Process for making an ultra stable cementitious construction material

A process of making a cementitious material comprising:

• (i) blending
• a) 29 wt. % to 40 wt. %, based on the final total weight of the cementitious material, of a magnesium oxide dry powder containing 80 wt. % to 98 wt. % of magnesium oxide, the magnesium oxide powder having a surface area of from 5 m2/g to 50 m2/g and an average particle size of from about 0.3 μm to about 90 μm, and wherein more than about 90 wt. % of the particles of the magnesium oxide powder have a particle size of less than or equal to about 40 μm, with
• b) 14 wt. % to 18 wt. %, based on the final total weight of the cementitious material, of an aqueous solution of magnesium chloride, the aqueous solution of magnesium chloride comprising 20 wt. % to 30 wt. % of magnesium chloride,
• and reacting the magnesium oxide and the magnesium chloride to form a liquid suspension;
• (ii) mixing the liquid suspension for from 2 minutes to 10 minutes;
• (iii) adding 0.1 wt. % to 10 wt. %, based on the final total weight of the cementitious material, of a stabilizing material to the mixed liquid suspension, wherein the stabilizing material is:
• 1) an aqueous solution comprising 55 wt. % to 65 wt. % of phosphorous acid (H3PO3);
• or
• 2) an aqueous solution comprising 80 wt. % to 90 wt. % of phosphoric acid (H3PO4);
• (iv) allowing the liquid suspension with the stabilizing material to react for from 1 minute to 4 minutes to form an amorphous phase cementitious material;
• wherein a portion of the amorphous phase cementitious material grows a plurality of crystals, each crystal having a molecular weight of from 280 to 709 and being encapsulated by the amorphous phase cementitious material;
• wherein a majority of the stabilizing material is consumed during curing into a nano-molecular veneer over the crystals while increasing the surface area of the plurality of crystals by 2% to 49%;
• and
• wherein the nano-molecular veneer is insoluble in water and protects the plurality of crystals from degradation in water at temperatures of from 20° C. to 60° C. for from 24 hours to 56 days.