Abstract: An improved laminated panel construction for use in the construction of vaults in existing building structures, including outer laminae of steel sheeting with inner laminae of a dense hard wood such as oak, carbide abrasive, and concrete aggregate. The laminate is formed by bonding with epoxy adhesives in which the abrasive in particulate form has been suspended. Certain of the laminae are separated by lengths of metal forming a channel to form an interstice which is filled with the concrete aggregate after formation. The panels are formed with lap joints for assembly, the lap joints being covered with metal batten strips welded to the exposed surfaces of the outermost laminae.