Degradation Mechanisms of Early Strength for High-Fluidization Cement Mortar under Magnesium Sulfate Corrosion

Abstract

High-fluidization and early strength cement mortar (HECM) has been widely adopted in various fields of civil engineering. Due to the complexity of the engineering environment, sulfate corrosion cannot be ignored for the HECM. Although the effect of sulfate on the properties of the cement-based materials has been addressed, the degradation mechanisms of the HECM in the case of sulfate corrosion are not clear because of the distinct characteristics of the HECM (e.g., early strength and high fluidization) compared with conventional cement-based materials. Hence, considering the more complex corrosion process of magnesium sulfate, the early flexural and compressive strength of the HECM in the case of different magnesium sulfate concentrations and testing ages are investigated in this study. Moreover, the effects of magnesium sulfate concentrations and corrosion times on the microstructure and hydration products of the HECM are analyzed via a Scanning Electron Microscope (SEM) test, an X-ray diffraction (XRD) test, and a Differential Scanning Calorimeter (DSC) test. Finally, the influence mechanisms of the magnesium sulfate on the early strength formation of the HECM are analyzed to reveal the degradation mechanisms of the HECM.