Effect of ternesite on the hydration and properties of calcium sulfoaluminate cement

Ternesite is an intermediate phase formed during clinkering of calcium sulfoaluminate (CSA) cement. This paper presents an experimental study on the feasibility of using ternesite as an additive of CSA cement in order to improve cement properties. Properties including setting time, mechanical strength, dimensional stability and hydration kinetics are investigated. The results indicated that the incorporation of ternesite can decrease the setting times and the strength development at early ages. The hydration of ternesite at later ages can increase the strength after 28 days of hydration, and 5% of ternesite is most favorable. The use of ternesite as an additive in CSA cement is harmless to the volume stability. The addition of ye'elimite to the pure ternesite promotes the hydration of ternesite and the formation of ettringite. XRD results show that the addition of ternesite can promote the formation of ettringite at later ages.