A fractional kinetic model for drying of cement-based porous materials

ABSTRACT

In this work, we attempt to characterize the drying phenomena of cement-based porous materials (CBPMs) using a fractional kinetic model that is represented by a function for the kinetics of complex systems and characterized by a stretched exponential and/or power-law function with two parameters: the order index n and the fractional time index α. The fractional kinetic model recovers the classic Lewis and Page drying models as well as the pseudo first-order and pseudo second-order adsorption/desorption models with appropriate n and α values and boundary conditions. The fractional kinetic and classic drying models (i.e., the Lewis, Henderson and Pabis, Page, and logarithmic models) were used to interpret the experimental drying data for cement pastes and mortars. Rearrangement of the fractional kinetic correlation generates a linear log −log plot. The results showed that the values obtained using the fractional kinetic model and Page models were in better agreement with the experimental data than the values obtained using the other selected models. The results may also suggest that drying of CBPMs is more than a diffusion-controlled process.

KEYWORDS:

• Cement-based porous materials
• complex process
• drying
• fractional kinetics