Composite gypsum board and methods related thereto

A composite gypsum board comprising:

• (a) a board core comprising set gypsum formed from at least water and stucco, the board core having a dry density, the core defining first and second core faces in opposing relation;
• and
• (b) a concentrated layer formed from at least water, stucco, and uncooked, non-migratory, strength-enhancing starch as an enhancing additive, the concentrated layer disposed in bonding relation to the first core face;
• (i) the concentrated layer having a concentration of the enhancing additive that is greater than zero and at least 2.5 times a concentration of enhancing additive, if any, used in forming the board core,
• (ii) the board core having a dry density of about 30 pcf or less, and
• (iii) the concentrated layer having a dry thickness between about 0.05 and about 0.23 cm, and the concentrated layer having a higher dry density than the board core dry density,
• (iv) the composite gypsum board having a nail pull resistance according to ASTM C473-10, Method B of at least 72 lbs. of force,
• (v) the board core forms at least 80% of the bulk volume of the board, and
• (vi) the composite gypsum board has a dry density of about 33 pcf (about 530 kg/m3) or less, wherein a ratio of the nail pull resistance to the dry density of the composite gypsum board is at least 2.18:1.

A composite gypsum board comprising:

• (a) a board core comprising set gypsum formed from at least water, stucco, and no strength-enhancing starch as an enhancing additive, the board core having a dry density, the core defining first and second core faces in opposing relation;
• and
• (b) a concentrated layer formed from at least water, stucco, optionally one or both of polyphosphate and dispersant, and -uncooked, non-migratory, strength-enhancing starch as an enhancing additive, the concentrated layer disposed in bonding relation to the first core face;
• (i) the composite gypsum board having a nail pull resistance according to ASTM C473-10, Method B of at least 72 lbs. of force,
• (ii) the board core forms at least 80% of the bulk volume of the composite gypsum board,
• (iii) the composite gypsum board has a dry density of about 33 pcf (about 530 kg/m3) or less, wherein a ratio of the nail pull resistance to the dry density of the composite gypsum board is at least 2.18:1, and
• (iv) the concentrated layer having a dry thickness between about 0.05 and about 0.23 cm.

A composite gypsum board comprising:

• (a) a board core comprising set gypsum formed from at least water and stucco, the board core defining a first core face;
• and
• (b) a concentrated layer formed from at least water, stucco, and an enhancing additive including uncooked, non-migratory, strength-enhancing starch, the concentrated layer disposed in bonding relation to the first core face;
• (i) the concentrated layer having a concentration of the enhancing additive that is greater than zero and at least 2.5 times the concentration of the enhancing additive, if present, in the board core,
• (ii) the concentrated layer having a dry thickness between about 0.05 and about 0.23 cm, and the board core having a dry thickness greater than the thickness of the concentrated layer,
• (iii) the concentrated layer having an average core hardness that is at least 1.5 times greater than the average core hardness of the board core,
• (iv) the composite gypsum board having a nail pull resistance according to ASTM C473-10, Method B, of at least 72 lbs. of force,
• (v) the board core forming at least 80% of the bulk volume of the composite gypsum board,
• (vi) the composite gypsum board having a dry density of about 33 pcf (about 530 kg/m3) or less, wherein the ratio of the nail pull resistance to the dry density of the composite gypsum board is at least 2.18:1, and
• (vii) the concentrated layer further including paper fibers, mineral fibers, carbon fibers, nano-cellulose fibers, micro-cellulose fibers, or a combination.