Process and apparatus for manufacturing set cellular cement

A continuous process for manufacturing set cellular cement, comprising the steps of:

• (i) mixing a cementitious material, water, a foaming agent, a retarder, an accelerator and optionally additives in a primary mixer under high-shear mixing conditions, an amount of the foaming agent being 0.01 to 1 g/l of slurry, an average residence time being 1 to 10 seconds, and the peripheral speed being at least 400 m/min, into a free flowing slurry having a slump of at least 100 mm, wherein the primary mixer is an inclined disc mixer;
• subsequently
• (ii) injecting air by a nozzle in a secondary mixer under controlled-shear mixing conditions, the peripheral speed being lower than the high-shear mixing conditions of step (i), into the slurry of step (i) and distributing air through the slurry to form a cellular slurry, wherein the secondary mixer comprises a tee for receiving the slurry through a first pipe and air through a second pipe;
• subsequently
• (iii) casting said cellular slurry of step (ii);
• and
• (iv) finally allowing said cellular slurry to set,
• in which the cementitious material is calcium sulfate α-hemi-hydrate, calcium sulfate β-hemi-hydrate or a blend thereof, and the final set product has a core density between 200 and 1100 kg/m3,
• wherein a water/plaster ratio of the slurry is 0.65 to 1.05 by weight, the plaster being the cementitious material.