Development of a solid reaction kinetics gypsum dehydration model appropriate for CFD simulation of gypsum plasterboard wall assemblies exposed to fire

Gypsum plasterboard wall assemblies are extensively used as cladding material for walls, floors and ceilings, as well as a means for passive fire protection of timber structures. The good fire resistance characteristics of gypsum plasterboards are mainly owed to the gypsum “dehydration” process, occurring between 80 °C and 250 °C, where large quantities of energy are absorbed by evaporating water molecules, bound in the gypsum's crystal lattice. Aiming to enhance the prediction quality of numerical simulation tools, utilized to support the performance-based fire design of modern buildings, a gypsum dehydration numerical model is developed and validated. The model focuses on accurately describing the physical and chemical phenomena characterizing the gypsum dehydration process by employing a modelling approach based on solid reaction kinetics; temperature-dependent thermo-physical properties are also taken into account. The developed model is implemented in a Computational Fluid Dynamics code. Numerical results are validated by comparison to available temperature measurements obtained in a gypsum plasterboard wall assembly tested in a small-scale fire resistance furnace. Predictions of the developed model are found to agree reasonably well with the experimental data; a series of parametric studies is also performed aiming to investigate the effect of various modelling parameters.

► Fire resistance of gypsum plasterboards is owed to the gypsum dehydration process.
► A gypsum dehydration model is developed based on solid reaction kinetics.
► The new model is used for small-scale CFD simulations of gypsum plasterboards.
► Good agreement against measurements and improvement over alternative models.
► The new model allows quantification of variations in gypsum composition under fire.