OPTIMIZATION OF FIRE RETARDANCE FOR METAL STRUCTURES

The present study investigates foaming properties of fire-proof foam compositions based on water-dispersive materials. As the research showed, flame retardant coat based on ammonium carbonate (NH4)2CO3 (30 % of mass) and water-dispersive materials eliminated fire and produced uniform frothing with a slight crawling on the top. When ammonium carbonate was substituted by calcium sulfate dihydrate CaSÎ4·2H2O the coat blistered, did not flow from the surface of a sample but contracted exposing its edges, as a result the sample warmed up quickly. The concentration increase of calcium sulfate dihydrate to 20 % of mass eliminated contraction but led to splitting of the coat during the test. Ammonium chloride used as an additive with a concentration of 30 % of mass produced uniform frothing and eliminated combustion of the coat. The paper provides the findings on fire resistance of the steel samples protected with the flame retardants. The evaluation of the flame retardants efficiency was made on the steel samples and test equipment according to the state standard specification 30247.0–94 “Elements of building constructions. Fire-resistance test methods. General requirements”. It included time estimation from the beginning of the thermal action till the moment when the temperature on the unheated surface of the metal plate sample reached the limit point of 500 °Ñ. For some common grades of carbon and low-alloy steel this temperature approximately coincides with the temperature at which strength reduction and buckling of fabricated metals take place, i. e. fire endurance begins. As compared with a composition of the water-dispersive materials, the offered coat (water-dispersive material + 30 % of mass. of (NH4)2CO3) secures fabricated metals better under exposure to high temperatures. The primary fireproof effect is attained in the issue of transformation of a thin adsorption layer of the fire retardant to a highly porous heat insulating layer. The process is attended by intensive gas emission of incombustible low-molecular compounds, predominately carbon dioxide and water, which increase the foaming and thereby induce the reduction of the heat-transfer coefficient of the coat. When the additive of ammonium carbonate was substituted by calcium sulfate dihydrate, a specific effect was observed during the test. This effect was similar to the effect attained by the testing of the coat based on the water-dispersive material + 30 % of mass of (NH4)2CO3, i. e. the coat based on the water-dispersive material + 20 % mass. of CaSO4·2H2O provides high level of protection. The testing demonstrated that the coats with addition of ammonium chloride secure fabricated metals also reliably under exposure to high temperatures. The current paper provides the data on moisture permeability of the flame retardants and its performance attributes. During the research it was established that ammonium carbonate, calcium sulfate dihydrate and ammonium chloride are promising as additives to a composition of the water-dispersive materials used as the fire retardants for metal constructions.