Good work on the lighting conduit Jim.
The 'concrete' looks good enough to me, especially the area at the bottom of the picture, which I presume is 'outside'.
Bear in mind that it will look totally different once inside the hangar, under the shade of the roof and walls, and will look darker too.
If I was doing it, I'd leave it as it is, as far as colour and shade go, but soften the darker 'shadowed' areas of each slab, and then give the entire surface a very light, misted 'blow over' with a lighter shade, using a light grey with a touch of 'sandy light brown'.
Do this by using the airbrush at a distance - probably around 12 inches - and not aimed directly at the surface. Move the brush constantly and fairly quickly over the entire surface, to create a mist which will settle onto the 'concrete'.
Let it dry (should only take a minute or two), and then view the result as if it was inside the hangar, by making a 'tent' of paper or card over the top - or use the hangar structure itself if possible.
What might look very light 'in the open' will look very different in the shade.
All the above is if you require a
'concrete' finish, but remember that most hangar floors are painted, particularly these days, normally with an oil-resistant paint which is most commonly a light grey or off-white colour - the light grey being more suitable in model form, as it will look more realistic.
If you decide to have a 'painted' floor, then leave the 'outside' areas as it is, and just give an overall, even coat of the light grey to the hangar floor.
The pic below shows an example of the type of floor finish typical of virtually every hangar I've ever been in, with the odd exception, certainly in the UK and Europe, anyway.