Stabilization of setting times of phosphate-bonded magnesia cements

摘要

A process and product for achieving uniform, stabilized working and setting times for phosphate-bonded magnesia cements, wherein a solid phosphate is mixed with an aqueous ammonium phosphate solution and magnesium oxide to form a cement. The solid phosphate may be provided dry or in a slurry, and may be first mixed with the ammonium phosphate solution or the magnesium oxide. Introduction of the solid phosphate into the cement stabilizes the setting time of the cement, which otherwise may vary from a few minutes to several hours, depending upon the characteristics of the ammonium phosphate solution. The ammonium phosphate solution may be supplied as a 10-34-0 composition that is readily available commercially. In one embodiment of the invention, the solid phosphate is provided as an ammonium phosphate mixture of an 18-46- 0 composition, having an ammonium phosphate content above the solubility limit of ammonium phosphate in water. In another embodiment, dry phosphate is mixed with the magnesium oxide, before the ammonium phosphate solution is added.