Abstract: A concrete security structure such as a money safe, vault, or the like, is provided with unique burglar-proof qualities. The security structure includes a hardened concrete composition which possesses torch or high temperature resistance without flaking, spalling or exploding, and superior resistance to attack by means of burglary tools such as hammers, chisels, drills, cutting implements or the like. The security concrete is derived from a moldable uniform mixture which comprises granular temperature resistant aggregates, reinforcing filaments, an expansive cement and water. A method for making safes or vaults is provided by supplying a castable aqueous mixture of ingredients into a metallic shell, casing or mold and permitting the mixture to cure.