The increasing importance of the ecologically minded production of building materials makes it necessary to develop reasonable alternatives to the CO2-intense production of ordinary Portland cement （OPC）. The develo...The increasing importance of the ecologically minded production of building materials makes it necessary to develop reasonable alternatives to the CO2-intense production of ordinary Portland cement （OPC）. The development of new or modified concrete is an important part of existing strategies to improve performance and minimize life-cycle costs. Therefore, we investigated carbonation resistance properties of sulphoaluminate cement （SAC） concrete incorporating layered double hydroxides （LDHs）. X-ray diffraction （XRD） and IR-spectroscopy were employed to characterize the component and structural changes of LDHs and cement paste before and after carbonation test. Carbonation resistance of concrete was experimentally evaluated. Finally, carbonation of Portland cement and SAC concrete was compared. The experimental results show that carbonation depth decreases remarkably with the addition of LDHs, especially the calcinated LDHs. Carbonation depth of SAC concrete is smaller than that of PC concrete regardless of curing time.展开更多
The sulfate ions immobilization behavior of calcined layered double hydroxides(CLDHs) in the hardened cement paste was investigated. The experimental results show that the sulfate ions in cement paste are immobilized ...The sulfate ions immobilization behavior of calcined layered double hydroxides(CLDHs) in the hardened cement paste was investigated. The experimental results show that the sulfate ions in cement paste are immobilized by CLDHs to reconstruct the layered structure and aggregate around CLDHs. The immobilization amount of sulfate ions by CLDHs reaches 4.74×10^-3 mol/g, while the increasing amount indicates non-linear relation with the addition of CLDHs. The incorporation of CLDHs decreases the amount of ettringite formed to limit the expansion of cement paste, which decays the sulfate reaction to enhance the sulfate resistance of concrete.展开更多
As a 3D micro-nano material, layered double hydroxides have been widely used in many fields, especially for reinforced composite materials. In this paper, Li Al-LDHs was obtained by a hydrothermal method. In order to ...As a 3D micro-nano material, layered double hydroxides have been widely used in many fields, especially for reinforced composite materials. In this paper, Li Al-LDHs was obtained by a hydrothermal method. In order to investigate the effects of Li Al-LDHs on the early hydration of calcium sulphoaluminate（CSA） cement paste, compressive strength, setting time and hydration heat were tested while X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FT-IR）, scaning electron microscopy（SEM） and differential scanning calorimetry（DSC） analysis were employed. The results indicated that Li Al-LDHs could significantly improve the early compressive strength and shorten the setting time of calcium sulphoaluminate cement paste with 3 wt% concentration. Besides, the hydration exothermic rate within 5h was accelerated with increasing Li Al-LDHs content. Moreover, the addition of Li Al-LDHs did not result in the formation of a new phase, but increased the quantity of hydration products providing higher compressive strength, shorter setting time and denser microstructure.展开更多
The purpose of this study is to apply the steel coated by cement paste to evaluate the corrosion inhibition of NO_(2)^(-) intercalated Mg-Al layered double hydroxides(LDHs),which was prepared by a conventional calcina...The purpose of this study is to apply the steel coated by cement paste to evaluate the corrosion inhibition of NO_(2)^(-) intercalated Mg-Al layered double hydroxides(LDHs),which was prepared by a conventional calcination-rehydration method.The chloride equilibrium isotherm,open-circuit potential(OCP)and electrochemical impedance spectroscopy(EIS)of steel in the saturated Ca(OH)_(2) solution contaminated by chloride ions were measured.The microstructures of as-obtained LDHs and cement paste containing the LDHs were observed by scanning electron microscope(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR)and mercury intrusion porosimetry(MIP).It is found that the technique using the steel coated by the cement paste layer containing the LDHs to represent the steel in real concrete can be applied to accurately evaluate the corrosion inhibition performance of NO_(2)^(-) intercalated LDHs in a short duration.The addition of NO_(2)^(-) intercalated Mg-Al LDHs can improve the absorption capacity of Cl^(-) and the anti-corrosion property of cement paste layer.The combination actions of the refinement of pore structure,uptake of chloride ions and release of inhibitive NO_(2)^(-) contribute to the better corrosion protection property of cement paste layer.Moreover,a schematic mechanism of chloride intrusion for the steel specimen with cement paste layer is developed.展开更多
基金Funded by the National Natural Science Foundation of China(No.NNSF-51272194)
文摘The increasing importance of the ecologically minded production of building materials makes it necessary to develop reasonable alternatives to the CO2-intense production of ordinary Portland cement （OPC）. The development of new or modified concrete is an important part of existing strategies to improve performance and minimize life-cycle costs. Therefore, we investigated carbonation resistance properties of sulphoaluminate cement （SAC） concrete incorporating layered double hydroxides （LDHs）. X-ray diffraction （XRD） and IR-spectroscopy were employed to characterize the component and structural changes of LDHs and cement paste before and after carbonation test. Carbonation resistance of concrete was experimentally evaluated. Finally, carbonation of Portland cement and SAC concrete was compared. The experimental results show that carbonation depth decreases remarkably with the addition of LDHs, especially the calcinated LDHs. Carbonation depth of SAC concrete is smaller than that of PC concrete regardless of curing time.
