a method for protecting and for restoring structural strength and substance to a concrete , fluid containing or conducting structure deteriorated to the condition of removal of substance of the concrete by sulfuric acids and like corrosive material in contact therewith is described by positioning a relatively thin thermoplastic layer of polyvinyl chloride or polyethylene , injecting a substratum of epoxy foam , polyurethane foam , or a combination thereof between the thermoplastic layer and the deteriorated concrete , and welding the foam to the thermoplastic layer . the product of the process is described .