Phase transformation and bloating behavior of CaMgSi2O6 glass-ceramics with ZrO2 nucleating agent using two-stage heat treatments were investigated as functions of annealing temperature. The specimens annealed below critical nucleation temperature (T-cn) and sintered at 950 degrees C exhibit significant bloating phenomena. Kinetic study of CaO-MgO-SiO2-ZrO2 (CMSZ) glasses annealed below T-cn reveals high activation energy of crystallization for the ZrO2 nucleation, and XRD refinement results show the least ZrO2 contents. The formations of fleeing oxygen and bloating are likely associated with high energy barrier of ZrO2 phase and zirconia dissolution in the CMSZ glass. Specimens annealed above the T-cn and sintered at 950 degrees C show significant reduction of activation energy of ZrO2 and enhanced densities. This work demonstrates that the bloating behavior of diopside glass-ceramics is attributed to the activation energy of nucleating agents. (C) 2017 Elsevier Ltd. All rights reserved.