This special issue in memoriam of esteemed Prof. Jose Antonio Gonzalez gathers contributions presented during the Research in Progress symposium organized by AMPP in 2022. The legacy and seminal work of Jose Antonio, particularly regarding the development and application of electrochemical techniques for studying corrosion in reinforced concrete structures, has impacted generations of science, engineering, and research and stands as a major contribution to the field.
The collection of articles will be featured in two special sections, covering the broad aspects related to the corrosion of steel in concrete. This first section discussing infrastructure, construction, building, and architecture, including the application of reinforced concrete utilization in offshore structures. Different aspects of corrosion of steel in concrete have been covered, including localized corrosion, uniform corrosion, chloride-induced corrosion, carbonation effects, new cementitious materials, geopolymer concrete, cracking, fatigue, corrosion inhibitors, electrochemical chloride removal, realkalinization, corrosion monitoring techniques, as well as modeling and simulation. Communications including original experimental research, modeling and simulation, technical notes, and even critical reviews are presented herein. New transformational concepts that will be crucial to the next century of buildings and infrastructure are also presented.
Nowadays, integrity of construction and infrastructure is of paramount importance to realize safe, durable, and long-lasting reinforced concrete structures (RCS). Resiliency of RCS can be impacted by the corrosion of reinforcing steel, with steel depassivation leading to concrete cover delamination and spalling. In this regard, sustainability and environmental aspects are considered as a challenge for the development of future civil engineering structures, where smart cities align with societal priorities. The application of novel technologies and materials will contribute to reducing the impact of infrastructure corrosion and failures in service.
The work by Ormellese, et al.,1 evaluates the application of a nitrate-based compound as corrosion inhibitor as an alternative to widely adopted nitrite-based inhibitors that are used in reinforced concrete structures. This work studies the efficiency and carbonation coefficient of a nitrate-based corrosion inhibitor on long-term exposure carbonated-induced corrosion in concrete. Results show that the addition of Ca(NO3)2 contributes to suppressing the carbonation penetration rate—by reducing the carbonation coefficient about 30% with respect to control samples.
The electrochemical and structural behavior of chloride contaminated reinforced concrete beams subjected to flexural loads and exposed to wet and dry cycles is presented by Moreno-Herrera, et al.2 Their findings conclude that the electrochemical corrosion behavior was consistent and independent of the applied tensile stresses (with respect to the yield strength, fy) considered in this study (0.4 fy and 0.8 fy). From a structural standpoint, the strength, stiffness, and ductility of the reinforced concrete beams were not influenced by the conditions of the corrosion exposure.
A comprehensive review paper by Melchers3 presents the mechanisms governing reinforcement corrosion in concretes in marine environments—and how they influence the manner of local failure of the concrete. The initiation of steel reinforcement corrosion in porous media can occur through two independent mechanisms including pitting at and near wet concrete air-voids when the chloride concentration is sufficient to neutralize the effect of elevated concrete pH, and additionally the slow dissolution of concrete alkalis (mainly Ca(OH)2) which lower pH and enable uniform corrosion to be thermodynamically feasible on the reinforcing bars.
A proof-of-concept electrochemical application based on the Wenner four-probe technique was developed by Díaz, et al.,4 where a non-contact procedure offers quantitative information on the concrete resistivity and reinforcement corrosion rate. The measured apparent polarization resistance enables determination of the true polarization resistance in a contactless mode, thus offering a versatile technique for reinforced concrete inspection and evaluation.
In a study by Dacio and colleagues,5 a new organic aromatic compound was studied as potential green corrosion inhibitor for reinforcing steel bars. It was determined that an optimal concentration of 3 mM provided an inhibition efficiency higher than 85%. The interfacial and adsorption properties were evaluated by electrochemical impedance spectroscopy, where organic molecule adsorption is suggested to form a protective film that decreases the area of rebar exposed to solution and increases the thickness of the film formed, thus providing protection against corrosion.
A study by Melchers and Richardson6 presents atmospheric corrosion studies of reinforced concrete under long-term atmospheric exposure. Their findings on carbonation and alkali loss explored well-compacted reinforced concrete columns, from the exterior and the interior of a 60-year-old in-land building. It was determined that theoretical thermodynamic conditions dictate that corrosion initiation of reinforcement can result only from the long-term dissolution and loss by leaching of calcium hydroxide from the concrete matrix. In summary, for high-quality well-made, uncracked reinforced concrete structures, the depth at which corrosion is feasible is less than 15 mm in 60 years and thus much less than the usual concrete cover.
The stress corrosion cracking (SCC) of type 2001 lean duplex stainless steel reinforcement in chloride contaminated concrete pore solution was presented in the work of Martin, et al.7 Electrochemical analysis and mechanical testing were utilized to evaluate passivity breakdown. It was found that ferrite phase served as a nucleation site for pits. Intergranular SCC was the prevailing corrosion process, which developed through the ferrite/austenite interface following anodic dissolution given the more active nature of the ferrite phase. Additionally, when high stress concentration was reached, a transgranular stress corrosion crack propagated through austenite phase, following the slip-step dissolution mechanism.
We hope the first part of this collection on corrosion of steel in concrete provides a comprehensive overview of contemporary research in progress, and that you enjoy it as much as we did. This collection carries on Jose Antonio’s memory by advancing the research on corrosion in reinforced concrete structures. We would like to take this opportunity to thank all authors for their valuable contribution to this special issue. Finally, we look forward to releasing the second section later this year.