(84c) Conversion of Magnesium Oxychloride to Chlorartinite with CO2 and Resulting Increased Water Resistance

Magnesium oxychloride cement is a fire resistant structural material with applications in construction as passive fire protection systems. This study examines the conversion of magnesium oxychloride to chlorartinite and resulting improved water resistance. Samples were exposed to CO₂ in a pressure cell to accelerate the formation of chlorartinite on the material surface. The extent of chlorartinite formation correlates with improved water resistance. We hypothesize that a protective semi-insoluble chlorartinite layer forms on the surface of the magnesium oxychloride crystals and improves water stability. Untreated samples convert to magnesium hydroxide when subjected to an accelerated water resistance test (submersion in deionized water at 60 °C for 24 hours). Samples exposed to CO2 show reduced MOC conversion. Chlorartinite was observed to convert to hydromagnesite, magnesium hydroxide and amorphous phase.