The differences in the types of gypsum are related to the amount of water removed, resulting in varying densities and particle sizes of the material. It is the calcination process that determines the strength of the gypsum material. Plaster and stone are products of the dehydration process. Calcination is the process of heating the gypsum to dehydrate it (partially or completely) to form calcium sulphate hemihydrate. Fambrini & Daniels Cast stone manufacturers.Gypsum (calcium sulphate dihydrate) is a naturally occurring mineral used in dentistry to fabricate models ( Figure 12.1a), casts and dies ( Figure 12.1b).The European Commission's "Construction Products Regulations" legislation states that by mid-2013 CE marking becomes mandatory for certain construction products sold in Europe, including some Cast Stone items". In the UK and Europe, it is more normal to use the Standard "BS 1217 Cast stone - Specification" from the BSI Group. The ASTM process ensures that interested individuals and organizations representing industry, academia, consumers, and governments alike, all have an equal vote in determining a standard's content. The ASTM method of developing standards has been based on consensus of both users and producers of all kinds of materials. Membership in ASTM International (founded in 1898 as the American Chapter of the International Association for Testing and Materials and most recently known as the American Society for Testing and Materials) exceeds 30,000 technical experts from more than 100 countries who comprise a worldwide standards forum. In the US and some other countries, the industry standard today for physical properties and raw materials constituents is ASTM C 1364, the Standard Specification for Architectural Cast Stone. In dry tamp mixtures molds can be used many times, but in wet cast mixtures molds only can be used once. In the wet cast method, to flow material easily on the mold mixture of integrally colored with water and plastic is used. The dry stone consists of two layers, an inner layer of concrete and an outer layer of decoration which is also known as the facing layer. A low slump mixture is required for the dry tamp method that should be tamped into the mold. Wood, plaster, glue, sand, sheet metal, and gelatin are the molding materials that are used to manufacture drawing work and casting molds like delineate section, bed, and face templates. Both methods manufactured a simulated natural cut stone look. Manufacturing Ĭast stone is commonly manufactured by two methods, the first method is the dry tamp method and the second is the wet cast process. Many manufacturers turned out a very non-porous product able to resist corrosive sea air and industrial and residential air pollution. After setting the blocks are placed in a solution of silicate of soda to indurate and harden them. Powell the firm was broken up in 1828, and the moulds sold to a sculptor, Felix Austin.Īnother well-known variety was Victoria stone, which is composed of three parts finely crushed Mount Sorrel (Leicestershire) granite to one of Portland cement, carefully mechanically mixed and filled into moulds. Having later gone into partnership with a Mr. In engineering projects, it allows transporting the bulk materials and casting near the place of use, which is cheaper than transporting and carving very large pieces of stone.Īccording to Rupert Gunnis a Dutchman named Van Spangen set up an artificial stone manufactury at Bow in London in 1800. It is cheaper and more uniform than natural stone, and widely used. Today most artificial stone consists of fine Portland cement-based concrete placed to set in wooden, rubber-lined fiberglass or iron moulds. One of the earliest developments in the industry was Coade stone, a fired ceramic form of stoneware. Cast stone was first used extensively in London in the 19th century and gained widespread acceptance in America in 1920. The earliest known use of cast stone dates from about 1138 in the Cité de Carcassonne, France. Cast stone may replace such common natural building stones as limestone, brownstone, sandstone, bluestone, granite, slate, coral, and travertine. Cast stone can be made from white and/or grey cements, manufactured or natural sands, crushed stone or natural gravels, and colored with mineral coloring pigments. It is used for architectural features: trim, or ornament facing buildings or other structures statuary and for garden ornaments. The Coade stone South Bank Lion at the south end of Westminster Bridge, LondonĬast stone or reconstructed stone is a highly refined building material, a form of precast concrete used as masonry intended to simulate natural-cut stone.
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