Techniques of corrosion monitoring of steel rebar in reinforced concrete structures: A review

Abstract

Reinforcement corrosion is a major culprit that undermines the service life of reinforced concrete (RC) structures. It costs billions of dollars each year in the US alone and negatively impacts safety, reliability, resilience, and environmental performance of RC infrastructure. Corrosion monitoring of steel rebar is critical to provide early warning of deficiency, enable timely and effective maintenance strategies, and prevent catastrophes associated with premature failure of RC structures. To improve corrosion monitoring in the engineering practice, this work comprehensively reviews the state of the art of five major types of techniques, that is, electrochemical sensors, optical fiber sensors, sensors based on elastic wave methods, sensing based on electromagnetic methods, and untouched sensors. Each type of technique is systematically divided into sub-categories based on the sensing principle and key characteristics. For each sensor type, its maturity, application range, and the problems that hinder its application are discussed, aimed to provide guidance in selecting the appropriate sensors for specific engineering applications. This work concludes with an overview of opportunities and challenges, including the following six aspects for future research: spatial resolution, sensitivity, and measurement range; reliability and interpretation of the measurement; sensor selection based on three corrosion stages of steel rebar; long-term stability and service life; cost-efficiency of the sensing system; and monitoring of existing structure.

Inspecting the corrosion state of underground reinforced concrete structures

“…Those sensors typically consist of a plastic container filled with saturated copper sulfate solution, in which a blank pure copper rod is located. Plastic containers offer advantages over glass containers for field applications, such as robustness [19]. A porous plug, also known as the diaphragm, typically made of wood, ensures electrolytic contact to the concrete pore system or, in this application, over the conductive soil to the retaining wall made of RC.…”

“…To solve the challenge of the out-of-sight measurement, the design of conventional, commercially available CSE is adapted to determine the electrical resistance of the sensor with the stainless steel wire in order to detect malfunctions. High electrical resistances between the rebar and the RE were found to influence the HCP measurement [19], and continuous tracking of the electrical resistances overcame this limitation.…”

Low-Cost Technologies Used in Corrosion Monitoring

“…For corrosion monitoring systems, there are several literature reviews concerning different electrochemical methods used both for in situ and laboratory assessments [ 50 ], corrosion monitoring in atmospheric conditions [ 13 ], different techniques for monitoring the corrosion of steel rebar in reinforced concrete structures [ 51 ], using fiber optic sensors for the assessment of rebar corrosion in RC structures [ 52 ], and the advancement of a sensor capable of corrosion detection [ 53 ]. However, a systematic literature review on the use of LCSs and inexpensive technologies as low-cost solutions for corrosion monitoring applications is lacking.…”

A novel method for steel bar all-stage pitting corrosion monitoring using the feature-level fusion of ultrasonic direct waves and coda waves

“…The existing corrosion detection and monitoring methods of steel bars include visual methods, electrochemical testing methods, fiber-optic techniques and stress wave-based monitoring methods. 6 The corrosion products of reinforcements accumulate inside concrete and then lead to cracking of concrete when the force induced by corrosion products is higher than the tensile strength of concrete. The traditional manual vision-based inspection method detects reinforcement corrosion through the occurrences of concrete surface cracks, which is time-consuming, labor-intensive, and inaccurate.…”