An increasing trend in fireproofing construction projects demands construction materials that are in compliance with fire rating regulations; magnesium oxychloride (MOC) is a ceramic material with significant fire resistance properties that has the potential to serve as an alternative to modern construction materials for passive fire protection systems and structural applications. Despite many advantages, this material has shortcomings that include a lack of understanding of the chemistry involved in manufacture and inconsistent weathering stability. For example, the material can undergo a transformation to magnesium hydroxide, losing its advantageous properties. Our research goal is to elucidate the chemical reactions involved in the formation of MOC and the mechanisms by which the degradation transformation occurs. The broader impact is to form a high-quality, weather-stable structural material. The MOC formation reaction mechanism was investigated using time-resolved quantitative x-ray diffraction. The reaction was found to be a two-step process consisting of magnesium oxide dissolution into an amorphous phase followed by a crystallization process. Additionally, the kinetic effects of the temperature and surface area of the magnesium oxide were explored for both reaction steps. The activation energies of the MOC crystallization and magnesium oxide consumption were found to be 35.6 kJ/mol and 33.5kJ/mol respectively. These results were used to accurately predict curing times on an industrial scale. Weathering stability of crystalline MOC was found to increase when exposed to CO2 at 500 psi. Using x-ray diffraction and scanning electron imaging, it was concluded that MOC partially reacts with CO2 to form a chlorartinite, a compound that withstands weathering conditions but does not compromise structural integrity. Crystal size was also found to decrease during this process; it is thought that this increases the surface tension of the overall crystal structure, contributing to the stability.

Synthesis and characterization of magnesium oxychloride as a fire resistant construction material

253rd National Meeting (2017)

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