Moisture and Heat Flow in Concrete Walls Exposed to Fire

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Abstract
Time‐dependent distributions for temperature and moisture content in a concrete wall subjected to fire are determined by a model of heat and mass transfer in porous media. Free‐water flow, bound‐water diffusion, gas‐phase flow, water‐vapor diffusion, and thermal energy are accounted for in the model. The governing transient differential equations are discretized by a control‐volume formulation reported by Patankar in 1980, and solved in time using a fully implicit scheme. Two different fire exposure curves (namely, standard curve according to ASTM E‐119 and a more realistic curve reported by Ellingwood in 1991) are employed in the analysis. The assessment of two simplified models, in which all pore water is assumed to evaporate at 100°C, is performed by comparing their predictions to the full analysis. For temperature and saturation, the time developments predicted by the two simplified models and by the full analysis present similar trends; however, the simplified models seem to be appropriate only for v...