基金Funded by the National Natural Science Foundation of China(Nos.51508191,11502081,51502272,and 51608409)the Foundation from MWR Center for Levee Safety and Disease Prevention Research,State Key Laboratory of Silicates Materials for Architectures of Wuhan University of Technology(SYSJJ2014-3,SYSJJ2018-15)+1 种基金the Foundation from Engineering Research Center of Nano-Geomaterials of Ministry of Education,China University of Geosciences(NGM2018KF011)the Fundamental Research Funds for the Central Universities,China University of Geosciences
文摘The sulfate ions immobilization behavior of calcined layered double hydroxides(CLDHs) in the hardened cement paste was investigated. The experimental results show that the sulfate ions in cement paste are immobilized by CLDHs to reconstruct the layered structure and aggregate around CLDHs. The immobilization amount of sulfate ions by CLDHs reaches 4.74×10^-3 mol/g, while the increasing amount indicates non-linear relation with the addition of CLDHs. The incorporation of CLDHs decreases the amount of ettringite formed to limit the expansion of cement paste, which decays the sulfate reaction to enhance the sulfate resistance of concrete.
基金Funded by the National Natural Sciense Foundation of China(No.51272068)
文摘As a 3D micro-nano material, layered double hydroxides have been widely used in many fields, especially for reinforced composite materials. In this paper, Li Al-LDHs was obtained by a hydrothermal method. In order to investigate the effects of Li Al-LDHs on the early hydration of calcium sulphoaluminate（CSA） cement paste, compressive strength, setting time and hydration heat were tested while X-ray diffraction（XRD）, Fourier transform infrared spectroscopy（FT-IR）, scaning electron microscopy（SEM） and differential scanning calorimetry（DSC） analysis were employed. The results indicated that Li Al-LDHs could significantly improve the early compressive strength and shorten the setting time of calcium sulphoaluminate cement paste with 3 wt% concentration. Besides, the hydration exothermic rate within 5h was accelerated with increasing Li Al-LDHs content. Moreover, the addition of Li Al-LDHs did not result in the formation of a new phase, but increased the quantity of hydration products providing higher compressive strength, shorter setting time and denser microstructure.
基金the Natural Science Foundation of China(No.51478164)The Key Research&Development Plan of Jiangsu Province,China(No.BE2021704)。
文摘The purpose of this study is to apply the steel coated by cement paste to evaluate the corrosion inhibition of NO_(2)^(-) intercalated Mg-Al layered double hydroxides(LDHs),which was prepared by a conventional calcination-rehydration method.The chloride equilibrium isotherm,open-circuit potential(OCP)and electrochemical impedance spectroscopy(EIS)of steel in the saturated Ca(OH)_(2) solution contaminated by chloride ions were measured.The microstructures of as-obtained LDHs and cement paste containing the LDHs were observed by scanning electron microscope(SEM),X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR)and mercury intrusion porosimetry(MIP).It is found that the technique using the steel coated by the cement paste layer containing the LDHs to represent the steel in real concrete can be applied to accurately evaluate the corrosion inhibition performance of NO_(2)^(-) intercalated LDHs in a short duration.The addition of NO_(2)^(-) intercalated Mg-Al LDHs can improve the absorption capacity of Cl^(-) and the anti-corrosion property of cement paste layer.The combination actions of the refinement of pore structure,uptake of chloride ions and release of inhibitive NO_(2)^(-) contribute to the better corrosion protection property of cement paste layer.Moreover,a schematic mechanism of chloride intrusion for the steel specimen with cement paste layer is developed.
