Study on the Hydration Process of Fresh Cement Paste based on the Non-local Structural Derivative

Fresh cement paste (FCP) is widely used in construction engineering and 3D printing. Optimizing its performance is crucial for improving the construction quality and durability of building structures. However, there is still a lack of kinetic models for the particle diffusion behavior during the early hydration process of cement paste, necessitating the development of new theoretical tools to reveal its complex evolution mechanisms. This study establishes an ultrafast diffusion model based on the Riemann-Liouville non-local structural derivative theory to accurately characterize the hydration process of FCP. The numerical solution of the model is obtained using the finite difference method, and the corresponding mean square displacement (MSD) can be regarded as an integral form of the structural function. To validate the model, the Mittag-Leffler function is selected as the structural function, and nonlinear least-squares fitting is applied to the experimental MSD data of FCP hydration from 0 s~8 s and 0 s~18 s. A comparative analysis is conducted with the fractal derivative anomalous diffusion model and the non-local structural derivative model employing an exponential structural function. The results demonstrate that the non-local structural derivative ultrafast diffusion model can more accurately and effectively simulate the ultrafast diffusion behavior of cement particles. The model provides a new theoretical perspective for understanding the micromechanisms of viscoelastic evolution during the early hydration of FCP, as well as an effective mathematical tool for predicting and controlling the performance of concrete materials, showing significant theoretical value and engineering application prospects.