This is a 2 part question encompassing modeling and texturing but I thought I’d post it here as it’s mainly texture related. For now ignore the concrete texture I will need to change this as it’s not very high resolution, more of a placeholder.
(I beveled the sharp edges somewhat)
Firstly, I’m trying to get rough/uneven edges, for example around the hole edge in the concrete, I’m curious on your opinions how best to do this, how I have done it, and what I can improve on. I will need to do something similar with the pipe (a build up of limescale, chipping and general unevenness). At the moment it is a perfect cylinder which is obviously not natural with a pipe that has aged such as this. Assuming I’m on the right track with how I’m modeling this, what is the best way to then go about unwrapping, it usually creates distortions in the texture and unwraps in wildly unpredictable ways. I’m clearly doing something wrong.
Secondly, I want to add a separate “water stain” texture on the concrete under the pipe, and I’m wondering what is the best way to do this, edit it in Photoshop/GIMP and add the texture as a whole (this can’t be the best way)? Or do it in Blender? I’d prefer Blender but I’m still learning and I don’t know where to start on this (I was also hoping to use the same tactic to add some graffiti).
I hope I was clear, if not I’ll answer any questions you might have. Thanks for your help. 
