Cast Stone Concrete

Cast stone has been a prime building material for hundreds of years. The earliest known use of cast stone dates about to the year 1138 at Carcassonne, France, the city which contains the finest remains of medieval fortification in Europe. Cast stone was first used extensively in London in the 19th century and gained widespread acceptance in America in 1920.
Some researchers have even speculated that the Egyptian pyramids were formed using a form of cast stone, rather than from cut blocks

Cast stone is a concrete masonry product simulating natural cut stone, it is used in architectural applications. Cast stone is used for architectural features: trim, or ornament, for facing buildings or other structures, and for garden ornaments. 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. Cast stone may replace natural cut limestone, brownstone, sandstone, bluestone, granite, slate, coral rock, travertine and other natural building stones.

Cast stone frequently is produced with a low water-to-cement ratio mixture with a "dry" (or "earth moist") consistency. The mixture is consolidated into a mould using an air-driven, or electric, tamping device or vibration under pressure, which is much like the formation of natural sedimentary rock. Products manufactured in this manner are referred to as vibrant-dry-tamped (VDT) cast stone. For cast stone mixtures produced with a slumpable consistency mixture, the concrete typically is consolidated using internal or external vibration applied to the production mould, or increasingly by the use of self-compacting additives.

Over the last decade, new types of admixtures have been developed for VDT concrete products. These new admixtures do not normally work with "wet cast" concrete. These new plasticizers are more efficient than using air-entraining agents to increase compaction in VDT concrete. Some plasticizers have chemical properties that react with the cement to increase ultimate strengths of semi-dry concrete. Another important type of admixture for VDT concrete is integral waterproofing formulas. Tests have shown that some of these integral waterproofing admixtures have improved strength by as much as 20% while reducing the absorption by 40%. The increased strength and reduced absorption results in improved freeze/thaw durability.

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