Oven dying kinetics and status of cement-based porous materials for in-lab microstructure investigation

Oven drying is one of the most commonly used methods to remove water confined in cement-based porous materials (CBPMs) for microstructural investigations. Water removal from porous solids can be governed by moisture diffusion, capillary flow and sorption-based mechanisms, which generate various drying models. Taking into account material types and water to cement ratios, the water removal kinetics and status of hardened cement pastes and mortars were investigated by oven drying at 60°C. Diffusion- and sorption-based drying kinetic models were revisited and employed to capture the drying profiles of CBPMs. The characteristics of drying profiles, model parameters and their relations to the pore structures of CBPMs were analysed. The results show that pore structure is a primary factor impacting drying kinetics and status. For dense porous solids, a long enough drying time is required to obtain a sufficiently dried status and for predicting the equilibrium moisture content by the models. Oven drying at moderate temperature can be an efficient drying method for removing water from a dense porous solid.