International Concrete Abstracts Portal

Professor Carolyn Hansson’s remarkable journey began in England, during the turbulence of the Second World War. Despite the hardships of wartime and the limitations imposed by rationing, Carolyn was raised in a nurturing environment by parents who instilled in her a deep respect for learning and perseverance. These values would guide her through an exceptional academic and professional life. As the sole woman at the Royal School of Mines, Carolyn studied metallurgy at Imperial College, where she later earned her PhD, focusing on superconductivity and crystal structures at liquid helium temperatures. Her postdoctoral path led her from industrial research at Martin Marietta Laboratories to academic positions at Columbia University and the State University of New York at Stony Brook, and later to Bell Laboratories in 1976. Her pivotal shift into corrosion science began in 1980 at the Danish Corrosion Centre, where she worked on a new type of cement and corrosion of steel in concrete. From Denmark to Canada, Professor Hansson continued her research at Queen’s University and later at the University of Waterloo, building an enduring legacy in the field of steel corrosion in concrete structures. Over the decades, Carolyn’s contributions to corrosion research have shaped and guided generations of engineers and scientists. Her pioneering studies—on electrical resistivity of concrete, quantifying reinforcement corrosion rates, and understanding the complex role of chlorides—remain foundational in the field. Her investigations into corrosion inhibitors, electrochemical chloride extraction, effects of concrete cracking on reinforcement corrosion, and corrosion-resistant steels continue to influence global practices in infrastructure resilience. This Special Publication celebrates more than 60 years of Professor Hansson’s contributions as a scientist, educator, and mentor. The papers collected here, presented at the 2025 Spring Convention in Toronto, reflect not only the lasting relevance of her work but also its future promise. Her vision stands as both a mirror to the past and a beacon for innovations yet to come in corrosion-resistant construction. O. Burkan Isgor David Tepke Ceki Halmen Neal Berke

Carbon steel bars are critical in steel-reinforced concrete structures and their corrosion leads to significant deterioration. Using a high-throughput approach, this study explored the kinetics of passive layer breakdown on different microstructures within a carbon steel reinforcing bar. Thermomechanically treated steel bars with three distinct microstructures (martensite in the outer layer, bainite in the middle, and pearlite in the center) were vertically cut and immersed in the simulated concrete pore solution. After 24 hours of immersion, the solution was contaminated with 0.8M chloride ions. Scanning Electrochemical Microscopy (SECM) was employed to study the kinetics of the passive layer breakdown on each microstructure. The results showed that the breakdown of the passive layer was a time-dependent process and that the microstructure influenced its kinetics.

Corrosion of steel in concrete involves interactions between net anodic and cathodic regions that may extend into the cm, m or multi-m range. Such broad macrocells conveniently help corrosion detection methods based on half-cell potential surveys. However, the macrocells can also complicate the interpretation of polarization measurements of corrosion rates, leading to over or under estimates depending on the chosen placement of the sensor electrodes. Corrosion macrocells can also make interdependent the corrosion initiation and propagation stages of contiguous parts of a structure, by mutually affecting chloride threshold values and corrosion rates. Damage evolution forecasts change considerably when interdependence is taken into consideration, an issue of importance in creating next generation models. This paper addresses understanding by the corrosion in concrete community in a selection of these issues, and anticipates challenges to be resolved next.

This paper demonstrates how a model that includes the chemical reactions in concrete, as well as the tortuosity of the concrete, can be used to predict the effects of cations on the ingress of chloride and changes in the hydroxide levels. Scenarios using low and high C3A cements exposed to NaCl, KCl, CaCl2, and MgCl2 are modeled. The predictions are compared to test data presented several years ago by Professor Hansson. The modeling provides a rapid means that can be used to assess both the salt and cement type on the corrosion susceptibility of embedded steel reinforcement in concrete.

It is well known that the steel–concrete interface (SCI) influences corrosion of steel in concrete. Numerous factors related to the SCI have been hypothesized to affect the mechanism of corrosion initiation and propagation, including steel surface characteristics, interfacial concrete properties (voids, cracks, etc.), and conditions related to the exposure (e.g., SCI moisture state). This contribution offers an overview of current knowledge on these aspects. Additionally, recent advances toward a fundamental understanding of corrosion-related processes occurring at the SCI are highlighted, including a novel experimental methodology for studying the steel surface behavior, imaging of the SCI moisture state, and the impact of macroscopic voids. Finally, perspectives for future research are given.