Ettringite-based binder from ladle slag: From hydration to its fiber-reinforced composites

Thesis event information

Date and time of the thesis defence

Place of the thesis defence

Linnanmaa, auditorium L6, remote connection: https://oulu.zoom.us/s/62737767318

Topic of the dissertation

Ettringite-based binder from ladle slag: From hydration to its fiber-reinforced composites

Doctoral candidate

Master of Science in Engineering Hoang Nguyen

Faculty and unit

University of Oulu Graduate School, Faculty of Technology, Fibre and Particle Engineering Research Unit

Subject of study

Process Engineering

Opponent

Docent Harald Justnes, SINTEF Building and Infrastructure (Norway)

Custos

Professor Mirja Illikainen, University of Oulu

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Two pathways for better utilization of ladle slag from steel industry

Ladle slag (LS) is a by-product of refining molten steel. Given that the production of one ton of crude steel produces 12–15 kg of LS, Europe produces approximately 2.6 million tons of this slag annually. In Finland, LS currently has limited use in low-value applications. It has shown high potential in producing cementitious binders due to its high calcium and aluminum content.

The goal of this thesis is to offer the best solution to utilize LS in the construction industry for both its environmental and economic benefits. To achieve this goal, the present research focuses on two pathways: (1) Developing a cementitious binder with minimal pre-treatment for raw materials and chemicals that meets the requirements to be used as a construction material, (2) Producing a high-performance fiber-reinforced cementitious composite from the LS-based binder with a good balance of high mechanical performance, small carbon footprint, embodied energy, and high durability.

This thesis is based on studies that have found that LS can hydrate with gypsum to form an ettringite-based binder for which the only treatment needed is milling the precursors. Citric acid works effectively in the binder as a set retarder to control setting time and workability. The binder can thus be used in various construction applications.

Polypropylene fiber can be used to produce the most balanced ettringite-based composite considering mechanical performance, CO2 emission, and embodied energy with great resistance under chemical and physical stress. The results of this thesis will enable better utilization of LS for high-value construction applications.
Last updated: 3.6.2020