High strength pourable gypsum floor underlayments and methods of providing same

The method of claim I wherein said superplasticizer is selected from the group consisting of naphthalene sulfonates;

• naphthalene sulfonate-formaldehyde condensates;
• calcium lignosulfonate;
• melamine sulfonate-formaldehyde condensates;
• and polycarboxylic acids.

A gypsum-based cementitious sub-floor having a dust-free surface and a compressive strength in the range of about 2500 to 6000 psi, made by a method comprising the steps of

• a) providing a gypsum-based cementitious composition consisting essentially of
• 1) from about 10% to 20%, by total weight of said gypsum-based cementitious composition, hydraulic cement;
• 2) from about 70% to 86%, by total weight of said gypsum-based cementitious composition, calcium sulfate .alpha.-hemihydrate;
• 3) from about 0.5% to 0.75%, by total weight of said gypsum-based cementitious composition, of a superplasticizer;
• 4) from about 0.2% to 0.5%, by total weight of said gypsum-based cementitious composition, of a defoamer;
• and
• 5) from about 0.002% to 0.01. %, by total weight of said gypsum-based cementitious composition, of an alkylcellulose;
• b) mixing said gypsum-based cementitious composition with sand, in a weight ratio to said gypsum-based cementitious composition of from about 1.25:1 to 2.5:1;
• and sufficient water to provide a pumpable, self-leveling wet gypsum-based cementitious composition having a flowability such that when 600 ml of said wet gypsum-based cementitious composition is poured into a 15.2 cm.times.20.3 cm.times.1.9 cm tray at a height of 12.7 cm in one smooth motion, the wet gypsum-based cementitious composition completely self-levels to produce a topographically smooth surface without floating or finishing, and
• c) hardening said wet gypsum-based cementitious composition to provide a sub-floor resistant to dimensional changes caused during hardening and having a dust-free surface and a compressive strength in the range of about 2500 to 6000 psi.

A gypsum-based cementitious composition capable of, upon mixing with sand in a weight ratio to said gypsum-based cementitious composition of from about 1.25:1 to 2.5:1;

• and sufficient water to provide a pumpable, self-leveling wet gypsum-based cementitious composition having a flowability such that when 600 ml of said wet gypsum-based cementitious composition is poured into a 15.2 cm.times.20.3 cm.times.1.9 cm tray at a height of 12.7 cm in one smooth motion, the wet gypsum-based cementitious composition completely self-levels to produce a topographically smooth surface without floating or finishing, providing, upon hardening, a sub-floor resistant to dimensional changes caused during hardening and having a dust-free surface and compressive strength in the range of about 2500 to 6000 psi, said gypsum-based cementitious composition consisting essentially of
• a) from about 10% to 20%, by total weight of said gypsum-based cementitious composition, hydraulic cement;
• b) from about 70% to 90%, by total weight of said gypsum-based cementitious composition, calcium sulfate .alpha.-hemihydrate;
• c) from about 0.5% to 0.75%, by total weight of said gypsum-based cementitious composition, of a superplasticizer;
• d) from about 0.2% to 0.5%, by total weight of said gypsum-based cementitious composition, of a defoamer, and;
• e) from about 0.002% to 0.01%, by total weight of said gypsum-based cementitious composition, of an alkylcellulose.

A wet gypsum-based cementitious composition having a flowability such that when 600 ml of said wet gypsum-based cementitious composition is poured into a 15.2 cm.times.20.3 cm.times.1.9 cm tray at a height of 2.7 cm in one smooth motion, the wet gypsum-based cementitious composition completely self-levels to produce a topographically smooth surface without floating or finishing, providing, upon hardening, a sub-floor resistant to dimensional changes caused during hardening and having a dust-free surface and compressive strength in the range of about 2500 to 6000 psi, said wet gypsum-based cementitious composition consisting essentially of

• a) from about 10% to 20%, by total weight of said gypsum-based cementitious composition, hydraulic cement;
• b) from about 70% to 86%, by total weight of said gypsum-based cementitious composition, calcium sulfate .alpha.-hemihydrate;
• c) from about 0.5% to 0.75%, by total weight of said gypsum-based cementitious composition, of a superplasticizer;
• d) from about 0.2% to 0.5%, by total weight of said gypsum-based cementitious composition, of a defoamer;
• and
• e) from about 0.002% to 0.01%, by total weight of said gypsum-based cementitious composition, of an alkylcellulose;
• f) sand, in a weight ratio to said gypsum-based cementitious composition of from about 1.25:1 to 2.5:1;
• and
• g) sufficient water to provide said flowability.