Citric acid(CA)and chitosan(CS)were employed to modify magnesium oxychloride cement(MOC).Multiscale measurements were implemented to study the properties of the modified MOC pastes.Results show that the addition of CA...Citric acid(CA)and chitosan(CS)were employed to modify magnesium oxychloride cement(MOC).Multiscale measurements were implemented to study the properties of the modified MOC pastes.Results show that the addition of CA/CS significantly changes the content of each phase and the microstructure of phase 5.The single addition of CA can effectively increase the compressive strength of MOC after 7 d curing,while CS exerts no obvious effect on the compressive strength.As to the simultaneous addition of CA and CS,the compressive strength of MOC gradually decreases with the increasing content of CS.Interestingly,mixing CA and CS significantly enhances the water resistance of MOC and decreases the degradation rate of MOC in phosphate buffered solution,which can be ascribed to the low specific surface area of the plate-like crystals in the modified MOC and the reduction of pores in the structure.展开更多
Three types of electrodeposition,DC electrodeposition,low-frequency pulsed electrodeposition and high-frequency pulsed electrodeposition,were used to deposit cuprous oxide on the concrete surface to improve the antiba...Three types of electrodeposition,DC electrodeposition,low-frequency pulsed electrodeposition and high-frequency pulsed electrodeposition,were used to deposit cuprous oxide on the concrete surface to improve the antibacterial properties of concrete.The effects of pulse deposition frequency on the antibacterial property of concrete were studied using sulfate-reducing bacteria(SRB)and Escherichia coli(E.coli)as model bacteria.The bacterial concentration and the antibacterial rate were measured to evaluate the antibacterial performance of concrete.The effects of different deposition methods on the elemental content of copper and the amount of copper ions exuded were studied.XRD and SEM were used to analyze the microstructure of the deposited layers.The experimental results show that the concrete treated by electrodeposition exhibited good antibacterial properties against SRB and E.coli.The antibacterial effect of cuprous oxide deposited on concrete by pulse method was better than that by direct current(DC)method.The antibacterial rate of concrete was positively correlated with the exudation rate of copper ion.As the pulse frequency increased,the deposits content on the surface was increased with an accompanying improvement in the antibacterial property.Besides,the pulsed current had an indiscernible effect on the composition of the sediments,which were all mainly composed of Cu_(2)O,but the morphology of the Cu_(2)O differed greatly.Cubic octahedral cuprous oxide had better antibacterial properties with the highest copper ion leaching rate compared with cubic and spherical cuprous oxide.展开更多
The electrical conductivity of graphene/cement composite before and after carbonation was tested by a four-electrode method.The General Effective Media equation was adopted to fit the experiment results.EIS(electroche...The electrical conductivity of graphene/cement composite before and after carbonation was tested by a four-electrode method.The General Effective Media equation was adopted to fit the experiment results.EIS(electrochemical impedance spectroscopy)was employed to study the effect of carbonation on conductivity of graphene/cement composite.The mechanism was analyzed by SEM(scanning electron microscopy).It is revealed that electrical conductivity increases with increasing carbonation depth when the graphene content is less than 2.0%.In this case,the electrical conductivity of composite depends on cement matrix which can be enhanced by carbonation product through filling pores.When the graphene content exceeds 3.3%,the electrical conductivity decreases with increasing carbonation depth.The conductive path is mainly formed by graphene chains which can be broke by carbonation product.The GEM(General Effective Media)equation fits the experimental results well and can be used to calculate the electrical conductivity of graphene/cement composite after carbonation.展开更多
基金Funded by the National Natural Science Foundation of China(No.52071130)the Natural Science Foundation of Jiangsu Province(No.BK20211204)the Project of Outstanding Leading Talents in Gansu Province。
文摘Citric acid(CA)and chitosan(CS)were employed to modify magnesium oxychloride cement(MOC).Multiscale measurements were implemented to study the properties of the modified MOC pastes.Results show that the addition of CA/CS significantly changes the content of each phase and the microstructure of phase 5.The single addition of CA can effectively increase the compressive strength of MOC after 7 d curing,while CS exerts no obvious effect on the compressive strength.As to the simultaneous addition of CA and CS,the compressive strength of MOC gradually decreases with the increasing content of CS.Interestingly,mixing CA and CS significantly enhances the water resistance of MOC and decreases the degradation rate of MOC in phosphate buffered solution,which can be ascribed to the low specific surface area of the plate-like crystals in the modified MOC and the reduction of pores in the structure.
基金National Natural Science Foundation of China(Nos.52079048 and 52178203)the Natural Science Foundation of Jiangsu Province(BK20221503)+1 种基金the Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical EngineeringInstitute of Rock and Soil Mechanics,Chinese Academy of Sciences(Z020012)。
文摘Three types of electrodeposition,DC electrodeposition,low-frequency pulsed electrodeposition and high-frequency pulsed electrodeposition,were used to deposit cuprous oxide on the concrete surface to improve the antibacterial properties of concrete.The effects of pulse deposition frequency on the antibacterial property of concrete were studied using sulfate-reducing bacteria(SRB)and Escherichia coli(E.coli)as model bacteria.The bacterial concentration and the antibacterial rate were measured to evaluate the antibacterial performance of concrete.The effects of different deposition methods on the elemental content of copper and the amount of copper ions exuded were studied.XRD and SEM were used to analyze the microstructure of the deposited layers.The experimental results show that the concrete treated by electrodeposition exhibited good antibacterial properties against SRB and E.coli.The antibacterial effect of cuprous oxide deposited on concrete by pulse method was better than that by direct current(DC)method.The antibacterial rate of concrete was positively correlated with the exudation rate of copper ion.As the pulse frequency increased,the deposits content on the surface was increased with an accompanying improvement in the antibacterial property.Besides,the pulsed current had an indiscernible effect on the composition of the sediments,which were all mainly composed of Cu_(2)O,but the morphology of the Cu_(2)O differed greatly.Cubic octahedral cuprous oxide had better antibacterial properties with the highest copper ion leaching rate compared with cubic and spherical cuprous oxide.
基金Funded by the National Key R&D Program of China(No.2018YFC0406702)。
文摘The electrical conductivity of graphene/cement composite before and after carbonation was tested by a four-electrode method.The General Effective Media equation was adopted to fit the experiment results.EIS(electrochemical impedance spectroscopy)was employed to study the effect of carbonation on conductivity of graphene/cement composite.The mechanism was analyzed by SEM(scanning electron microscopy).It is revealed that electrical conductivity increases with increasing carbonation depth when the graphene content is less than 2.0%.In this case,the electrical conductivity of composite depends on cement matrix which can be enhanced by carbonation product through filling pores.When the graphene content exceeds 3.3%,the electrical conductivity decreases with increasing carbonation depth.The conductive path is mainly formed by graphene chains which can be broke by carbonation product.The GEM(General Effective Media)equation fits the experimental results well and can be used to calculate the electrical conductivity of graphene/cement composite after carbonation.
