Lightweight refractory casting composition and articles made using foamed colloidal silica binder

A porous refractory article made from a porous refractory composition, wherein the porous refractory composition comprises:

• about 3% to about 35% by weight of a foamed colloidal silica binder;
• and
• about 65% to about 97% by weight of a solid refractory component exclusive of the foamed colloidal silica binder;
• wherein the foamed colloidal silica binder includes about 20% to about 70% by weight colloidal silica particles, about 30% to about 80% by weight water, and a synthetic non-protein foaming agent present in a weight ratio to the water of about 1:25 to about 1:500;
• and the foamed colloidal silica binder has a total porosity of about 50% to about 95% by volume, total pore volume of about 0.75 to about 15.0 cm3/gram, and a half-life of at least about 1 hour;
• and
• the porous refractory article has a total porosity of about 25% to about 75% by volume.

A porous refractory article, comprising, based on dry weight:

• about 1.5% to about 30% by weight of a dried foamed colloidal silica binder;
• and
• about 70% to about 98.5% by weight a solid refractory component exclusive of the foamed colloidal silica binder;
• wherein the foamed colloidal silica binder includes colloidal silica particles and a synthetic non-protein foaming agent and, prior to drying, has a half-life of at least about 1 hour;
• and
• the porous refractory article has a total porosity of about 25% to about 75% by volume.