a 35 pound package of black granulated pvc particles showed up at my doorstep on friday. it's exactly what i was hoping it would be. the particles are mostly triangular shaped, sized from no more than an 1/8" long all the way down to dust-sized particles.
tonight my wife helped make up some muck made out of the following ingredients:
2 parts granulated pvc
1 part ground oyster shell (rinsed)
1 part black landscaping colorado lace rock
1 part play sand
1 part quickcrete type 1 portland cement
~1 part water
we also mixed in a handfull of pasta shells after everything was mixed.
after seeing everything mixed together, i think i'm going to skip the oyster shell and increase the amout of pvc. the pvc particles look identical to the crushed oyster shells once they are grey and there is no chance of the pvc leaching organics that the oyster shells might leach over time.
the mixture is sitting in moist sand molds. i'll take pics once they've cured...hopefully in about a week.