Description of original award (Fiscal Year 2023, $290,289)
Gypsum plasterboards (Drywalls) are commonly used in building construction due to their fire-resistant properties. When exposed to fire, gypsum undergoes calcination, which leaves fire patterns on the gypsum board that can be used by fire investigators to determine the origin and cause of fires. Numerical prediction of gypsum calcination under fire exposure requires reliable gypsum thermo-chemistry models and material and thermophysical property data. A recently completed study by Eastern Kentucky University, funded by the National Institute of Justice, resulted in a variable heating rate thermo-chemistry model for a regular gypsum board. The study resulted in simplified correlations between the depth of calcination and incident heat flux for a regular gypsum board using experimental measurements and numerical predictions. However, these correlations are limited to regular gypsum boards. Different types of wall lining materials like moisture-resistant drywall, mold and mildew-resistant drywall, fire-resistant drywall, and sound-absorbing drywall are commonly used. These gypsum boards have different elements- like glass fibers, cellulose fiber, mineral wool, copper-based compounds, ammonium phosphate, and borates- added to them to get the desired characteristics. This could significantly change their behavior when exposed to fire. Failure to recognize the differences in the types of gypsum boards and their effect on fire patterns could mislead fire investigations. The proposed project aims to analyze different types of gypsum boards both macroscopically and microscopically. Variable heating rate thermo-chemistry models for different wall lining materials will be developed. Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC), and Fourier-Transform Infrared Spectroscopy (FTIR) will be used to characterize the calcination of gypsum boards. The developed models will be validated by comparing the temperature predictions with experimental measurements of internal temperature during the dehydration of gypsum boards. Controlled experiments will be conducted to investigate the effect of paint layers on gypsum calcination. A three-dimensional computational model will be developed and validated to analyze the effect of non-uniform heat flux. The sensitivity of each modeling parameter in the entire practical range will be assessed. Detailed microscopic and elemental analyses will be performed to understand the behavior of different types of gypsum boards exposed to fire. A user-friendly executable will be created to help fire investigators estimate the depth of calcination, based on either the known history of fire spread or the output of computational tools such as the Fire Dynamics Simulator. A database of material, thermo-physical, and thermo-chemical properties of different wall lining materials will be developed.
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