As far as I can tell (By sheer guessing and spending 20 minutes looking through NEI. Why on Earth is there almost no useful information about how to do things in this mod?), the way you create concrete is by combining one of the many recipes for concrete into a Mixer, of which the one I have is a Ceramic Mixing Bowl. This then gets you Concrete Dust.
Then you combine that with Water in a Mixer to get Wet Concrete, after that you then use a Dryer (of which I also have) to get the final Concrete. I did manage to get the Wet Concrete, but no matter how hard I tried, I could not get it out of the Ceramic Mixing Bowl. I tried using a bucket, nope. I tried looking for some kind of faucet in case that’s a thing for some reason, it does exist, but does nothing in this situation.