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1、SECTIONFOURBUILDINGMATERIALSDavidJ.AkersCivilEngineer,SanDiego,CaliforniaThissectiondescribesthebasicmaterialsusedinbuildingconstructionanddis-cussestheircommonapplications.Astheworldspopulationincreasesandcon-sumesmoreofthenaturalresources,itisincumb
2、entuponthecivilengineertousebuildingmaterialsthatcontributetosustainingdevelopmentinsteadofsatisfyingonlytheshort-termneed.Materialselectionshouldincorporateanevaluationoftheamountofenergyrequiredtoproduceanddeliverthematerialtothebuildingsite.Thiscon
3、ceptofembodiedenergyisevolvingandvariable.Asanexample,inthePacificNorthwestlumberwouldhaveanembodiedenergyof1,butinthearidSouthwesttransportationraisesthevalueseveralpoints.Examplesofothermaterialsareconcrete(23),steel(46),andaluminum(80).Fordiscussion
4、pur-poses,materialsusedinsimilarapplicationsaregroupedanddiscussedinsequence,forexample,masonrymaterials,wood,metals,plastics,etc.CEMENTITIOUSMATERIALSCementitiousmaterialsincludethemanyproductsthataremixedwitheitherwaterorsomeotherliquidorbothtoforma
5、cementingpastethatmaybeformedormoldedwhileplasticbutwillsetintoarigidshape.Whensandisaddedtothepaste,mortarisformed.Acombinationofcoarseandfineaggregate(sand)addedtothepasteformsconcrete.4.1TYPESOFCEMENTITIOUSMATERIALSTherearemanyvarietiesofcementsandn
6、umerouswaysofclassification.Oneofthesimplestclassificationsisbythechemicalconstituentthatisresponsibleforthesettingorhardeningofthecement.Onthisbasis,thesilicateandaluminatecements,whereinthesettingagentsarecalciumsilicatesandaluminates,constitutethemos
7、timportantgroupofmoderncements.Includedinthisgrouparetheportland,alu-minous,andnaturalcements.4.14.2SECTIONFOURLimes,whereinthehardeningisduetotheconversionofhydroxidestocarbon-ates,wereformerlywidelyusedasthesolecementitiousmaterial,buttheirslowsetti
8、ngandhardeningarenotcompatiblewithmodernrequirements.Hence,theirprincipalfunctiontodayistoplasticizetheotherwiseharshcementsandaddresil-iencetomortarsandstuccoes.Useoflimesisbeneficialinthattheirslowsettingpromoteshealing,therecementingofhairli
