Properties evolution of calcium sulfoaluminate cement blended with ground granulated blast furnace slag suffered from sulfate attack

Abstract

In this work, sulfate resistance of calcium sulfoaluminate cement (CSAC) blended with ground granulated blast furnace slag (GGBFS) was studied. The mass change, compressive strength, corrosion resistance coefficient, relative dynamic elastic modulus and deformation of CSAC-GGBFS mortars exposed to 5% Na2SO4 solution for different time were monitored. At the same time, the mineral phases, pore structure and microstructure of hardened cement pastes after sulfate attack were determined using X-ray diffraction (XRD), thermal analysis, mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM). Results showed that the relative dynamic elastic modulus and compressive strength of the CSAC-GGBFS mortars increased continuously when the specimens were immersed in 5% Na2SO4 solution; besides, after 360 days of exposure, the compressive strength was 12% higher than the specimens cured in water. Meanwhile, the specimens displayed good dimensional stability after sulfate attack. What's more, no new mineral phases were found for the CSAC-GGBFS mixtures suffered from sulfate attack for 360 days, while the amount of AFt and C–S–H gels increased and the total porosity reduced. The CSAC-GGBFS mixtures showed excellent resistance to sulfate attack and can be applied in high sulfate environment.

Keywords

• Calcium sulfoaluminate cement
• Sulfate resistance
• Microstructure
• Durability