See Post #24...
Splicing rebar with gunpowder? When was this? 50 years ago?
To my knowledge, there is no rebar splicing done that way in the field. It is tied with tie wire. The theory is that the bond to the concrete creates a coupling between the two rebar ends. The ends have to be overlapped a certain minimal distance as specified in the bridge code.
Now, on a building with column and beam intersections, maybe there is an application, but I really don’t think this is done anymore on bridges.