Cement Forming
Cement, a binding substance used in construction, was invented separately by the Egyptians, Greeks and Babylonians. Each of these ancient civilizations used lime to create mortar for hydraulic cement. Additional groups, including the Aztecs, used cement to build fences, walls and sections of buildings, but modern terminology for cement resides with the Romans who called their masonry work “opus caementitium” because made from crushed rock and burnt lime binder. Using the knowledge of older civilizations, the Romans made cement from pozzolanic ash, which is an alumnio-siliceous material that allows lime and water to bind at room temperature.
As volcanic ash and other additives, the name of the substance morphed to cementum, cimentum, cäment and cement. Cement, as it is known today, is primarily used to make Portland cement, which was first patented in 1824 by Joseph Aspdin. Portland cement is a mixture of clay, limestone and gypsum that makes hydraulic cement used in modern construction. These ingredients are heated to temperatures that cause the formation of a new compound, which the inventors called artificial rock because it looked like stone in Portland Peninsula of Dorset County and the Channel Coast of England.
Joseph Aspdin’s son, William, began producing Portland cement in 1843 claiming it was superior to Roman cement because it was sintered during the sintering process, which heats the material below its melting point to cause adhesion. Similarly, today cement is a combination of oxides created by heating calcium-rich limestone with silicon sand in a kiln until it starts to sinter and forms a substance known as clinker. Clinker burnt in these rotary kilns is then ground in a finishing mill with one of various types of sulfate. The result is a cement powder that, when hydrated, becomes a durable solid.
Cement is used throughout the world in precast concrete forms; concrete is the most common man-made material in construction. Approximately 10-15% of concrete is made from cement powder. Other concrete ingredients include aggregates, water and optional admixtures. Aggregates can range from fine sand to coarse crushed stone, depending on budget and desired finish. The water added for concrete is carefully measured to ensure a proper ratio, which determines final concrete integrity.
Organic and artificial admixtures can be integrated (after the cement percentage has been determined) for strengthening, air-entraining, coloring, accelerating, retarding and plasticizing. Such additions produce desired characteristics in the finalized concrete. Silica fume, a reactive pozzolan, increases concrete durability. Air bubbles disperse in concrete to protect against freezing and thawing conditions. Iron ore oxide pigments tint the color of the concrete for an aesthetically matching hue. Accelerators increase the rate at which the concrete hardens while retardants decrease that rate. Plasticizers improve concrete workability during placement. Substances, such as fly ash, which is ground granulated blast-furnace slag, can be used to replace portions of the cement powder.
Cement Blocks
Many concrete masonry units (CMU) are derived from cement. The most common of these is cement block. Cement, or concrete blocks are used in the manufacturing of split face block, a common element in many cement walls today.
Cement Fences, Fencing and Walls
Cement is used quite often in the contruction of fences and walls. AFTEC specializes in manufacturing forms for cement into which the cement is poured into the precast forms. The cement forms make precast fence walls that are far superior than the competition and can even make textures such and stone, rock, slate, and concrete stucco walls. |
