![]() ![]() ![]() Aspdin’s product may well have been too lightly burned to be a true Portland cement, and the real prototype was perhaps that produced by Isaac Charles Johnson in south eastern England about 1850. He called the product “Portland cement” because of a fancied resemblance of the material, when set, to Portland stone, a limestone used for building in England. The invention of Portland cement usually is attributed to Joseph Aspdin of Leeds, Yorkshire, England, who in 1824 took out a patent for a material that was produced from a synthetic mixture of limestone and clay. Soon afterward in the United States, a similar material was obtained by burning a naturally occurring substance called “cement rock.” These materials belong to a class known as natural cement, allied to Portland cement but more lightly burned and not of controlled composition. The next development, taking place about 1800 in England and France, was a material obtained by burning nodules of clayey limestone. Portland cement is a successor to a hydraulic lime that was first developed by John Smeaton in 1756 when he was called in to erect the Eddy stone Lighthouse off the coast of Plymouth, Devon, England. (The term cement, meanwhile, derives from the Latin word cementum, which meant stone chippings such as were used in Roman mortar-not the binding material itself.) To this day the term pozzolanic, or pozzolan, refers either to the cement itself or to any finely divided aluminosilicate that reacts with lime in water to form cement. Volcanic ash mined near what is now the city of Pozzuoli, Italy, was particularly rich in essential aluminosilicate minerals, giving rise to the classic pozzolanic cement of the Roman era. This formed the cementing material of the Roman mortars and concretes of 2,000 years ago and of subsequent construction work in Western Europe. The materials used were lime and a volcanic ash that slowly reacted with it in the presence of water to form a hard mass. The origin of hydraulic cements goes back to ancient Greece and Rome. Each year almost one ton of concrete is poured per capita in the developed countries. ![]() The products are prefabricated in factories and supplied ready for installation.īecause concrete is the most widely used of all construction materials in the world today, the manufacture of cement is widespread. Portland cement also is used in the manufacture of bricks, tiles, shingles, pipes, beams, railroad ties, and various extruded products. Mixtures of soil and Portland cement are used as a base for roads. Concrete is used for a large variety of constructional purposes. Mortars are used for binding bricks, blocks, and stone in walls or as surface renderings. Concrete is a mixture of cement, sand or other fine aggregate, and a coarse aggregate that for most purposes is up to 19 to 25 mm ( 3/ 4 to 1 inch) in size, but the coarse aggregate may also be as large as 150 mm (6 inches) when concrete is placed in large masses such as dams. Mortar is cement mixed with sand or crushed stone that must be less than approximately 5 mm ( 3/ 16 inch) in size. Construction cements share certain chemical constituents and processing techniques with ceramic products such as brick and tile, abrasives, and refractories.Ĭements may be used alone (i.e., as grouting materials), but the normal use is in mortar and concrete in which the cement is mixed with inert material known as aggregate. The focus is on Portland cement, but attention is also given to other types, such as slag-containing cement and high-alumina cement. This article surveys the historical development of cement, its manufacture from raw materials, its composition and properties, and the testing of those properties. The most important of these is Portland cement. Because of their hydrating properties, constructional cements, which will even set and harden under water, are often called hydraulic cement. Setting and hardening result from hydration, which is a chemical combination of the cement compounds with water that yields sub microscopic crystals or a gel-like material with a high surface area. Cements of this kind are finely ground powders that, when mixed with water, set to a hard mass. Cement in general, adhesive substances of all kinds, but in a narrower sense the binding materials used in building and civil engineering construction. ![]()
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