With the Hatton Garden burglary still in the news I started thinking about vault construction details, so I thought I'd start a new thread to discuss this. I don't intend to discuss how to break in, only how make to improvements.

At Hatton Garden and other burglaries the tool du jour seems to be the diamond-tipped core drill. Two ideas come to mind to thwart such an attack, or at least to slow it down. Aside from basic construction methods (high strength concrete, lots of rebar, possibly some deflector plates or hard steel bits thrown in), one idea is to mix into the concrete some sort of hard and sticky substance in the hope of seizing the core drill to stop it and to make extraction difficult. Capsules of something in between tree sap and amber come to mind. Also capsules of a fast setting epoxy but they need to be stable for at least the expected life of the building if not beyond. If used in great abundance they might impact the strength of the concrete, and after pouring, they might tend to float up in the concrete. I consider this an interesting but iffy idea that would require lots of experimentation.

Another anti-diamond-core-drill possibility is to mix in tungsten carbide cutting bits as used in machining. There are likely tons of broken/dulled inserts generated every day. Is there any sort of recycling being done? These could possibly be obtained in large quantities. Though diamond is harder than tungsten carbide, it might still slow down a drill significantly. This would require a fair amount of experimentation to determine the utility.

Most of today's high strength concrete is probably fairly resistant to the good old jackhammer. Plus it's slow and noisy and gets bogged down when the rebar is hit. But a friend suggested that mixing in a little bit of carbon fiber might make concrete more resistant. When a jackhammer breaks free a bit of the concrete at the surface it just likely falls away but with carbon fiber it might tend more to just stay in place, requiring extra work to break the fibers. I'm not too convinced but it's an interesting idea.

Any other thoughts, even if they aren't very economical or practical?