Effect of Reactive MgO Substitution on Strength Development and Microstructure Properties of Sodium Carbonate Activated Slag-Based Systems

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Özen Ö. C., Oktay D., Aktürk B.

15th International Congress on Advances in Civil Engineering, Gazimagusa, Cyprus (Kktc), 6 - 08 September 2023, pp.121-130

  • Publication Type: Conference Paper / Full Text
  • City: Gazimagusa
  • Country: Cyprus (Kktc)
  • Page Numbers: pp.121-130
  • Yıldız Technical University Affiliated: Yes


The high CO2 emission and energy consumption caused by the production of cement, increases the need for more sustainable options today. Accordingly, replacing cement with natural pozzolans or by-products is a solution that reduces energy consumption and CO2 emissions. Another alternative is alkali-activated materials (AAM), produced by calcium and/or silicon and aluminum-rich mineral additives instead of cement, and gaining strength after activation with alkaline activators. Sodium carbonate is one type of activator that can be obtained more easily compared to other alkaline activators has a high amount of reserves in Turkey. Drawbacks of sodium carbonate activation such as low early age strength and long setting times can be improved by using of various auxiliary materials such as slaked lime, sodium hydroxide or reactive MgO.

In this study, it is aimed to produce slag-based sodium carbonate-activated mixes, having sufficient early age strength and appropriate setting time values. To improve such properties, different amounts (0 - 15%) of reactive MgO were substituted with slag. One-part production method was applied for the mix productions. The consistency, setting time, compressive strength development properties of the produced mixtures were determined, and the microstructure properties were examined by X-ray diffractometry and scanning electron microscope at the age of 28th day.

The findings of the study revealed that substituting reactive MgO resulted in decreased consistency and setting time. However, a significant improvement in compressive strength, particularly at early stages, was observed. The reactive MgO/slag mixtures exhibited satisfactory compressive strength values, which can be attributed to their microstructure properties.