An example plasterboard includes a layer of hardened plaster having a first surface and an opposed second surface, a layer of polymer material having particles of one or more cementitiously-active substances mixed therein, and a liner between the first surface of the layer of hardened plaster and the layer of polymer material. Another example is a method of forming such a plasterboard. The method includes loading an extruder with the polymer material having the particles of one or more cementitiously active substances mixed therein, extruding the polymer material through a die to form the layer of polymer material on a surface of the liner, contacting with a layer of wet plaster material, the liner having the polymer material applied thereon such that the surface of the liner faces away from the wet plaster material, and drying the layer of wet plaster material to form the layer of hardened plaster.