Date

2022-2

Author

Ardoğa, Mehmet Kemal

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Magnesium oxide (MgO) has limited use in civil engineering applications. The presence of MgO (especially in free form) in portland cements is limited by the standards due to the risk involved in the gradual hydration of MgO that may lead to disruptive expansions after the cementitious system hardens. However, it is possible to overcome this detrimental effect by calcining magnesite at lower temperatures than that is encountered in the cement kilns and use thus obtained reactive MgO as an additive in cement. In this case, MgO will react with water to form magnesium hydroxide (brucite) while the cementitious system is still plastic. Later, brucite will carbonate to reform magnesium carbonates. In this study, firstly the synthesis of reactive magnesia from naturally – obtained magnesite was carried out at different calcination temperatures. Then the magnesia obtained was blended with CEM I and CEM II cements in varying amounts (15-50%, by mass). The cements thus obtained were studied comparatively with the control cements without reactive MgO from hydration reactions, strength, and durability characteristics points of view. It was found that the most reactive magnesia was obtained with the curing regime including 600 °C of burning temperature and 120 minutes of exposure time. It was also determined that the reactive magnesia caused a reduction in compressive strength when cured in ambient conditions. However, generally, when cured in a carbon dioxide environment, the compressive strengths increased with increasing carbon dioxide concentration.

Subject Keywords

Cement, Magnesium oxide, Hydration, Carbonation

URI

https://hdl.handle.net/11511/96328

Collections

Graduate School of Natural and Applied Sciences, Thesis