Ah, the cement truck. That was one of my favourite segments. As I recall they shutdown a nearby highway for safety reasons and the crew was a mile away from the truck. Of course when they started, they were only supposed to use enough explosives to remove to break up the dried cement inside the drum...

The other one Sartaq mentioned about the ancient Chinese sapper warning system was fascinating too. That a device a thousand or two years old can detect something modern listening devices can't is just amazing.