土木工程英语教案.docx

1、土木工程英语教案Unit One CementIntroduction Cement, 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 the term usually refers to a finely powdered, manufact

2、ured 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 uniting the surfaces of various materials, or for coating s

3、urfaces 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, which contains epoxy resins; for the materials they join,

4、 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 used in construction are sometimes named for their com

5、monly 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 are called refractory cements. Cements set, or harden,

6、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 atmosphere. Portland Cement Typical Portland cements

7、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 manufactured from lime-bearing materials, usually limestone,

8、 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 rocks, called cement rocks, are naturally composed o

9、f 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 are ground together, the mixture is heated until i

10、t 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 strength after a week in air and underwater. A good ceme

11、nt will show a tensile strength of 19.4 kg per sq cm (2751 b per sq in) under these conditions. Special Cements By varying the percentage of its normal components or adding others, portland cement can be given various desirable characteristics, such as rapid hardening, low heat during hydration, and

12、 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 to 99.5 percent will pass through a screen with 16,370 openings per sq cm (105,625 per sq in). Some of these ce

13、ments 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 cause cracks. Special low-heat cements, which usually have a large proportion of dicalcium silicate, are gener

14、ally 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 content are generally employed. Cements for use under salt water may contain as much as 5 percent iron oxide, a

15、nd 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

16、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。水泥凝固或硬化，是通过蒸发塑化液体比如水，酒精，或油，通过内部的化学变化，水化作用，或晶体交织凝固作用的增长实现的。其他水泥当他们与氧气或大气中的二氧化碳发生反应时硬化。波特兰水泥典型的波特兰水

17、泥是不同的比例的硅酸三钙，铝酸三钙，和硅酸二钙以及少量镁和铁的化合物的混合物。石膏是经常添加减缓硬化过程。波特兰水泥是用含石灰的材料制成，通常是石灰岩，连同粘土，页岩，或含氧化铝和二氧化硅的高炉矿渣，以60%的石灰，19%的二氧化硅8%的氧化铝，5%的氧化铁，5%的氧化镁和3%的氧化硫的近似比例。一些岩石，称为水泥石，天生是由这些元素在大约相当比例下组成的，可以制成水泥，不需要大量使用其他原材料。然而，一般来说，水泥厂依靠混合材料。制造水泥的原材料一起混合后被加热到融合成熟料，熟料在磨成细粉。一些测试是用来检查水泥质量。常见的一种是测量用一分水泥和三分的沙子制成的砂浆标本在空气和水中养护一周后

18、的抗拉强度，好的水泥在这些条件的坑拉强度为19.4公斤/平方厘米（2751每平方英寸）。特种水泥通过改变正常组成部分的比例，或者添加替他的成分，波特兰水泥可具有不同的理想的特点，如快速硬化，低水化热，和抗碱。快硬水泥，有时被称为早强水泥，是通过增加硅酸三钙的比例或更细的研磨，使多达百分之99.5的成分将通过一个每平方厘米有16370个筛孔的筛网。其中的一些水泥将在1天内硬化，而普通水泥则需要一个月。他们在水化过程中产生大量的热，但是，这使得它们不适合大型结构，这种热量可能导致裂缝。特殊低热水泥，通常有一个硅酸二钙的大的比例，一般用于大规模浇筑。在具体工作中必须暴露在碱性条件下，这种条件会腐蚀有

19、普通波特兰水泥混凝土，通常使用含少量铝的耐碱水泥。用于盐水条件下的水泥可含有高达百分之5的铁氧化物，那些有高达百分之40的氧化铝的水泥是用来抵御含硝酸的水的作用。AggregatesAggregate is inert material (chemically inactive) such as sand，slag，pebbles, gravel, broken stone, broken bricks, industrial by products etc., which is mixed with cement and water and concrete or mortar is pre

20、pared. The aggregate is added to cement paste to increase the bulk Seventy to seventy-five percent of the volume of the hardened mass of concrete consists of aggregates. The remaining thirty to twenty five percent consists of hardened cement paste, uncombined water (i.e., water not involved in the h

21、ydration of the cement) and air voids. (2)Aggregate must be clean, dense,hard,durable,structurally sound,capable of developing good bond with cement, weather resistant and unaffected by water. )Sand. gravel and broken stone are natural available materials most commonly used as aggregates. Blast furn

22、ace slag (air-cooled and crushed) and broken bricks are the artificial and processed aggregates used in concrete. Natural aggregates are generally classified as coarse and fine aggregates. Natural materials having uniform shear strength in all directions are ideal for use as aggregates. Other natura

23、l materials having pronounced planes of weakness or cleavage (e.g., slate, shale,and micaceous materials) are usually undesirable. The aggregates used for concrete should conform to IS:383-1970 (specifications for coarse and fine aggregate from natural sources for concrete). Coarse aggregate Broken

24、stones, pebbles and gravel retained on IS:4.75 mm sieve is called as coarse aggregate. Coarse aggregate is prepared by crushing igneous stone (e.g., granite, gneiss), sedimentary stone (e.g., sand stones), and metamorphic stone (e.g., crystalline lime). f3Koarse aggregates prepared from very fine gr

25、ained granite stone is used for high strength concrete. Coarse aggregates obtained from crushing of hard sand stone are also suitable for use in concrete, Coarse aggregates made from the soft sand stone cracks when there is high degree of shrinkage in concrete, and it should be used with care. Coars

26、e aggregates (if prepared from close grained crystalline lime stone) is also suitable for use in plain cement concrete. Coarse aggregate made from broken bricks is also used for plain cement concrete only. It makes the concrete weak in strength. In structural concrete, the reinforcement is likely to

27、 be rusted when the broken brick aggregates are used. Coarse aggregates are separated in two or three size groups for use in concrete for large and important constructions. Each size group of aggregate is separately weighed according to grade charts and then combined to result in densely packed conc

28、rete. For construction of less importance, aggregates brought from the pits or river beds (called as all in aggregate) are directly used. Fine aggregate Sand and any other aggregates which pass through IS: 4.75 mm sieve is called fine aggregate. Sand is brought from lakes, pits, rivers and sea-shore

29、s. (4)gand is thoroughly washed so that there remain no clay films over the surface of the aggregate. It prevents adhesion ofcement to the aggregate. Clay and silt are fine materials which pass through 75 micron IS: sieve. Clay and silt materials (if present) will increase water content. Dust is als

30、o detrimental material to concrete. As such the fine aggregates should be free from dust, organic impurities and silts. Chlorides (present in seashore sand) cause efflorescence and rusting and corrosion of reinforcement in structural concrete. In order to prepare strong concrete, angular grained san

31、d (having good interlocking property) is used. Round grained particles of sand lack in interlocking property. In order to prepare the concrete to have good strength, weather resistance and durability, the aggregates are closely packed. For this reason, the gradation of particle sizes of the aggregat

32、es is of considerable importance. Grading of aggregates (5)Gradation of particle sizes of the aggregate vary with the nature and course of material and the requirements in this respect depend upon the type of structure. The particle sizes of fine and coarse aggregates are properly graded. Use of wel

33、l graded aggregates reduces the air voids. The cement fills up the air voids of fine aggregates. The cement and sand both together fill up the air voids of the coarse aggregate. The finishing, workability and uniformity of concrete are considerably affected by the grading of fine aggregates. 集料（1）集料是惰性材料（化学活性不灵敏）如沙，渣，卵石，砾石，碎石，碎砖，工业产品等