The permissible value of chloride ion penetrability in concrete in coulombs is typically 0.6 coulombs. This value is determined by testing the concrete samples for chloride ion concentration over some time. Chloride ions, when present in large concentrations, can cause corrosion of steel reinforcement in concrete structures. Therefore, it is essential to ensure that the chloride ion penetrability in concrete is kept within the prescribed limits (Burda & Brown, 2008). The amount of chloride ion penetration in concrete depends on a variety of factors, including the type and age of the concrete, the exposure to deicing salts and other sources of chloride ions, the porosity of the concrete, and the permeability of the concrete (Mehta & Monteiro, 2006). The concrete's permeability can be determined using a resistivity meter, which measures the material's electrical resistance. The resistivity of the concrete is then converted to coulombs, which is the unit used to measure the chloride ion penetrability in concrete (Mehta & Monteiro, 2006). To ensure that a concrete structure does not experience corrosion due to chloride ion penetrability, a maximum chloride ion penetrability of 0.6 coulombs is typically recommended (Mehta & Monteiro, 2006). Suppose the chloride ion penetrability is higher than 0.6 coulombs. In that case, the concrete structure should be evaluated for potentially increasing its durability of the structure, such as by adding a waterproofing agent or applying a sealant to the surface (Mehta & Monteiro, 2006). In summary, the permissible value of chloride ion penetrability in concrete in coulombs is typically 0.6 coulombs. This value is determined by testing the concrete samples for chloride ion concentration over some time. If the chloride ion penetrability is higher than 0.6 coulombs, the concrete structure should be evaluated for potentially increasing durability of the structure.

References:

Burda, M., & Brown, M. (2008). Chloride penetration in concrete. Advances in Cement Research, 20(3), 131–136.

Mehta, P. K., & Monteiro, P. J. M. (2006). Concrete: Microstructure, properties, and materials. New York, NY: McGraw-Hill.