Long-term performance of ferrite-rich calcium sulfoaluminate cement-based paste under seawater corrosion

Ferrite-rich calcium sulfoaluminate cement (FCSA) is widely used due to its characteristics of short setting time, high early strength, slight expansion and low CO2 emissions. In order to further study the long-term performance of FCSA under seawater environment, this study prepared a quaternary blend based on FCSA clinker, Ordinary Portland cement (OPC), anhydrite and limestone. Meanwhile, artificial seawater solutions were prepared by dissolving granular NaCl, MgSO4 and MgCl2 in deionized water. The long-term performance evolution of physical and mechanical characteristics such as mechanical properties, chloride content, hydration products and micro-structure property were investigated through uniaxial compression test, X-ray diffraction (XRD), thermogravimetric analysis (TG), mercury intrusion porosimeter (MIP) and other test methods by considering different salt concentrations of seawater and corrosion age. The results showed that the mass and expansion rate of corroded specimens increased logarithmically with the corrosion age. The quaternary blend could resist sulfate corrosion by absorbing it in seawater solution and promote the generation of ettringite. In addition, Friedel's salt was mainly generated by ion exchange between chloride and sulfate of monosulfoaluminate. The uniaxial compressive strength of all specimens showed a consistency of increasing first and then decreasing with corrosion age. Meanwhile, the corrosion resistance coefficient K of the specimens varied between 0.95 and 1.30 with the salt concentrations of seawater increasing. According to the mechanical behavior and micro-structure characteristics of the new quaternary blend, it’s indicated that the new cement-based material has adequate ability to resist seawater salt corrosion and has an excellent long-term stable performance.