A composition which is applied to substrate surfaces to form a membrane to provide structural reinforcement thereto and prevent the release of gases and moisture from the substrate. The composition consists of polymer resin binders and gypsum. Further provided is a method for dividing the composition into two separate components in order to preclude premature setting up of the composition ingredients until applied to the substrate. The present invention is particularly useful for creating membranes on the exposed surfaces of newly excavated rocks in subterranean mine systems. The composition may also be used in the construction industry as coatings for sandwich panels, molding, duct-work, piping and cladding systems. It also is useful in traffic paint applications and other transportation industry safety coatings. In addition, the invention may be used in the manufacture of fiber reinforced composite structures and composite construction components.