This is used today in the high security vault industry. Safes often include rubber pellets in the concrete pour between steel casing layers. Cutting into the s

This is used today in the high security vault industry. Safes often include rubber pellets in the concrete pour between steel casing layers. Cutting into the safe with a torch or plasma cutter will cause these rubber pellets to burn and fill the room with noxious odors and thick smoke. It doesn't necessarily increase the physical resistance to entry, but it makes the environment extraordinarily unpleasant.