土木工程英语教案.docx

土木工程英语教案.docx

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土木工程英语教案

UnitOneCement

Introduction

Cement,anymaterialthathardensandbecomesstronglyadhesiveafterapplicationinplasticform.Thetermcementisoftenusedinterchangeablywithglueandadhesive;inengineeringandbuildingconstructionthetermusuallyreferstoafinelypowdered,manufacturedsubstanceconsistingofgypsumplasterorportlandcementthathardensandadheresafterbeingmixedwithwater.

Cementsareusedforvariouspurposes,suchasbindingsandandgraveltogetherwithPortlandcementtoformconcrete,forunitingthesurfacesofvariousmaterials,orforcoatingsurfacestoprotectthemfromchemicalattack.Cementsaremadeinawidevarietyofcompositionsforawidevarietyofuses.Theymaybenamedfortheprincipalconstituents,suchascalcareouscement,whichcontainssilica,andepoxycement,whichcontainsepoxyresins;forthematerialstheyjoin,suchasglassorvinylcement;fortheobjecttowhichtheyareapplied,suchasboilercement,orfortheircharacteristicproperty,suchashydrauliccement,whichhardensunderwater,oracid-resistingcement,orquick-settingcement.Cementsusedinconstructionaresometimesnamedfortheircommonlyreportedplaceoforigin,likeRomancement,orfortheirresemblancetoothermaterials,suchasPortlandcement,whichproducesaconcreteresemblingthePortlandstoneusedforbuildinginEngland.Cementsthatresisthightemperaturesarecalledrefractorycements.

Cementsset,orharden,bytheevaporationoftheplasticizingliquidsuchaswater,alcohol,oroil,byinternalchemicalchange,byhydration,orbythegrowthofinterlacingsetsofcrystals.Othercementshardenastheyreactwiththeoxygenorcarbondioxideintheatmosphere.

PortlandCement

TypicalPortlandcementsaremixturesoftricalciumsilicate,tricalciumaluminate,anddicalciumsilicate,invaryingproportions,togetherwithsmallamountsofmagnesiumandironcompounds.Gypsumisoftenaddedtoslowthehardeningprocess.

Portlandcementismanufacturedfromlime-bearing'materials,usuallylimestone,togetherwithclays,shales,orblast-furnaceslagcontainingaluminaandsilica,intheapproximateproportionsof60percentlime,19percentsilica,and8percentalumina,5percentiron,5percentmagnesia,and3percentsulfurtrioxide.Somerocks,calledcementrocks,arenaturallycomposedoftheseelementsinapproximatelysuitableproportionsandcanbemadeintocementwithouttheuseoflargequantitiesofotherrawmaterials.Ingeneral,however,cementplantsrelyonmixedmaterials.Inthemanufactureofcementtherawmaterialsaregroundtogether,themixtureisheateduntilitfusesintoaclinker,andtheclinkerisgroundintoafinepowder.

Anumberoftestsareusedtocheckthequalityofthecement.Acommononeistouseamortarspecimenofonepartofcementandthreepartsofsandandmeasureitstensilestrengthafteraweekinairandunderwater.Agoodcementwillshowatensilestrengthof19.4kgpersqcm（2751bpersqin）undertheseconditions.SpecialCements

Byvaryingthepercentageofitsnormalcomponentsoraddingothers,portlandcementcanbegivenvariousdesirablecharacteristics,suchasrapidhardening,lowheatduringhydration,andresistancetoalkalis.Rapid-hardeningcements,sometimescalledhigh-early-strengthcements,aremadebyincreasingtheproportionoftricalciumsilicateorbyfinergrinding,sothatupto99.5percentwillpassthroughascreenwith16,370openingspersqcm（105,625persqin）.Someofthesecementswillhardenasmuchinadayasordinarycementdoesinamonth.Theyproducemuchheatduringhydration,however,whichmakesthemunsuitableforlargestructureswheresuchheatmaycausecracks.Speciallow-heatcements,whichusuallyhavealargeproportionofdicalciumsilicate,aregenerallyusedformassivepourings.Whereconcreteworkmustbeexposedtoalkalineconditions,whichattackconcretesmadewithordinaryportlandcement,resistantcementswithalowaluminumcontentaregenerallyemployed.Cementsforuseundersaltwatermaycontainasmuchas5percentironoxide,andthosewithasmuchas40percentaluminumoxideareusedtoresisttheactionofsulfate-bearingwaters.

