An Efficient Open-Source Framework for Thermohygromechanical Phase-Field Simulation of Drying Damage Refractory Castables

Abstract

The water removal from refractory castables is a complex process involving heat and mass transport and thermohygromechanical stresses. In order to reduce the risk of explosive spalling by improving the heat-up curves, numerical models are critical to predict the castable behavior during drying. However, most of the existing models either neglect the thermomechanical stresses or consider them as an \textit{a posteriori} assessment of the likelihood of failure. The present work proposes an open-source thermohygromechanical phase-field model to simulate the drying of refractory castables and predict the occurrence of explosive spalling. The model is based on an adaptive two-scale time-stepping strategy that allows for a significant reduction of the computational cost associated with the simulation. The model was validated against literature results and qualitative comparisons with experimental data were carried out to assess its ability to predict the failure behavior of partially saturated porous media during heating. The numerical simulations were also applied to investigate the impact of different heating methods on the risk of failure during drying. It was found that even at the significantly lower heating rates typical of refractory castable drying - compared to the fire accidents that motivate most thermomechanical studies on concrete structures - thermomechanical stresses still play a significant role in the explosive spalling, a finding well established for concrete under fire but novel for refractory castables. As a consequence, it was also concluded that the use of heterogeneous heating methods can increase the likelihood of explosive spalling. Ultimately, feasible solutions to increase the drying efficiency and safety that are compatible with the industrial setting were proposed and a free, open-source implementation of the model is provided.