Enhancement on fireproof performance of construction coatings using calcium sulfate whiskers prepared from wastewater

Abstract

This work is dealing with the fireproof performance of gypsum composite painting for fire passive protection in building construction. An efficient microwave-assisted method is adopted to fabricate high-crystalline CaSO4·2H2O whiskers from wastewater. The as-prepared CaSO4·2H2O whiskers display one-dimensional structure with a high aspect ratio of 40. The thermal resistive behavior of CaSO4− containing paints is investigated using thermo-gravimetric analyzer, differential scanning calorimetry, and direct flaming test (at 150, 570, and 1100 °C). The addition of CaSO4·2H2O whiskers not only improves the anti-flammability but also reduces the ignition temperature of construction painting. This result can be attributed to the fact that the heat transfer through the CaSO4-containing painting can be alleviated until the endothermic reaction steps [i.e., dehydration of gypsum (CaSO4·2H2O) and crystalline phase change of β-hemihydrated plaster] are totally completed. The burned fractions (including pyrogenation and carbonization) on CaSiO3 substrate are decreasing functions of the content of CaSO4·2H2O whiskers, proving that gypsum works as an insulator against heat transfer and flame spreading. Accordingly, the CaSO4·2H2O whiskers can be considered as an effective fire retardant additive for improving the fireproof ability of construction coatings.