It looks like the sort of undertaking that makes good sense in the 3rd world.
When I saw the paving stones made from plastic, I was thinking how slippery those would become once worn and wet. It occurred to me that a high proportion of the mix could be sand, thus greatly extending the use of the plastic, and making a stronger and more useful product.
I hope you explore this idea further.
I was also concerned about the lack of gloves or safety glasses around the molten plastic, the consequences could be catastrophic!