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
Due to the intrinsic nature of a heterogeneous and anisotropic microstructure of cement based materials and the small indentation size, the measured microhardness values are subject to considerable variability. This w...Due to the intrinsic nature of a heterogeneous and anisotropic microstructure of cement based materials and the small indentation size, the measured microhardness values are subject to considerable variability. This work presents an in-depth assessment of microhardness of hardened cement pastes（HCPs） from a statistical perspective. Hundreds of microhardness measurements were conducted on an HCP sample using a Vickers Microhardness Tester. The results showed that the microhardness measured from the HCP sample significantly scattered with a large standard deviation, varying from tens to hundreds. The data-set of microhardness values was not normally distributed but fit best with a three-parameter lognormal model. By using a statistical software, the probability density function of the microhardness distribution can be readily obtained. The arithmetic mean and its 95% confidence intervals of the measured microhardness values can be used to best represent the microhardness characteristics of HCPs.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the National Natural Science Foundation of China(Nos.51302191 and 51132010)
文摘Due to the intrinsic nature of a heterogeneous and anisotropic microstructure of cement based materials and the small indentation size, the measured microhardness values are subject to considerable variability. This work presents an in-depth assessment of microhardness of hardened cement pastes（HCPs） from a statistical perspective. Hundreds of microhardness measurements were conducted on an HCP sample using a Vickers Microhardness Tester. The results showed that the microhardness measured from the HCP sample significantly scattered with a large standard deviation, varying from tens to hundreds. The data-set of microhardness values was not normally distributed but fit best with a three-parameter lognormal model. By using a statistical software, the probability density function of the microhardness distribution can be readily obtained. The arithmetic mean and its 95% confidence intervals of the measured microhardness values can be used to best represent the microhardness characteristics of HCPs.
