GB427730A - Improvements in bricks, tiles, slabs or the like for building or decorative purposes - Google Patents

Abstract

A cement-sand composition for bricks, tiles, and slabs with a glazed surface, or for use as a glazed surfacing material on concrete or rough brickwork, is prepared by first boiling fine sand in an aqueous solution of an alkaline salt such as carbonates, hydroxides, silicates, aluminates, and phosphates, whereby the particles of silica are coated with a gelatinous silicate before mixing with the cement. The cement may be of the Portland, aluminous, oxychloride, or phosphate variety. Alternatively, the heat for the reaction may be obtained by adding quicklime to the solution. Kaolin, accelerators, and gas liberators may be added. Examples are: (1) 50 galls. fine sand containing 10 per cent of particles of the fineness of flour of natural or precipitated silica, 1 gall. common soda, and 18-19 galls. water are boiled from three to ten hours; 90 lbs. of this treated sand are mixed with 40 lbs. cement, and colouring matter and a small quantity of sulphur added with lukewarm water to form a plastic mass. To remove gases, 2 pints of 10 per cent solution of ammonium chloride are added, with 5 to 15 pints of an accelerator made by dissolving 20 ozs. potash alum in 10 pints water and adding it to 20 ozs. common soda in 10 pints water. The sand mixture stands for five to thirty minutes to gelatinize, and is cast in moulds lined with glass or hard steel. The mixture sets in one to two days in air. The thickness may be increased by a layer of ordinary concrete, and fissures may be imitated by applying streaks or dots of oil on the pallets. For cheaper products, untreated sand may be added to the mix, producing a friable mass for pressed work; (2) 60 lbs. kaolin, 10 lbs. common soda, and 20 galls. water are boiled for several hours; 1 gall. of this solution is mixed for three minutes with 100 lbs. fine sand and 95 lbs. quicklime, and the mass is put in closed silos for twenty-four hours; the heat of hydration raises the temperature to 180 DEG F., and sodium silicate is formed. The treated sand is then mixed with Portland cement in the ratio 8 to 1, and colouring matter may be added; (3) 100 lbs. sand are boiled for one hour with 1 lb. common soda in 2 galls. water, and there are added 1 lb. china clay and 5 lbs. quicklime. After twenty-four hours the mass is made semiplastic with cement; (4) 100 lbs. sand, 5 lbs. quicklime, and 3 lbs. china clay are mixed dry; 1 gall. of 1 per cent aqueous solution of soda is added and mixed for three to five minutes, and after twenty-four hours cement is added as in Example 3.