For assessing the possible rate of corrosion in reinforcing bars. The time at which corrosion of steel may commence and the rate at which it may proceed is dependent upon properties of the cement paste and the permeability of the concrete. Since the electrical conductivity of concrete is an electrolytic process, which takes place by ionic movement in the aqueous pore solution of the cement matrix, it follows that a highly permeable concrete will have a high conductivity and low electrical resistance.
Thus knowledge of the electrical resistance of a concrete can provide a measure of the possible rate of corrosion of steel embedded in it.