Formation and early hydration characteristics of C 2.75 B 1.25 A 3 $ in binary system of C 2.75 B 1.25 A 3 $-C 2 S

C 2.75 B 1.25 A 3 $ (2.75CaO•1.25BaO• 3Al 2 O 3 • SO 3 ) is one of the important minerals and it govern-directly the early-strength of belite-barium calcium sulphoaluminate cement. In this paper a binary system C 2.75 B 1.25 A 3 $-C 2 S is selected to investigate the formation of C 2.75 B 1.25 A 3 $. In the range of 1100 °C–1200 °C, the earlier formed C 2 S hinders the formation of C 2.75 B 1.25 A 3 $. On the contrary, when the temperature is in the range of 1200 °C–1350 °C, the initially formed C 2 S could provide a surface for the nucleation of C 2.75 B 1.25 A 3 $ and cut down the potential barrier (?Gk*) for the heterogeneous nucleation of C 2.75 B 1.25 A 3 $, which contributes to its formation. Moreover, at 1350 °C, the large amount of previously formed C 2 S benefits the extent of formation of C 2.75 B 1.25 A 3 $. The possible reason was that it could prevent sulfur evaporation. In early hydration age, AFm and AFt originating from C 2.75 B 1.25 A 3 $ hydration are found within 2 h and 12 h under 95% RH at 1 °C, respectively, whereas C 2 S is unhydrated at this moment.