Abstract: A composition comprising an agricultural fertilizer and pellets is disclosed. The fertilizer and the pellets are predominantly in the minus six plus thirty mesh size. The pellets consist essentially of at least one hydroxide, oxide or carbonate of calcium, magnesium or both, and constitute from 5 to 90 percent by weight of the composition. The pellets contain at least 2 percent by weight of calcium, magnesium or both in the form of the oxide, the hydroxide or both, calculated as the oxide.

Abstract: A method for recovering a magnesium carbonate of high purity from an aqueous magnesium hydroxide slurry is disclosed. The slurry contains at least 1 percent of magnesium hydroxide and consists of water, magnesium hydroxide and impurities normally associated with magnesium hydroxide slurries. The method involves carbonating the slurry with sufficient carbon dioxide to dissolve a substantial proportion of the magnesium hydroxide therein as magnesium bicarbonate, continuing carbonation until a solution saturated with magnesium bicarbonate is formed, a portion of the magnesium bicarbonate is converted to a crystalline magnesium carbonate and substantially all dissolved calcium is precipitated, so that the slurry contains dissolved magnesium bicarbonate, a crystalline magnesium carbonate precipitate and a calcium carbonate precipitate.

Abstract: The recovery of a magnesium carbonate of high purity from an aqueous slurry comprising a mixture of calcium carbonate and hydrated magnesium carbonate is disclosed. Carbon dioxide is introduced into the slurry while the temperature thereof is maintained not higher than about 40.degree. C. to produce an appreciable concentration of magnesium cations in the water of the slurry. Introduction of carbon dioxide is discontinued while most of the calcium is present as the carbonate. Solids are then separated from the aqueous solution of magnesium cations which is produced. Also disclosed is the removal, e.g., by means of a vacuum pump, of carbon dioxide from the aqueous solution of magnesium cations to precipitate magnesium carbonate and the separation of precipitated magnesium carbonate from the aqueous phase.

Abstract: A high compressive strength concrete is disclosed. The concrete is formed by mixing with water a general-use cement, dolomitic limestone as a low-silica manufactured fine aggregate, and from about 5 to 15 percent by weight, based on the manufactured fine aggregate, of a precipitate comprising CaO-MgO from the gaseous effluent from a kiln burning dolomitic limestone, and curing the mixture.