This is my largest base which I sometimes use to show 2 jets (have a look at my Drakens on page 1 here), but in fact the concrete is more suitable for 1/32 or 1/35. A base 3 or 4 times bigger than this would need a lot of space on my expo table and it also needs to be stowed away and transported. And with markings I could only use it for this one purpose.
Yep, it's big but have a look at the following link:
I am using this stuff for my 1/48 scale airfield (well, what once upon a time should become my 1/48 scale airfield).
This stuff is the correct color, is fairly solid, fits very nicely together, can be put on any flat surface, and can be set-up/ stored away in a few minutes.