Its quite difficult to attain 90%-100% water proof property as most of the wastes which might possess this property are ASH in nature hence they are mostly water soluble.

I suggest you look out for waste materials with high pozzolanic characteristics, such as Rice Husk Ash, coal combustion fly ash (FA) (obtainable from Nigeria Railway Corporation), sewage sludge ash (SSA), granulated blast furnace slag (Dangote or Ewekoro cement company) and copala slag (mostly aluminium chippings - not very suitable); also check for other materials within this range.

I hope this helps alittle.

What is the application you have in mind? I've worked on some projects where we used evapotranspiration in combination with permeable materials to construct low infiltration caps. Not waterproof but under the right climatic conditions an effective barrier to infiltration.