Having tried similar things, I cannot stress enough how much you want to be printing molds like this in TPU unless you really really want your mold to be permanently embedded in the concrete
@RegalPotoo @Wilshire good point. Release agents are used for casting concrete. They look to be oil and water mix so I’m guessing most plastics would be compatible.
Also has to be a clear path out for the print/concrete.
You can also print the object and use it to make a silicone mold, right? That doesn’t stick to concrete.