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1、LawrenceBerkeleyNationalLaboratoryLawrenceBerkeleyNationalLaboratoryTitle:EffectsofcompositionandexposureonthesolarreflectanceofPortlandcementconcreteAuthor:Levinson,RonnenAkbari,HashemPublicationDate:12-21-2001PublicationInfo:LawrenceBerkeleyNationalLaborato
2、ryPermalink:http://escholarship.org/uc/item/5h77n60mKeywords:solarreflectancealbedoPortlandcementconcretepavementweatheringultravioletlightcondensationsoilingabrasionwettingcementaggregateAbstract:Increasingthesolarreflectance(albedo)ofapavedsurfacekeepsitcoo
3、lerinthesun,reducingconvectionofheatfrompavementtoairandtherebydecreasingtheambientairtemperature.SimulationsoftheinfluenceofpavementalbedoonairtemperatureinLosAngelespredictthatincreasingthealbedoof1,250km2ofpavementby0.25wouldsavecoolingenergyworth$15Myr-1,
4、andreducesmog-relatedmedicalandlost-workexpensesby$76Myr-1.Mostsidewalksandasmallfractionofroadsandparkingareasarepavedwithportlandcementconcrete,whichcanbemadequitereflectivethroughsuitablechoiceofcementandaggregate.Variationswithcompositionandenvironmentale
5、xposureofthealbedosofportlandcementconcretepavementswereinvestigatedthroughlaboratoryfabricationandexposureof32mixesofconcrete.Twenty-fourmixesyieldedsubstandard,"rough"concretesduetohigh,unmetaggregatewaterdemand.Thealbedosoftheremainingeight"smooth"concrete
6、mixesrangedfrom0.41to0.77(mean0.59).Simulatedweathering,soiling,andabrasioneachreducedaverageconcretealbedo(meandecreases0.06,0.05,and0.19,respectively),thoughsomesamplesbecameslightlymorereflectivethroughweatheringorsoiling.Simulatedrain(wetting)stronglydepr
7、essedthealbedosofconcretes(meandecrease0.23)untiltheirsurfacesweredried.Concretealbedogrewasthecementhydrationreactionprogressed(meanincrease0.08),butstabilizedwithinsixweeksofcasting.White-cementconcreteswereonaveragesignificantlymorereflectivethangray-cemen
8、tconcretes.Thealbedoofthemost-reflectivewhite-cementconcretewas0.18to0.39higherthanthatofthemost-reflectivegray-cementconcrete,dependingonstateofexposure.Concretealbedogenerallycorrelated
