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1、 福建交通职业技术学院教案纸福建交通职业技术学院教案纸 第 页课程： 学年 第_ 1 学期 第 周 月 日教 学 内 容 备 注Unit One CementIntroductionCement, any material that hardens and becomes strongly adhesive after application in plastic form. The term cement is often used interchangeably with glue and adhesive; in engineering and building construction
2、 the term usually refers to a finely powdered, manufactured substance consisting of gypsum plaster or portland cement that hardens and adheres after being mixed with water.Cements are used for various purposes, such as binding sand and gravel together with Portland cement to form concrete, for uniti
3、ng the surfaces of various materials, or for coating surfaces to protect them from chemical attack. Cements are made in a wide variety of compositions for a wide variety of uses. They may be named for the principal constituents, such as calcareous cement, which contains silica, and epoxy cement, whi
4、ch contains epoxy resins; for the materials they join, such as glass or vinyl cement; for the object to which they are applied, such as boiler cement, or for their characteristic property, such as hydraulic cement, which hardens underwater, or acid-resisting cement, or quick-setting cement. Cements
5、used in construction are sometimes named for their commonly reported place of origin, like Roman cement, or for their resemblance to other materials, such as Portland cement, which produces a concrete resembling the Portland stone used for building in England. Cements that resist high temperatures a
6、re called refractory cements.Cements set, or harden, by the evaporation of the plasticizing liquid such as water, alcohol, or oil, by internal chemical change, by hydration, or by the growth of interlacing sets of crystals. Other cements harden as they react with the oxygen or carbon dioxide in the
7、atmosphere.Portland CementTypical Portland cements are mixtures of tricalcium silicate, tricalcium aluminate, and dicalcium silicate, in varying proportions, together with small amounts of magnesium and iron compounds. Gypsum is often added to slow the hardening process.Portland cement is manufactur
8、ed from lime-bearing materials, usually limestone, together with clays, shales, or blast-furnace slag containing alumina and silica, in the approximate proportions of 60 percent lime, 19 percent silica, and 8 percent alumina, 5 percent iron, 5 percent magnesia, and 3 percent sulfur trioxide. Some ro
9、cks, called cement rocks, are naturally composed of these elements in approximately suitable proportions and can be made into cement without the use of large quantities of other raw materials. In general, however, cement plants rely on mixed materials. In the manufacture of cement the raw materials
10、are ground together, the mixture is heated until it fuses into a clinker, and the clinker is ground into a fine powder.A number of tests are used to check the quality of the cement. A common one is to use a mortar specimen of one part of cement and three parts of sand and measure its tensile strengt
11、h after a week in air and underwater. A good cement will show a tensile strength of 19.4 kg per sq cm (2751 b per sq in) under these conditions. Special Cements福建交通职业技术学院教案纸福建交通职业技术学院教案纸 第 页课程： 学年 第_ 1 学期 第 周 月 日教 学 内 容 备 注By varying the percentage of its normal components or adding others, portland
12、 cement can be given various desirable characteristics, such as rapid hardening, low heat during hydration, and resistance to alkalis. Rapid-hardening cements, sometimes called high-early-strength cements, are made by increasing the proportion of tricalcium silicate or by finer grinding, so that up
13、to 99.5 percent will pass through a screen with 16,370 openings per sq cm (105,625 per sq in). Some of these cements will harden as much in a day as ordinary cement does in a month. They produce much heat during hydration, however, which makes them unsuitable for large structures where such heat may
14、 cause cracks. Special low-heat cements, which usually have a large proportion of dicalcium silicate, are generally used for massive pourings. Where concrete work must be exposed to alkaline conditions, which attack concretes made with ordinary portland cement, resistant cements with a low aluminum
15、content are generally employed. Cements for use under salt water may contain as much as 5 percent iron oxide, and those with as much as 40 percent aluminum oxide are used to resist the action of sulfate-bearing waters.简介水泥，是一种物质，在以塑性形式使用后会硬化，成为强烈的粘合剂后。水泥这个术语往往可以和胶水和粘合剂交替使用；在工程和建筑工程，这个术语通常指的是一种细粉末，工厂
16、化生产的一种物质，含有石膏灰分或者波特兰水泥，与水混合会变硬。变粘。水泥用于各种目的，如结合沙和砾石与波特兰水泥形成混凝土，用于连接各种材料表面或表面涂层，保护他们免受化学侵蚀。水泥是由多种成分制造，用于为多种用途。他们可能以主要成分被命名，如石灰水泥，其中包含二氧化硅，环氧水泥，其中包含环氧树脂；也可以以它们加入的材料命名，如玻璃或塑料水泥；为也可以以它们所用于的对象命名，如锅炉水泥，或以他们的特性命名，水硬性水泥，在水的作用下硬化，或耐酸水泥，或速凝水泥。水泥用于建筑，有时以原产地被命名，如罗马水泥，或以其与其他材料的相似点命名，如波特兰水泥，会产生类似波特兰石的混凝土，用于英国建筑。能抵抗高温的水泥被称为耐火水泥
