Preparation and Performance of Chitosan/Citric Acid Modified Magnesium Oxychloride Cement

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.