a fire - resistant composite slab , especially one that is composed of three layers , which has a central layer made of glued , inorganic expanded materials combined with inorganic fiber - containing fillers . outer layers in the form of slabs are provided on both sides of the central layer . these comprise at least two layers of glued expanded materials between which a continuous , flat reinforcement layer is provided . the fire - resistant composite slab can be used in constructing the interiors of buildings and ships .