Abstract: A process for preparing calcium silicate articles having a bulk density of 0.3 to 0.9 g/cm.sup.3 including the steps of mixing a major portion of calcium silicate and minor portions of anhydrous calcium aluminosilicate or its analogue, a reinforcing fiber and a polymer binder in water to give an aqueous slurry, molding the slurry into a desired for, and drying the molded slurry at 100.degree.-180.degree. C.

Abstract: The specification discloses a novel calcium silicate water-treating agent exhibiting a superior ability to remove various kinds of phosphorus compounds or other environmental pollutants contained in wastewater, the calcium silicate water treating agent comprising a burned product which is prepared by burning a mixture containing as main constituents calcium compound, thermally decomposable to calcium oxide (CaO), and SiO.sub.2 -containing compound at a temperature of 1300.degree. to 1600.degree. C., the molar ratio of CaO/SiO.sub.2 of the resultant burned product being in the range of 1.5 to 5.0, preferably 2.0 to 4.0. In this water treating agent, SiO.sub.2 component may be partially replaced by Al.sub.2 O.sub.3 and/or Fe.sub.2 O.sub.3. A further water treating agent is prepared by heating the hydrate of the burned product prepared above at a temperature of 50.degree. to 700.degree. C.