Ok Healing,
Now that I can see the image, I believe it to be concrete with a gradient effect. (Like Clare explained)
1. I found a suitable concrete image that I liked.
2. I then desaturated the concrete by going to IMAGE > ADJUSTMENTS > DESATURATE.
I also adjusted the levels by going to IMAGE > ADJUSTMENTS > LEVELS. I made it much darker.
3. I then chose my Gradient tool.
I then clicked the first arrow on the left.
Which opened this window. I chose the foreground to transparent gradient. Make sure your foreground color is set to black.
4. Notice the image above of the toolbar with the three arrows. I set the Gradient to radial (second arrow) and then to reverse (third arrow).
I created a new layer above the concrete layer and I then pulled a Gradient from the inside out.
Note: The dark spots are where I added some extra dark brush strokes which I usually place on their own layer, ignore them.
Final image. Not quite like the original but you can see ONE way it could have been done!
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