A cement is a binder, a substance used for construction that sets, hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel (aggregate) together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel, produces concrete [混凝土]. Concrete is the most widely used material in existence and is behind only water as the planet's most-consumed resource.

“鼠标加水泥”的说法是错误的。首先水泥是cement，concrete是混凝土。其次concrete取“实体”之意。有些互联网人不装。

Cements used in construction are usually inorganic, often lime or calcium silicate [硅酸盐] based, which can be characterized as non-hydraulic [在水中凝固的] or hydraulic respectively, depending on the ability of the cement to set in the presence of water (see hydraulic and non-hydraulic lime plaster).

Non-hydraulic cement does not set in wet conditions or under water. Rather, it sets as it dries and reacts with carbon dioxide in the air. It is resistant to attack by chemicals after setting.

Hydraulic cements (e.g., Portland cement) set and become adhesive due to a chemical reaction between the dry ingredients and water. The chemical reaction results in mineral hydrates [水合物] that are not very water-soluble and so are quite durable in water and safe from chemical attack. This allows setting in wet conditions or under water and further protects the hardened material from chemical attack. The chemical process for hydraulic cement was found by ancient Romans who used volcanic ash (pozzolana) with added lime (calcium oxide).

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. The volcanic ash and pulverized [磨成粉或捣成末] brick supplements that were added to the burnt lime, to obtain a hydraulic binder, were later referred to as cementum, cimentum, cäment, and cement. In modern times, organic polymers [聚合物] are sometimes used as cements in concrete.

A polymer is a chemical compound that has a simple structure of large molecules.

Perhaps the earliest known occurrence of cement is from twelve million years ago. A deposit of cement was formed after an occurrence of oil shale [页岩] located adjacent to a bed of limestone burned due to natural causes. These ancient deposits were investigated in the 1960s and 1970s.

Lime (calcium oxide) was used on Crete and by the Ancient Greeks. There is evidence that the Minoans of Crete [克里特岛的米诺斯人] used crushed potsherds [陶器碎片] as an artificial pozzolan for hydraulic cement. Nobody knows who first discovered that a combination of hydrated non-hydraulic lime and a pozzolan produces a hydraulic mixture, but such concrete was used by the Ancient Macedonians [古马其顿人], and three centuries later on a large scale by Roman engineers.

A shard/sherd is a sharp piece of broken glass, metal etc.

Portland cement, the most common type of cement in general use around the world as a basic ingredient of concrete, mortar [砂浆; 灰浆], stucco [灰泥], and non-speciality grout, was developed in England in the mid 19th century, and usually originates from limestone. James Frost produced what he called "British cement" in a similar manner around the same time, but did not obtain a patent until 1822.

Stucco is a type of plaster used for covering walls and decorating ceilings.

Grout is a thin mixture of sand, water, and cement or lime, which is used to fill in the spaces between tiles that are fixed to a wall.

六级/考研单词: cement, construct, adhere, bind, seldom, aggregate, planet, limelight, calcium, respective, carbon, dioxide, ingredient, durable, farther, volcano, ash, oxide, trace, resemble, crush, supplement, organism, compound, molecule, million, deposit, adjacent, investigate, frost, patent, tile