Fly ash-based lightweight geopolymer mortars for fire protection

The present study aims to investigate the use of geopolymer mortars as passive fire protection system for steel structures. Coal fly ashes were used as aluminosilicate source and perlite was employed as aggregate to obtain a lightweight system. In addition, a geopolymer mortar containing quartz aggregate was produced for comparison. The geopolymer mortars were applied on stainless steel plates and exposed to both, cellulosic and hydrocarbon standard fire curves, according to ISO 834-1 and EN 1363-2, respectively. Acoustic emission measurements were conducted to analyze cracking phenomena during the high temperature exposure. The resulting temperature-time curves showed that the investigated system is effective in retarding the temperature rise of the steel plates. When the cellulosic fire curve was applied, a 20 mm [0.79 in.] thick layer of lightweight geopolymer mortar protected the steel substrate from reaching the critical temperature of 500 ?C [932 ?F] for at least 30 minutes, avoiding the rapid decrease of its mechanical properties and thus representing an important safety measure against accidental fires. No spalling phenomena on heating were detected; however, significant cracking was observed on cooling.