How do I achieve this effect of the imperfect cement wall on a flat surface in maya?
There's this newfangled thing called a "texture". You should look into it.
Normal map you make from actual concretw texture and then adding it to the bump map section of the attribute editor and setting it for tangent space normals.
The surface will still be flat but light will reflect off of it in different ways making it appear gouged and uneven
Normals. You can create a normal from a random texture online or you can throw it into zbrush and begin creating this effect and use that for your normal.
I'd recommend the zbrush idea because then you can make something that can be reused as a brush of sorts.
using normal-maps makes your wall great again
That looks a bit too imperfect tbh fam