Vanilla concrete powder should be able to be ran through a chemical bath / chemical reactor with water to make solid concrete. I think this recipe makes sense and would make building with concrete a tiny bit easier.

Using EnderIO tanks with water works quite fine. Just ensure you have enough water, and then it's just input-output with whatever method you like.

I think you make concrete from concrete powder in an Ender IO tank, which is super fast and power free.

I've always found using the EnderIo tank to make things inside it rather tedious as it doesn't always work properly and its not that fast. Plus I primarily use thermal tanks, so its not like i have them sitting around.

These reasons are why I recommended using a preexisting machine.

I can see the value in that; it might even make sense to have that just be part of GTCE itself. I believe there's a few different kinds of concrete added by mods in addition to vanilla though. We should look into this further.