A NEW TECHNIQUE FOR THE MEASUREMENT OF THE ELECTRICAL-RESISTIVITY OF CONCRETE

The measurement of electrical resistivity is quite important in the st udy of concrete properties, since it provides information on permeabil ity and hence the durability and strength. In addition, the rate of tr ansport of aggressive ions like chlorides and sulphates, which lead to corrosion of the reinforcing steel, is controlled by permeability. In this Paper a simple and elegant technique for measuring the electrica l resistivity of concrete is described. The method consists in the app lication of a current pulse to the steel-concrete system immersed in a n electrolyte, and measuring the amplitude of the potential step, eith er using an oscilloscope or a digital voltmeter through an interface c ircuit. Using this technique the variation of the resistivity of concr ete has been measured as a function of the curing time. The resulting curve has been found to follow a hyperbolic expression; this is correl ated with the curve of the variation of compressive strength with time .