Hydration kinetics of cementitious materials based on low-field NMR and isothermal calorimetry

The Krstulovic-Dabic (KD) hydration kinetic model is often used to study the hydration mechanism of cement-based materials. Based on this model, isothermal calorimetry is usually to study the hydration kinetics of cementitious materials, and the obtained data can describe the hydration process well. In this paper, low-field NMR was used to monitor the hydration process of cementitious materials, and the results were compared with that obtained by isothermal calorimetry. The results showed that KD model was also suitable for Low-field NMR. And the results of the low-field NMR were consistent with those of the isothermal calorimetry, both proving that the hydration stages of the PC and C3S were NG-I-D and NG-D, respectively. The difference was that low-field NMR displayed a faster hydration rate than isothermal calorimetry, which led to a shorter duration of D process. This phenomenon may be due to the fact that low-field NMR (1H in free water) and isothermal calorimetry (hydration heat) are based on different signal sources, and the water consumption rate is faster than heat variation rate in the early hydration period. In summary, low-field exhibits high effectiveness in characterizing the hydration kinetic process of cementitious materials.