Fire-resistant gypsum boards and sustainable methods for production thereof

A method of making gypsum board, the method comprising:

• (a) mixing a core slurry comprising stucco, water, colloidal silica, and silica fume;
• (b) placing the slurry between two cover sheets to form a board precursor;
• (c) allowing the slurry in the precursor to set to form the board;
• and
• (d) cutting the board;
• the gypsum board having a High Temperature Shrinkage (S) of 10% or less in the x-y directions (width-length) when heated to 1560° F. (850° C.), according to ASTM C1795-15.

A gypsum board comprising:

• (a) face and back cover sheets;
• (b) a board core disposed between the face and back cover sheets, the core comprising set gypsum formed from a core slurry comprising water, stucco, and colloidal silica and an optional silica fume;
• (c) a back skim coat layer defining first and second back skim coat faces, the back skim coat formed from a back skim coat slurry comprising water, stucco, an optional silica fume and an optional colloidal silica;
• the back skim coat disposed in bonding relation to the core, the first face of the back skim coat layer facing the back cover sheet, and the second face of the back skim coat layer facing the board core,
• (d) a face skim coat layer defining first and second face skim coat faces, the face skim coat formed from a face skim coat slurry comprising water, stucco, an optional silica fume and an optional colloidal silica;
• the face skim coat disposed in bonding relation to the core, the first face of the face skim coat layer facing the face cover sheet, and the second face of the face skim coat layer facing the board core, wherein the back skim coat slurry and the face skim coat slurry can be the same or different;
• wherein
• (e) the silica fume is present in the core slurry in an amount of from 0% to 10% by weight of the stucco and the colloidal silica is present in the core slurry in an amount of from 0.1% to 10% by weight of the stucco;
• (f) the silica fume is present in the back skim coat slurry and/or the face skim coat slurry in an amount of from 0% to 12% by weight of the stucco, and the colloidal silica is present in the back skim coat layer or face skim coat layer in an amount of from 0.1% to 12% by weight of the stucco;
• and
• wherein the gypsum board has a High Temperature Shrinkage (S) of 10% or less in the x-y directions (width-length) when heated to 1560° F. (850° C.), according to ASTM C1795-15.