The application of thermal analysis to study the hydration behavior of tricalcium aluminate-gypsum in the presence of polycarboxylate-based superplasticizers

Highlights: • The hydration of C₃A and formation of monosulphate were evidently delayed by PCE. • The precipitate rate of C₃AH₆ in the presence of PCE was accelerated. • The morphology and size of ettringite crystals are changed by adsorption of PCE. • PCE play an important role on composition and microstructure of cement hydrates. The effect of polycarboxylate-based superplasticizers (PCE) on hydration behavior of tricalcium aluminate-gypsum system, which is a partial system of ordinary Portland cement, is investigated by means of isothermal calorimeter, thermal analysis and X-ray diffraction. The adsorption characteristics of PCE and morphology change of ettringite crystals upon PCE introduction are also examined by gel permeation chromatography and scanning electron microscope, respectively. Our results show that the initial hydration process and formation of crystalline monosulphate are significantly slowed down due to the presence of PCE. It is concluded that this retardation phenomenon is due to a stabilization effect induced by the adsorption of the PCE on ettringite precursor. Moreover, the morphology and size of ettringite crystals are found to be changed by the adsorption of PCE.