Periodic Reporting for period 1 - PERFoRM (Passive layER FailuRe Mechanisms for Steel Embedded in Alkali-Activated Slag Materials)
Reporting period: 2019-06-03 to 2021-06-02
The key objectives of PERFoRM are:
1. Developing novel durability wireless embedded (D-WirE) sensors for in-situ monitoring of concretes
2. Ground-breaking monitoring of chemical and physical changes induced by carbonation/chloride penetration in NnSAS
3. Advanced characterisation of passive layer growth, breakdown, and failure rates of steel rebars embedded in NnSAS
4. Creation of service-life models by incorporation of in-situ carbonation and chloride penetration regression models
> Electrochemical characterization of time-dependent stability of passive films in alkaline simulated concrete pore solutions.
> Analysis of novel structural health monitoring and fiber-optic with Bragg grating sensor networks for physical and chemical data acquisition
> Data evaluation, analysis, and reporting of long-term electrochemical corrosion in reinforced partially-carbonated slag-metakaolin concrete materials specimens.
> Thermodynamic and electrolyte simulations of pore solutions of alkali and near-neutral salt activated slag materials to elucidate the passive layer formation, establishment, and maturity mechanisms underpinning their physical and electrochemical characteristics.
> Support the establishment and operation of UKCRIC National Centre for Infrastructure Materials micro-scale computerized tomography facility.
> Development of open-source mico-computerized tomography datasets of near-neutral salt-activated slag materials.
> Investigation on the pore structure networks (i.e. tortuosity, Cl diffusion) of sodium carbonate and sodium sulfate-activated slag materials.
> Written report on the use of wireless sensor technology and processing challenges for the future application of embedded sensors in cementitious materials.
> Contribution to the European Federation of Corrosion and RILEM TC CAM on chloride diffusion in alkali-activated materials.
> Organization of research colloquium co-sponsored by the University of Leeds Institute for Fluid Dynamics, Institute of Functional Surfaces, and the UK Collaboratorium for Research in Infrastructure and Cities.
Summary of main results and dissemination achieved:
> New understanding of the effect of the ionic conductivity of highly reductive pore solutions of slag-based AACs with novel relationships to steel metallurgical variables affecting the establishment, stability, and maturity of passive layers.
> The first reported long-term studies (335 days) on the CO2-induced corrosion performance of reinforced alkali-activated slag/metakaolin blended concretes.
> Successful production of long-timescale aged near-neutral salt activated slag materials (540 days) critical to inform service life models and performance-based materials designs.
> Development of a detailed set of research and operation procedures for the non-destructive research of novel cementitious materials utilizing micro-computerized tomography equipment.
> Dissemination of research in Science (Impact Factor = 41.845) as a perspective article on the role of sensors in the future of smart cities and cementitious materials.
> Development of micro-computerized tomographies of near-neutral salt-activated slag materials to investigate the mass transport and pore structure network of burgeoning low-CO2 cementitious materials.
Overall, the databases and simulation tools developed in the project will provide societal impact by providing a pathway for the decarbonization of urban infrastructure with improved durability against corrosion damage. The results from the PERFoRM project achieve this by elucidating for the first time the relationship between the pore solution chemistry and the formation, establishment, and maturity processes of the passive layer in low-carbon cementitious materials. In-depth data analysis results from the project also benefit infrastructure practitioners as well as durability engineers with updated information (e.g. Tafel constants) to better predict the corrosion rates of embedded reinforcement in low-carbon cementitious materials (i.e. alkali-activated slag materials). Consequently, a complete understanding of passive layer formation mechanisms paired with improved information to predict corrosion rates in low-carbon cementitious materials is important to improve the durability of these materials and, hence, enable their in-service application. Thus, by doing so, the decarbonization of urban architecture can be achieved with improved resilience against corrosion-induced damage.