In a European military model magazine was once an article how to build crumbling (bombed) concrete. First the wall was scratched built with in perfect condition (I believe with plaster on plywood). Than he made a mold. Next fine sand was added inside of the mold with glue. The last step was casting the wall. Some lose sand was even picked up by the casting, which looked great. Some lose, twisted wires were placed inside the mold around the sand piles to become exposed rebar.
Unfortunately I don't have the magazine anymore and I never saw it on the internet.
