Calculation of initiation and propagation periods of service life of reinforcements by using the electrical resistivity

Abstract

Reinforcement corrosion is attracting research interest in many areas due to the economic consequences of the damage generated by the process. Several proposals can be found on prediction of the time to reinforcement corrosion and service life duration. In the present communication a proposal is made on using the electrical resistivity to calculate both the initiation and propagation periods. For the time period to corrosion onset, the electrical resistivity serves to model the porosity and its connectivity and therefore can be used to calculate transport processes. Due to the reaction of chlorides and carbon dioxide with cement phases, the resistivity has to be factored by a “reaction factor”, r, to account for this. Concerning the propagation period, the electrical resistivity is an indication of the moisture content of concrete and therefore, it has a relationship with the corrosion current. The service life can be expressed with the following equation: $t_{l}=t_{i}+t_{p}=x^{2}rho_{es}{\frac {r_{CICO_{2}}}{k_{CI,CO_{2}}}}+{\frac {P_{x}.rho_{ef}}{k_{corr}}}$. Based on this, minimum resistivity values can be established according to cover thickness and as a function of exposure classes.