I've been catching up on things with the forum and found this thread to be very interesting. Many years ago i worked in the flooring industry. The type of flooring our company did a lot of was expoxy resin coatings and floors. We used to do a lot of sculptured floors which had to handle high loads.

Granite was used as a high density filler for the hi loads. Silica sand was used for general use and mixing both together gave a happy medium for general use. Do'nt ask me for quantities as i can not remember but a company we did use was Flowcrete. We could order the stuff with fixed curing times.

Looking at the other thread in that link with the French build, i would have considered concreate with the thicknesses he was pouring. The advantage of epoxy resin is that you can get away with thinner sections (reinforce with mesh).

Things to think of are:

All fillers must be dry
Pea shingle makes an excelent cheap filler (wash and dry it before use)
Silica sand (paving gap filler from wickes)
This stuff shrinks
Always use mechanical mixing
Pouring too thick in one go is bad (add mesh to key pieces together), do it in a couple of pours before removing from the mould.
This stuff gets very hot so pour into moulds outside to avoid the nastys
Clean all items with thinners that are being sed within moulds
we worked to a max of 60mm for screeds in one go

if you use a release agent in the mould then you could use a gel coat to give you nice surface to paint afterwards.

Hope this helps