Concrete requires either poor iron chunk or slag.

Slag is probabilistic waste product and scaling that without deadlocking on something else next to impossible.
The poor iron chunk however can only be crafted in a steam assembler which can't be beaconed or module'd.

I think the best solution would be to use "crafting-with-fluid" not "ei_steam-assembler" category, and patch the crafting categories for the steam assembler to include "crafting-with-fluid" (v0.5.7 doesn't have this)

There is something fun about having one part of the factory using this old technology.
But it would be great if we could get a steam chemical plant 2, just to be able to be beaconed.