Abstract: Fireproofing compositions are provided. The compositions comprise a hydratable cementitious binder and polystyrene aggregate falling within particular particle size distribution limits. The compositions can also include an air entraining agent and a fibrous material. On addition of water, the compositions form settable, sprayable slurries which can be pumped to the point of application. The slurries are capable of spray application to steel structural members and adhere to the member in the slurried state and after setting. Excellent fire and heat protection is provided to the member despite the organic nature of the polystyrene aggregate.

Abstract: A method is provided whereby the setting time of a spray applied hydraulic cement-based fireproofing composition is decreased substantially while improving the yield of the composition. An acidic set accelerating agent is thus introduced into the composition effectively after conveyance through the system and in close proximity to the spray nozzle. At least about 0.5% of a basic material is provided which evolves a gas upon reaction with the accelerating agent. The invention also relates to the sprayable fireproofing compositions resulting from operation of the method.