Corrosion assessment in rebars of high-strength concrete using electromechanical impedance technique

Abstract

The corrosion of steel rebar in reinforced concrete structures is one of the main reasons for early deterioration and premature failure of concrete structures, leading to enormous restoration costs worldwide infrastructure restoration. In the past, many sensors and techniques have been developed to monitor corrosion in steel rebar. However, the Electromechanical Impedance (EMI) technique using the piezoelectric Lead Zirconate Titanate (PZT) patches has been immersed as a promising technique to detect damages at an incipient level. This paper presents the corrosion assessment in embedded rebar in high-strength concrete using surface-bonded PZT patches through the EMI technique. The High Yield Strength Deformed (HYSD) rebars of Fe415 grade embedded in high-strength M60 grade concrete cylindrical specimens were used for the experimental work. The artificial corrosion in the embedded rebar was simulated through the accelerated corrosion test for 180 days. The conductance signatures were acquired through a surface-bonded PZT patch on embedded rebar. First, qualitative and quantitative corrosion assessment was carried out based on the conductance signature and the Root Mean Square Deviation (RMSD). Second, the effectiveness of extracted equivalent parameters was demonstrated for capturing the degradation of stiffness and mass due to corrosion. Finally, the corrosion rate is evaluated through equivalent parameters, and a comparison was made with the actual mass loss. The experimental study demonstrated that the EMI technique could be used very effectively through the statical index RMSD and equivalent parameters to identify corrosion phases and resulting losses in stiffness and mass of the structure.