Rapid Chloride Penetration Test: Assessing Durability of Concrete

One of the major causes of deterioration in concrete structures, especially in the marine environment, coastal areas, and areas where de-icing salts are applied, is the corrosion of the reinforcing steel caused by chloride. The resistance of the chloride ingress in concrete depends on the ability of the concrete in question to endure, which has an immediate effect on the service life and durability of concrete. The Rapid Chloride Penetration Test provides a convenient laboratory method of determining this resistance by determining the electrical charge transferred through a piece of concrete under a certain voltage. 

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The concrete specimens are normally cast in the form of a cylinder and then sliced into discs of a diameter of approximately 50 mm. Before testing, the specimens are dipped into a vacuum to allow uniform test conditions in terms of moisture. Through the test, the flow of ions through the concrete at the voltage applied causes an electrical current to be produced; the current is continuously measured to determine the overall charge transfer.

When lower values of charge are observed, the chloride ion penetrability is reduced and, therefore, higher durability performance is achieved. The values of charge passed are divided into categories according to ASTM C1202, ranging from very low to high chloride penetrability. Concrete that includes some additional cementitious materials (fly ash, slag, silica fume) tends to have lower charge values because of lower pore connectivity and finer microstructure.

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