To use flue gas desulfurization (FGD) gypsum and limestone as supplement of cement, conduction calorimetry was applied to
investigate the early hydration of ternary binder of calcium aluminate cement (CAC), Portland-limestone cement (PLC), and
FGD gypsum, supplemented with the determination of setting times and X-ray diffraction (XRD) analysis. Different exothermal
profiles were presented in two groups of pastes, in which one group (group A) sets the mass ratio of FGD gypsum/CAC at 0.25
and the other group (group B) sets the mass ratio of PLC/CAC at 0.25. Besides the two common exothermal peaks in cement hydration,
a third exothermal peak appears in the pastes with 5–15% FGD gypsum after gypsum is depleted. It is found that not PLC but
FGD gypsum plays the key role in such ternary binder where the reaction of ettringite formation dominates the hydration process.
PLC accelerates the hydration of ternary binder, which mainly attributes to the nucleating effect of fine limestone particles
and PC clinker. The modified hydration process and mechanism in this case is well visualized by the means of calorimetry and
it helps us to optimize such design of ternary cementitious material.