The use of electrical resistivity as a NDT for the specification of concrete durability

Abstract

The calculation of the time to reinforcement corrosion and service life duration is a subject of increasing interest. In present communication is explained how to use the electrical resistivity to calculate both the initiation and propagation periods in the case of carbonation and chloride penetration, although only the case of chlorides is illustrated here. The main advantage is that resistivity is an inexpensive non destructive measurement that can be used for routine quality control. The resistivity is an indication of the porosity and pore connectivity. It increases with time as hydration proceeds which is an indication of aging or pore refinement. In addition to the measurement of the resistivity it is necessary to calculate a "reaction factor" for accounting of the binding with cement phases. Conceming the propagation period, the electrical resistivity is an indication of the moisture content of concrete and therefore, it has a relationship with the corrosion cement. A model is proposed in which the resistivity is introduced in the square root of time law