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                     Gradientdomesticationandselectionofmineralizingmicroorganismssuitableforthe
                                        internalenvironmentofhydraulicconcrete
                                                                       2
                                                                                       1,2
                                   1,2
                                                           2
                                                 2
                    MENGYongdong ,XUXiaowei,DINGYi,WANGYu,CAIZhenglong ,TIANBin                    1,2
                                  (1.HubeiKeyLaboratoryofHydropowerEngineeringConstructionandManagement,
                                          ChinaThreeGorgesUniversity,Yichang 443002,China;
                        2.CollegeofHydraulicandEnvironmentEngineering,ChinaThreeGorgesUniversity,Yichang 443002,China)
                  Abstract:Theharshalkalineconditionswithintheinternalstructureofhydraulicconcreteconstraintheself - heal
                  ingefficacyofmicrobialconcrete.Thisstudyemploysagradientdomesticationmethodtoenhancethealkalinetoler
                  anceofmineralizedmicroorganisms ,selectingenhancedalkaliphilicmicroorganismsthatarewell - suitedtothepore
                  environmentofconcreteandpossessaheightenedcapacityforinducingmineralizationdeposition.Initially,under
                  highalkalineconditionsinlaboratory,theactivityandinducedmineralizationdepositionoffourBacillusspecies(B.
                  megaterium , B.cohnii, B.subtilis, and B.pasteurii)were compared.Microorganismsexhibiting superior
                  alkalineresistancewerepreliminarilyselected ,andanadaptivealkalinetolerancedomesticationprocesswascon
                  ducted.Subsequently,acomprehensiveinvestigationoftheimpactofdomesticatedmicroorganismsonconcreteme
                  chanicalproperties,capillarywaterabsorption,waterpermeability,andself - healingcapabilitywasundertaken.
                  ScanningelectronmicroscopyandX - raydiffractiontechniqueswereemployedforthecharacterizationofthemicro
                  scopicmorphologyandcompositionofmineralizedproducts.Theresultsindicatethat ,incomparisontoB.megate
                  rium,B.cohnii,andB.subtilis,B.pasteuriidemonstrateshigheractivityunderhighalkalineconditions.The
                  gradientdomesticationtechniquefurtherenhancestheactivityofB.pasteuriiinhighalkalineenvironments ,confir
                  mingthattheenhancedalkalineresistancethroughthismethodexhibitsmultigenerationalretentioncharacteristics.
                  Incomparisontothe28 - dayunmodifiedmicrobialsamples ,thecompressivestrengthofconcreteincorporatingdo
                  mesticatedmicroorganismsincreasedby16.59%,andwaterabsorptiondecreasedby37.74%.Additionally,the
                  maximumclosedcrackwidthwas0.57mm ,exceedingthe0.44mmoftheunmodifiedbacterialgroup.Comparedto
                  unmodifiedbacterialsamples ,thewaterpermeabilitycoefficientofdomesticatedbacterialsamplesdecreasedby
                  19.22% at28days.Thisresearchprovidesaviablestrategyforimprovingtheefficiencyofmicrobial - inducedcalci
                  umcarbonateprecipitationinconcrete.
                  Keywords:hydraulicconcrete;cracksself - repairing;mineralizedmicroorganisms;gradientdomestication;micro
                  analysis


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