Thaumasite form of sulfate attack in ettringite rich-ternary systems: Effects of limestone filler, etching solutions and exposure temperature

Abstract

This study aims to investigate the effect of limestone filler, sulfate concentration and temperature on the thaumasite sulfate attack (TSA) in Portland cement (PC)-calcium aluminate cement (CAC)-gypsum ternary system. The compressive strength of mortar was tested, while X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the deteriorated products. The results indicate that the ternary system with limestone filler is susceptible to TSA. The higher the limestone content, the higher the TSA is in systems with MgSO4 solution of less than 5%. When the limestone filler content is 10% or 20%, the sulfate attack is mainly presented as gypsum sulfate attack. When the concentration of MgSO4 solution increases, the corrosion is diminished. The ternary system exposed to low concentration MgSO4 solution of 5% is prone to form thaumasite. The lower the temperature, the more vulnerable the system is to TSA. The mortar at 5 °C under 5% MgSO4 solution is rarely damaged and thaumasite could easily be detected.

Keywords

• Sulfate attack
• Calcium aluminate cement
• Thaumasite
• Ettringite
• Temperature