Production of magnesium oxychloride cement boards

A process for making a magnesium oxychloride cementitious construction material, the process comprising:

• forming a magnesium oxychloride concrete mixture into a plurality of boards on a plurality of supports;
• conveying the plurality of supports with the boards thereon through a curing oven, the curing oven comprising an entrance, an exit and a plurality of curing zones therebetween through which the supports with the boards thereon are conveyed, each curing zone having one or more curing air inlets and one or more curing air outlets through which curing air is circulated in contact with the boards when conveyed through the zone, wherein as the boards are conveyed through the curing zones the magnesium oxychloride mixture of the boards is cured to form the magnesium oxychloride cementitious construction material comprising magnesium oxychloride crystals and the time required for each board to pass through the curing oven and the temperature and humidity of the curing air are controlled such that boards exiting the curing oven:
• comprise 5-phase magnesium oxychloride having the formula Mg3(OH)5Cl.4H2O in a concentration of at least about 65 wt %, at least about 70 wt %, at least about 72 wt %, at least about 74 wt %, at least about 76 wt %, at least about 78 wt %, at least about 80 wt %, at least about 82 wt %, at least about 84 wt %, at least about 86 wt %, at least about 88 wt %, or at least about 90 wt %, as determined by X-Ray Diffraction (XRD);
• and/or
• exhibit a flexural strength of at least about 5 MPa, at least about 6 MPa, at least about 10 MPa, or at least about 16 MPa;
• and/or
• a specific flexural strength of at least about 6 MPa/(g/cm3), at least about 10 MPa/(g/cm3), at least about 15 MPa/(g/cm3), or at least about 20 MPa/(g/cm3).

A process for making a magnesium oxychloride cementitious construction material, the process comprising:

• mixing and reacting a source of magnesium chloride brine with a source of magnesium oxide in a premixer, thereby forming a magnesium oxychloride cement premix;
• transferring the magnesium oxychloride cement premix to a mixer;
• mixing the magnesium oxychloride cement premix with an aggregate in the mixer, thereby forming a magnesium oxychloride concrete mixture;
• continuously forming the magnesium oxychloride concrete mixture into a planar mass of the desired dimensions for board production onto a plurality of supports and cutting the planar mass into boards of the desired length;
• and
• continuously conveying the supports with the boards thereon through a curing oven, the curing oven comprising an entrance, an exit and a plurality of curing zones therebetween through which the supports with the boards thereon are conveyed, each curing zone having one or more curing air inlets and one or more curing air outlets through which curing air is circulated in contact with the boards when conveyed through the zone, wherein as the boards are conveyed through the curing zones, the magnesium oxychloride mixture of the boards is cured to form the magnesium oxychloride cementitious construction material comprising magnesium oxychloride crystals.