It's gravel!

Here's an updated tiling gravel material created using photogrammetry in Reality Capture, with mesh repair and texture baking in Max. I used Knald for normals to height, Alchemist for tweaks and Artomatix for seam removal and texture mutation to extrapolate a 0.5m square source material into a 2m square seamless one. The gravel piles base geo was created using Gaea and Some vertex colour was baked in Max, to allow some per mesh colouration when the tiling material was dialed in. Look dev and rendering in Toolbag 4.

Gravel piles

Gravel piles

Texturing breakdown, the mound geometry was created in Max with a height map from Gaea

Moving light source, there is fencing geometry at the scene edges for reflections and shadows

Raytraced 4k render

Raytraced 4k render

Raytraced 4k render

Raytraced 4k render

Gravel is dull, so I added some colour

Gravel is dull, so I added some colour

Reference

Reference