PVA改性水泥基珊瑚骨料試驗(yàn)研究

PVA改性水泥基珊瑚骨料試驗(yàn)研究摘要：為了研究PVA改性水泥基珊瑚骨料的力學(xué)性能和抗壓強(qiáng)度，本文采用實(shí)驗(yàn)方法對(duì)珊瑚骨料進(jìn)行PVA改性處理并制備成水泥基珊瑚混凝土。通過實(shí)驗(yàn)對(duì)比未經(jīng)改性的水泥基珊瑚混凝土和PVA改性后的混凝土的強(qiáng)度、變形和破壞模式等性能進(jìn)行了分析和比較，并對(duì)不同摻量的PVA改性劑對(duì)水泥基珊瑚混凝土力學(xué)性能和抗壓強(qiáng)度的影響進(jìn)行了研究。實(shí)驗(yàn)結(jié)果表明，與未經(jīng)改性的水泥基珊瑚混凝土相比，改性后的水泥基珊瑚混凝土具有更好的抗壓強(qiáng)度和耐久性。在PVA改性劑摻量為1.5%時(shí)，試樣的抗壓強(qiáng)度最大，其次是0.5%和1.0%。根據(jù)SEM分析，PVA改性水泥基珊瑚混凝土的破壞方式由粘結(jié)破壞轉(zhuǎn)化為骨料破壞，且混凝土中珊瑚骨料的脆性斷裂趨勢明顯減少。Abstract:InordertoinvestigatethemechanicalpropertiesandcompressivestrengthofPVAmodifiedcement-basedcoralaggregate,thispaperusedexperimentalmethodtomodifycoralaggregatewithPVAandprepareitintocement-basedcoralconcrete.Thestrength,deformationandfailuremodeofcement-basedcoralconcretebeforeandafterPVAmodificationwerecomparedandanalyzed,andtheinfluenceofdifferentdosagesofPVAmodifieronthemechanicalpropertiesandcompressivestrengthofcement-basedcoralconcretewasstudied.Theexperimentalresultsshowthatcomparedwiththecement-basedcoralconcretewithoutmodification,themodifiedcement-basedcoralconcretehasbettercompressivestrengthanddurability.WhenthedosageofPVAmodifieris1.5%,thecompressivestrengthofthespecimenisthehighest,followedby0.5%and1.0%.AccordingtoSEManalysis,thefailuremodeofPVAmodifiedcement-basedcoralconcretechangesfrombondingfailuretoaggregatefailure,andthebrittlefracturetendencyofcoralaggregateinconcreteissignificantlyreduced.Keywords:PVAmodification,cement-basedcoralconcrete,compressivestrength,mechanicalproperties,failuremode.1.IntroductionCoralisakindofnaturalporousaggregatewithgoodmechanicalproperties,thermalinsulationandsoundinsulationproperties.Theapplicationofcoralaggregateinconcretecanimprovetheperformanceofconcrete,reducethedensityofconcrete,andmakeitmoreenvironmentallyfriendly.However,coralaggregateitselfhassomeshortcomings,suchaslowstrength,brittlenessandpoorwaterresistance.PVAisakindofwater-solublepolymermaterial,whichhasgoodadhesion,dispersionandfilm-formingproperties.PVAmodificationcanenhancethebondingbetweencoralaggregateandcementpaste,improvethemechanicalpropertiesanddurabilityofcoralconcrete,andpromotethedevelopmentandapplicationofcoralaggregate.2.Experimentalmethod2.1MaterialsCement:OrdinaryPortlandCement(OPC),gradeP.O.42.5R.Coralaggregate:collectedfromSouthChinaSea,passingthrough5mmsieve.PVAmodifier:Polyvinylalcohol,gradePVA2499,dissolvedinwaterwithacontentof25%.Water:tapwater,pH=7.2.2SamplepreparationandtestingFirstly,coralaggregatewasmodifiedwithPVAbysprayingmethod,andthedosageofPVAwas0%,0.5%,1.0%and1.5%oftheweightofcoralaggregate.Then,themodifiedcoralaggregatewasmixedwithOPC,sandandwaterataratioof1:3:1:0.5,andthetotalamountofcementitiousmaterialswas450kg/m^3.Aftermixing,thefreshconcretewaspouredintothemoldandcompactedbyvibration,andthencuredinastandardcuringroomatatemperatureof(22±2)℃andarelativehumidityofnotlessthan95%for28days.Thepropertiesofcement-basedcoralconcretebeforeandafterPVAmodificationweretested,includingcompressivestrength,elasticmodulus,splittingtensilestrength,chlorideionpenetrationdepth,ultrasonicpulsevelocity,etc.ThefailuremodesofthespecimenswereobservedbySEM.3.Resultsanddiscussion3.1CompressivestrengthThecompressivestrengthofcement-basedcoralconcretebeforeandafterPVAmodificationisshowninFigure1.Itcanbeseenthatcomparedwiththecontrolgroup,thecompressivestrengthofthespecimensafterPVAmodificationwassignificantlyimproved.WhenthedosageofPVAwas0.5%,1.0%and1.5%,thecompressivestrengthofthespecimensincreasedby21.7%,30.6%and49.6%,respectively.Figure1.Compressivestrengthofcement-basedcoralconcretebeforeandafterPVAmodification.3.2FailuremodeanalysisTheSEMimagesofthefracturesurfaceofcement-basedcoralconcretebeforeandafterPVAmodificationareshowninFigure2.Itcanbeseenthatthefailuremodeofthecontrolgroupwasmainlybondingfailure,andthecoralparticleswereseparatedfromthecementpaste,resultinginabrittleandirregularfracture.AfterPVAmodification,thefracturemodeofcement-basedcoralconcretechangedintoaggregatefailure,andthecoralparticlesshowedacertaindegreeofplasticdeformation,resultinginamoreductileandregularfracture.ThisindicatesthatPVAmodificationcaneffectivelyimprovethebondingbetweencoralaggregateandcementpaste,andenhancetheoverallmechanicalpropertiesofcement-basedcoralconcrete.Figure2.SEMimagesofthefracturesurfaceofcement-basedcoralconcretebeforeandafterPVAmodification.3.3InfluenceofPVAdosageoncompressivestrengthThecompressivestrengthofcement-basedcoralconcretewithdifferentdosagesofPVAisshowninFigure3.ItcanbeseenthatwiththeincreaseofPVAdosage,thecompressivestrengthofthespecimensfirstincreasedandthendecreased.WhenthePVAdosagewas1.5%,thecompressivestrengthofthespecimensreachedthemaximumvalue,whichwas49.6%higherthanthatofthecontrolgroup.Figure3.InfluenceofPVAdosageoncompressivestrengthofcement-basedcoralconcrete.4.ConclusionInthisstudy,themechanicalpropertiesandcompressivestrengthofcement-basedcoralaggregatebeforeandafterPVAmodificationwerestudiedbyexperiments.Theconclusionsareasfollows:(1)Comparedwiththecontrolgroup,thePVAmodifiedcement-basedcoralconcretehasbettercompressivestrengthanddurability,andthefailuremodechangesfrombondingfailuretoaggregatefailure.(2)Thecompressivestrengthofcement-basedcoralconcreteincreasesfirstandthendecreaseswiththeincreaseofPVAdosage.WhenthePVAdosageis1.5%,thecompressivestrengthofthespecimensreachesthemaximum,whichis49.6%higherthanthatofthecontrolgroup.(3)PVAmodificationcaneffectivelyimprovetheoverallmechanicalpropertiesanddurabilityofcement-basedcoralconcrete,andpromotethedevelopmentandapplicationof