First, cement was added in layers to create texture, then combined with a “raw material” held together using a UV-protected epoxy resin.
The resin binds the material to itself and to the cement to create a continuous cylindrical form.
Materials they experimented with include rock salts, silica, sand and BB pellets, all in a range of colors, as well as coffee grounds.
Their main aim is for contrast, trying to find the right texture to complement the smoothness of the cement – or the right color to balance the texture of the raw material.
I think this is a very experimental method, and can be widely adapted to many different materials. So that you can get many different outcomes.