The word "cement" can be traced back to the Ancient Roman term opus caementicium, used to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. It is resistant to attack by chemicals after setting. Rather, it sets as it dries and reacts with carbon dioxide in the air. Non-hydraulic cement (less common) does not set in wet conditions or under water. The chemical process for hydraulic cement was found by ancient Romans who used volcanic ash ( pozzolana) with added lime (calcium oxide). This allows setting in wet conditions or under water and further protects the hardened material from chemical attack. The chemical reaction results in mineral hydrates that are not very water-soluble and so are quite durable in water and safe from chemical attack.
Hydraulic cements (e.g., Portland cement) set and become adhesive through a chemical reaction between the dry ingredients and water. Ĭements used in construction are usually inorganic, often lime or calcium silicate based, which can be characterized as hydraulic or the less common non-hydraulic, depending on the ability of the cement to set in the presence of water (see hydraulic and non-hydraulic lime plaster). Concrete is the most widely used material in existence and is behind only water as the planet's most-consumed resource. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete.
Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate) together. Cement block construction examples from the Multiplex Manufacturing Company of Toledo, Ohio, in 1905Ī cement is a binder, a chemical substance used for construction that sets, hardens, and adheres to other materials to bind them together.
0 kommentar(er)
