What to mix with cement to make waterproof concrete?
#0183;#32;I''ve used waterproofing additives that mainly have PVA in them. The third from best is adding silicates to the mix to increase density, this helps but not that 70mm concrete bocks, with 10mm render (same as you''d put on any wall), and then a thin skim of pure cement slurry well worked onto the surface, and polished with a steel trowel.