosion of steel reinforcement in concrete is the most common problem affecting the durability of reinforced concrete structures. Chloride-induced corrosion is one of the main mechanisms of deterioration affecting the long-term performance of such structures1. Concrete provides physical and chemical protection to the reinforcing steel from penetrating chlorides which may cause steel depassivation leading to increased risk of steel corrosion.
The chloride resistance depends on the permeability of the concrete and the thickness of cover to the reinforcement. The integrity of the concrete cover under service load, in terms of cracking and crack width, also influences the resistance to penetrating chlorides. Corrosion of steel reinforcement is an electrochemical process. Hence electrochemical properties of concrete, such as resistivity, are important inherent properties affecting the corrosion rate of reinforcing steel.
Metha2 reconfirmed from a review of case studies that it is the permeability of concrete, rather than its chemistry, which is the key to overall durability. The causes of high permeability are not limited to poor concrete proportion but poor concreting practice, such as incomplete mixing, inadequate consolidation and curing after placement, insufficient cover to reinforcing steel, and badly constructed joints. In service, concrete may exhibit various forms of cracking for reasons such as settlement, premature loading, overloads, and repeated impact. To obtain long-term durability of concrete marine structures, the control of concrete cracking in service through proper mix proportioning and concreting practice is of as much importance as the control of concrete permeability.
This report discusses the various factors affecting chloride resistance of concrete, mechanisms of chloride transport, related test methods and performance specifications. It also assesses additional measures to enhance the chloride resistance of concrete.

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