Or just a few pounds of sugar when the concrete is wet. Concrete needs to be able to bond to the water molecules to cure, but dissolved sugar prevents that. So the concrete will never actually cure, and will crumble back into dust when it dries instead of turning solid. Anyone with a hardhat, safety vest, and work boots could blend into a large construction site long enough to lob a bag of sugar into a concrete mixer.

I’m not saying you should use it to oppose police stations, prisons, roadways immediately surrounding capitol buildings, etc from being built or repaired. But you could.