Reliability of Galvanostatic Pulse Technique in assessing the corrosion rate of rebar in concrete structures: Laboratory vs field studies

Abstract

Corrosion of rebar in concrete structures is one among the various causes impairing its long-term durability. Precise assessment of corrosion rate (CR) is of prime importance to evaluate the structural safety as well as for estimation of service life of concrete structures. Among the electrochemical techniques, Galvanostatic Pulse Technique (GPT) is very promising for field mapping due to its rapidity. The reliability of GPT in determining the CR under passive and active state of rebar has been carried out using small size laboratory specimens and large scale aged concrete structures. The CR determined by the GPT is compared with the CR obtained by Electrochemical Impedance Spectroscopy Technique (EIST) and weight-loss method. The study reveals that an anodic pulse of 100 µA with a pulse duration of 10 seconds is able to determine the CR from 1-663 µm/y (from negligible to higher corrosion activity) on the rebar network more precisely even up to 65 mm of cover concrete. For instance the rebar corroding at higher rate, the CR predicted by GPT is very close to the CR by weight-loss method whereas it is 20 times less by EIST. In the case of passive state of rebar, the CR predicted by EIST is very close to weight-loss method whereas GPT predicts 10 times higher. In aged structures, the change in microstructure of concrete and loss of moisture from the concrete make the potential of rebar and resistivity of concrete more unpredictable and mislead the status of rebar embedded inside the concrete.

Manufacturing Errors of Concrete Cover as a Reason of Reinforcement Corrosion in a Precast Element—Case Study

“…The usually used potential mapping technique, measuring half-cell potential on concrete surface sometimes led to misinterpretation especially in structures placed in wet and anaerobic environment [25][26][27]. For this reason the galvanostatic pulse technique has been introduced [25][26][27][28]. Both electrochemical methods assume that corrosion of reinforcement in concrete is an electrochemical process in which a steel reinforcing bar is an electrode and the alkaline liquid filling the pores of the concrete is an electrolyte.…”

Non-Destructive Evaluation for Corrosion Monitoring in Concrete: A Review and Capability of Acoustic Emission Technique

“…The GPM results are much closer to the corrosion rate produced by the gravimetric method than those produced by polarization resistance, electrochemical impedance spectroscopy (EIS), the Tafel extrapolation method (TEM), and the harmonic analysis method (HAM) [ 13 , 14 , 19 , 41 , 42 ]. Uncertainty about the polarized area of steel reinforcement is one of the major sources of error when measuring the corrosion rate of steel reinforcement in RC structures affected by the electrical signal from the counter electrode and the non-uniform current distribution of the steel reinforcement [ 43 ].…”

“…Electrochemical methods are by far the most suitable for corrosion monitoring in RC structures. Electrochemical methods, in general, can provide fast and reliable information on the probability of corrosion, the corrosion rate of steel reinforcement, and the resistivity of the concrete structure [ 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ]. Electrochemical methods are related to the interrelation of the electrical and the chemical effects.…”

Methodology for Assessing the Probability of Corrosion in Concrete Structures on the Basis of Half‐Cell Potential and Concrete Resistivity Measurements

“…In [28] it was shown that the combination of the method described in [29] and the conventional method of measuring concrete resistivity could be a reliable tool for directly determining the corrosion rate of the reinforcement in concrete. In paper [30] for this purpose Vedalakshmi et al used the galvanostatic pulse technique with electrochemical impedance spectroscopy and the weight-loss method. Rhazi [31] measured concrete resistivity ρ in the same locations where half-cell potentials were measured, but it should be noted that the measurements were carried out on a concrete bridge deck covered with asphalt.…”