Abstract: A method of producing gas concrete. Water, lime, cement and sand are pre-mixed. A calcium sulphate-containing component is subsequently mixed in and a rising agent is later admixed to form a castable mass suitable for making gas concrete by the conventional steps of pouring into a mold, permitting the mass to rise and harden sufficiently to be cut to size, and hydrothermally cured. By following the indicated procedure for making the castable mass, the calcium sulphate-containing component can be advantageously used.

Abstract: A method of producing gas concrete. A castable mass is prepared by mixing water, a lime component including lime having a t.sub.60 value of less than ten minutes, and a sand component. A calcium sulphate-containing component is subsequently admixed and a rising agent, such as aluminum powder, is subsequently admixed. The mass thus prepared is cast into molds and fabricated into gas concrete by the conventional steps of permitting the mass to rise and harden, cutting the hardened material to size, and hydrothermally curing. The process makes possible the use of readily available inexpensive lime material without the disadvantages normally resulting from use thereof.

Abstract: A ceramic composition capable of quick firing to form a stoneware product. The composition contains water, a clay component and a lime component. The clay component is a conventional stoneware clay. The lime component is a hydrothermally cured, highly porous lime-sand product having a major proportion of spherical pores. The lime-sand product can be a conventional lightweight cellular concrete product having a density of 0.4 to 0.8 g/cm.sup.3 and is preferably waste product resulting from the manufacture of lightweight concrete products. The composition is made by grinding the clay and lime-sand product, forming an aqueous slurry of the ground material, drying the slurry, and granulating the dried material. The granulated composition is utilized by pressing to shape, drying, and firing at a temperature of 900.degree. to 1100.degree. C for not more than 6 hours. The material is also suitable for conventional firing schedules.

Abstract: Improved building compositions are prepared by including in CaO-containing components/SiO.sub.2 -containing components admixtures a small amount of chemically precipitates silicic acid containing flourine as an impurity.A steam-cured building material preferably prepared by first pre-grinding sand with the chemically precipitated silicic acid and water, storing the resulting slurry for at least 0.5 hour and then mixing it with the CaO-containing component. The wet grinding and storing steps have been found to have a surprisingly favorable effect on the viscosity of the pumpable sand slurry and on the behavior of the risen mixture at the cutting.