disadvantages are avoided.
These objects are attained, in accordance with the invention, in a method of preparing a porous paste which comprises the steps of:
(a) introducing a paste-forming binder and mixing water forming a settable composition with the binder into a mixing chamber;
(b) mixing the binder and water to form a settable composition by displacing at least one mixing member in the chamber relative to chamber walls defining the mixing chamber; and
(c) during displacement of the at least one mixing member introducing a pore-forming gas into the composition at a supply pressure above a pressure in the chamber through at least one fine-porous element forming at least a segment of at least one of the walls, thereby forming the porous paste.
The mixer for producing the porous paste can comprise:
adisk-shaped chamber provided with a peripheral wall and a bottom wall;
means for introducing a paste-forming binder and mixing water forming a settable composition with the binder into the mixing chamber;
a mixing disk rotatable in the chamber and formed with a peripheral array of teeth for mixing the binder and water to form a settable composition; and
a fine-porous element forming at least a segment of at least one of the walls and bounding the chamber on one side and a pressurizable compartment on an opposite side for introducing a pore-forming gas into the composition at a supply pressure above a pressure in the chamber during rotation of the mixing disk, thereby forming the porous paste.
In the method of the invention for producing a porous paste or slurry, especially where