Use of brine in the preparation of alkali-activated materials
Thesis event information
Date and time of the thesis defence
Place of the thesis defence
L5, Linnanmaa campus
Topic of the dissertation
Use of brine in the preparation of alkali-activated materials
Doctoral candidate
Master of Science Sima Kamali
Faculty and unit
University of Oulu Graduate School, Faculty of Technology, Fibre and Particle Engineering research unit
Subject of study
Process engineering
Opponent
Professor Maria Bignozzi, University of Bologna
Custos
Associate Professor Tero Luukkonen, University of Oulu
Turning salty wastewater into sustainable building materials
Water-intensive industries produce large amounts of highly saline reject waters during membrane-based water treatment. These waters are difficult to manage because they contain concentrated salts and possible pollutants. This thesis investigates a new and more sustainable way to use such saline waters in the production of alkali-activated materials (AAMs), which are low-carbon alternatives to ordinary cement-based binders.
The study examined metakaolin, blast furnace slag, and their mixtures as raw materials. Different types of water were used to prepare alkaline activator solutions, including fresh water, simulated brines, and reverse osmosis reject waters from mining and pulp and paper industries. The results showed that blast furnace slag-based materials were especially effective in binding and immobilizing salts inside solid reaction products. This was mainly linked to the formation of stable mineral phases such as hydrotalcite and hydrocalumite.
Highly saline waters also improved the dissolution of slag and increased compressive strength compared with fresh water. In some cases, these waters allowed a major reduction, or even partial replacement, of conventional sodium hydroxide in the activator solution. Even with very low NaOH concentration, slag-based samples prepared with brine achieved good mechanical performance. This suggests that salts such as chloride and sulfate can support slag activation by interacting with calcium and magnesium and promoting dissolution.
Durability tests further confirmed the potential of brine-activated slag materials. The samples showed good dimensional stability, acceptable leaching behavior, improved strength after freeze-thaw exposure, and reasonable resistance to sulfuric acid attack. Overall, the thesis demonstrates that saline wastewaters and brines can be transformed from an environmental burden into useful components for producing durable alkali-activated construction materials. This approach offers a promising route for reducing freshwater use, lowering chemical consumption, managing saline wastes, and developing more sustainable cementitious binders for applications such as mine backfill and other construction uses.
The study examined metakaolin, blast furnace slag, and their mixtures as raw materials. Different types of water were used to prepare alkaline activator solutions, including fresh water, simulated brines, and reverse osmosis reject waters from mining and pulp and paper industries. The results showed that blast furnace slag-based materials were especially effective in binding and immobilizing salts inside solid reaction products. This was mainly linked to the formation of stable mineral phases such as hydrotalcite and hydrocalumite.
Highly saline waters also improved the dissolution of slag and increased compressive strength compared with fresh water. In some cases, these waters allowed a major reduction, or even partial replacement, of conventional sodium hydroxide in the activator solution. Even with very low NaOH concentration, slag-based samples prepared with brine achieved good mechanical performance. This suggests that salts such as chloride and sulfate can support slag activation by interacting with calcium and magnesium and promoting dissolution.
Durability tests further confirmed the potential of brine-activated slag materials. The samples showed good dimensional stability, acceptable leaching behavior, improved strength after freeze-thaw exposure, and reasonable resistance to sulfuric acid attack. Overall, the thesis demonstrates that saline wastewaters and brines can be transformed from an environmental burden into useful components for producing durable alkali-activated construction materials. This approach offers a promising route for reducing freshwater use, lowering chemical consumption, managing saline wastes, and developing more sustainable cementitious binders for applications such as mine backfill and other construction uses.
Created 27.4.2026 | Updated 27.4.2026