Influence of Sintering Procedure on Structure and Hydration Properties of Ternesite

The hydration activity of ternesite is crucial for the development of the mechanical properties of the new Belite-ye’elimite-ternesite cement. To explore a suitable sintering procedure for improving the hydration activity of ternesite, ternesite was synthesized by different sintering procedures with analytical reagents. The effect of sintering procedure on the microstructure, crystal structure, hydration activity and mechanical properties of ternesite was investigated by scanning electron microscopy, X-ray powder diffraction with Rietveld refinement, ²⁹Si solid-state nuclear magnetic resonance, comprehensive thermal analysis and isothermal calorimetry. The results show that ternesite grains obtained by a single-stage sintering process are irregular in shape and generally larger in size (~10 μm), while the shape of ternesite grains obtained by a two-stage sintering process are regular as granular, and the size of the grains decreases to approximately 5 μm. Air quenching can reduce the crystallinity of ternesite, thereby improving its early hydration activity and promoting the rapid development of its early mechanical properties. Among them, ternesite obtained by a single-stage sintering process and air quenching has the minimum degree of crystal structure development, but has the maximum early hydration activity and development strength. Ternesite obtained by cooling in a furnace has a higher crystallinity and a lower hydration activity in the early period, but its mechanical properties can develop rapidly in the middle and later periods.