International Concrete Abstracts Portal

The suspended concrete ceiling beneath the Helmsley Building at 230 Park Avenue, Manhattan, New York, NY, USA, was successfully restored after cracking and staining were observed during a façade inspection. This article discusses the repair of the nearly 100-year-old concrete assembly in a highly constrained urban environment.

Chlorides in sufficient amounts contribute to the corrosion of reinforcing steel in concrete. However, there is no singular critical chloride threshold that covers every case. The industry’s understanding of the role of chlorides that may initiate corrosion is evolving. This article discusses various parameters affecting the critical chloride threshold and the sources of uncertainty associated with the concept.

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

To overcome the time- and resource-intensive electrochemical assessments used to evaluate the pitting corrosion resistance of stainless steel (SS) rebar alloys, a non-destructive assessment tool such as the Pitting Resistance Equivalent Number (PREN) index is important for decision-making involving building resilient engineering structures. By addressing the limitations of the existing PREN index, initially designed for SS alloys in hightemperature acidic or neutral environments, this study sought to develop a PREN index tailored for highly alkaline ambient-temperature concrete environments through a combination of electrochemical experimental analysis and machine learning modelling. This integrated approach and newly developed PREN index account for variations in SS alloying composition, concrete alkalinity, and environmental exposure conditions, addressing the growing demand for non-destructive, time- and cost-effective, and reliable alternatives for assessing SS rebar corrosion performance. Developed PREN will aid design of new and selection of existing SS alloys for reinforced concrete structures across diverse localities and applications. Two major formulas were reported, one for electrochemical parameters and the other for PREN related to these electrochemical parameters, each establishing their relationship with major SS alloying elements (i.e., Cr, Ni, Mo, Mn), concrete type (i.e. pH of testing solution), and concentration of deleterious species in exposure environment (i.e. chloride, sulphate). This study marks an initial step toward developing a non-destructive corrosion-performance assessment tool for civil engineering applications.

ACI Committee 365 published a new Design Specification in 2024. The Design Specification was developed to provide requirements to the Service Life Engineer, a specialty engineer focused on durability, for performing service life predictions of new structures. The Service Life Engineer is responsible for predicting the service life performance of concrete elements and developing requirements for the verification of the service life prediction during construction. The Service Life Report, developed during or prior to construction, and a Service Life Record Report, delivered at the completion of construction, are deliverables prepared by the Service Life Engineer at the completion of the project. The requirements of the Design Specification aim to provide consistency to the practice of service life prediction of new concrete structures. The technical requirements for performing service life predictions following the Design Specification are discussed in this paper.