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。

Aggregates

Aggregateisinertmaterial（chemicallyinactive）suchassand，slag，pebbles,gravel,brokenstone,brokenbricks,industrialbyproductsetc.,whichismixedwithcementandwaterandconcreteormortarisprepared.TheaggregateisaddedtocementpastetoincreasethebulkSeventytoseventy-fivepercentofthevolumeofthehardenedmassofconcreteconsistsofaggregates.Theremainingthirtytotwentyfivepercentconsistsofhardenedcementpaste,uncombinedwater（i.e.,waternotinvolvedinthehydrationofthecement）andairvoids.

（2）Aggregatemustbeclean,dense,hard,durable,structurallysound,capableofdevelopinggoodbondwithcement,weatherresistantandunaffectedbywater.）Sand.gravelandbrokenstonearenaturalavailablematerialsmostcommonlyusedasaggregates.Blastfurnaceslag（air-cooledandcrushed）andbrokenbricksaretheartificialandprocessedaggregatesusedinconcrete.Naturalaggregatesaregenerallyclassifiedascoarseandfineaggregates.Naturalmaterialshavinguniformshearstrengthinalldirectionsareidealforuseasaggregates.Othernaturalmaterialshavingpronouncedplanesofweaknessorcleavage（e.g.,slate,shale,andmicaceousmaterials）areusuallyundesirable.TheaggregatesusedforconcreteshouldconformtoIS:

383-1970（specificationsforcoarseandfineaggregatefromnaturalsourcesforconcrete）.Coarseaggregate

Brokenstones,pebblesandgravelretainedonIS:

4.75mmsieveiscalledascoarseaggregate.Coarseaggregateispreparedbycrushingigneousstone（e.g.,granite,gneiss）,sedimentarystone（e.g.,sandstones）,andmetamorphicstone（e.g.,crystallinelime）.f3K"oarseaggregatespreparedfromveryfinegrainedgranitestoneisusedforhighstrengthconcrete.Coarseaggregatesobtainedfromcrushingofhardsandstonearealsosuitableforuseinconcrete,Coarseaggregatesmadefromthesoftsandstonecrackswhenthereishighdegreeofshrinkageinconcrete,anditshouldbeusedwithcare.Coarseaggregates（ifpreparedfromclosegrainedcrystallinelimestone）isalsosuitableforuseinplaincementconcrete.Coarseaggregatemadefrombrokenbricksisalsousedforplaincementconcreteonly.Itmakestheconcreteweakinstrength.Instructuralconcrete,thereinforcementislikelytoberustedwhenthebrokenbrickaggregatesareused.Coarseaggregatesareseparatedintwoorthreesizegroupsforuseinconcreteforlargeandimportantconstructions.Eachsizegroupofaggregateisseparatelyweighedaccordingtogradechartsandthencombinedtoresultindenselypackedconcrete.Forconstructionoflessimportance,aggregatesbroughtfromthepitsorriverbeds（calledasallinaggregate）aredirectlyused.Fineaggregate

SandandanyotheraggregateswhichpassthroughIS:

4.75mmsieveiscalledfineaggregate.Sandisbroughtfromlakes,pits,riversandsea-shores.（4）gandisthoroughlywashedsothatthereremainnoclayfilmsoverthesurfaceoftheaggregate.Itpreventsadhesionof

cementtotheaggregate.Clayandsiltarefinematerialswhichpassthrough75micronIS:

sieve.Clayandsiltmaterials（ifpresent）willincreasewatercontent.Dustisalsodetrimentalmaterialtoconcrete.Assuchthefineaggregatesshouldbefreefromdust,organicimpuritiesandsilts.Chlorides（presentinseashoresand）causeefflorescenceandrustingandcorrosionofreinforcementinstructuralconcrete.

Inordertopreparestrongconcrete,angulargrainedsand（havinggoodinterlockingproperty）isused.Roundgrainedparticlesofsandlackininterlockingproperty.

Inordertopreparetheconcretetohavegoodstrength,weatherresistanceanddurability,theaggregatesarecloselypacked.Forthisreason,thegradationofparticlesizesoftheaggregatesisofconsiderableimportance.

Gradingofaggregates

（5）Gradationofparticlesizesoftheaggregatevarywiththenatureandcourseofmaterialandtherequirementsinthisrespectdependuponthetypeofstructure.Theparticlesizesoffineandcoarseaggregatesareproperlygraded.Useofwellgradedaggregatesreducestheairvoids.Thecementfillsuptheairvoidsoffineaggregates.Thecementandsandbothtogetherfilluptheairvoidsofthecoarseaggregate.Thefinishing,workabilityanduniformityofconcreteareconsiderablyaffectedbythegradingoffineaggregates.

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