This session, honoring Professor Carolyn Hansson and her over forty years of service to the profession, is focused on the future of the research, development and professional practice in the field of corrosion of steel in concrete structures. This session is intended to look into the future to provide a framework for new advancements in the field, given the problems that have not been fully solved by past research and challenges that have been introduced by the concrete industry’s need to reduce its carbon footprint.
Learning Objectives:
(1) Discuss perspectives on future cement based materials and durability;
(2) Identify electrochemical techniques and concepts for characterization, assessment, and forecasting of reinforcement corrosion;
(3) Examine steel-concrete interface and its impact on corrosion;
(4) Examine the processes associated with chloride-induced steel corrosion in concrete.
This session has been approved by AIA and ICC for 2 PDHs (0.2 CEUs). Please note: You must attend the live session for the entire duration to receive credit. On-demand sessions do not qualify for PDH/CEU credit.
Carolyn's Contribution to Electrochemical Chloride Extraction and Other Electrochemical Techniques
Presented By: David Whitmore
Affiliation: Vector Corrosion Technologies Ltd.
Description: Carolyn's role in modelling the electrochemical properties and verifying the performance of Electrochemical Chloride Extraction (ECE) was instrumental in the development of industry standards and performance criteria. This presentation will also provide an overview of the ECE technique, how it is implemented in the field.
The Effects of Cations on Chloride Ingress and Hydroxide Levels in Concrete
Presented By: Neal Berke
Affiliation: Tourney Consulting Group, LLC
Description: This presentation 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.
High-Throughput Analysis of the Kinetics of Chloride-Induced Passive Layer Breakdown in Different Carbon Steel Microstructures within Simulated Concrete Pore Solution
Presented By: Amir Poursaee
Affiliation: Clemson University
Description: Carbon steel bars are critical in steel-reinforced concrete structures, and their corrosion leads to significant deterioration. The formation of a passive layer on the steel surface plays a crucial role in delaying corrosion. Using a high throughput approach, this research explored the kinetics of the passive layer breakdown on different microstructures within carbon steel. Thermomechanical treated steel bars with three distinct microstructures, i.e., 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 72 hours of immersion, the solution was contaminated with 0.6M chloride ions. Scanning electrochemical microscopy was employed to study the kinetics of the passive layer breakdown and the effective rate constant of the species inside the solution on each microstructure. Results showed that the breakdown of the passive layer is a time-dependent process, and the microstructure influenced its kinetics.
How Concrete Corrosion Macrocells Affect Assessment and Forecasting
Presented By: Alberto Sagues
Affiliation: University of South Florida
Description: 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 crafting next generation models. This paper traces the evolution of understanding of these issues by the corrosion in concrete community, and anticipates challenges to be resolved next.
The Steel-Concrete Interface and Its Impact on Corrosion – An Updated Review and Research Perspectives
Presented By: Ueli Angst
Affiliation: ETH Zurich, IFB
Description: It is well known that the steel–concrete interface (SCI) influences corrosion of steel in concrete. Numerous factors related to the SCI, including steel surface characteristics, interfacial concrete properties (voids, cracks, etc.), and conditions related to the exposure (e.g. SCI moisture state) have been hypothesized to affect the mechanism of corrosion initiation and propagation. 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 novel experimental methodology. Finally, perspectives for future research are given.
50 Shades of Deicers and Anti-Icers
Presented By: Robert D Hooton
Affiliation: University of Toronto
Description: This presentation will focus on the use of deicers and anti-icers that are critical in reinforcement corrosion in concrete highway structures. There are several misconceptions and assumptions about deicers and anti-icers, and their variability makes it harder to understand their role in the process of reinforcement corrosion. This presentation will demonstrate these challenges and offer a better understanding on the subject.
Chloride Thresholds and Service Life Modeling of Structures Reinforced with Galvanized Steel
Presented By: Michael Brown
Affiliation: Wiss Janney Elstner Associates, Inc.
Description: This presentation will focus on the chloride thresholds and service life modeling of structures reinforced with galvanized steel. The conept of chloride thresholds is a controversial subject, especially when corrosion resistant reinforcements such as galvanized steel rebars are used, therefore, this presentation will provide a better understanding on the subject. The discussion will be expanded to service life modeling of structures reinforced with galvanized steel.
Perspectives on Future Cement Based Materials and Durability
Presented By: Karen Scrivener
Affiliation: Ecole Polytechnique Federale de Lausanne
Description: It is very important to reduce as much as possible the CO2 emissions associated with cementitious materials. One of the easiest ways to do this is to replace as much as possible of “clinker” with other cementitious materials (SCMs). This has important implication for durability. In general SCMs increase the resistance to chloride penetration, which is the main cause of corrosion. Interestingly our work indicates that this improvement seems to be directly related to the impact of the SCMs on the composition of the calcium silicate hydrate and the pore solution, with changes in the pore structure and binding being secondary effects. On the other hand low carbon concretes inevitably have less capacity to reabsorb CO2 during the recarbonation process. Which may result in faster carbonation, but it is now clear that carbonation, does not necessarily mean corrosion of steel reinforcement is inevitable. Furthermore much cement is used without reinforcement. In this presentation I will draw on some of our recent research results to give some perspectives on how future cement based materials should evolve and how we can ensure that these materials are fit for purpose over their service life.