ARCACLEAR is a transparent waterproof membrane designed for this purpose. The area should be treated with ARCAMOSS beforehand. Arcaclear comes in kit form, each kit supplying the correct amount of products needed to treat 5m² or 10m². You would compose the kit by indicating the type of primer needed (in your case a porous primer), the finished look (the Arcaclear resin dries to a shiny finish - you should indicate mat if you do not want the shine) and the resistance you would need - the type of foot traffic the surface would have to bear (rare, domestic or public).
Don't hesitate to contact me if you have any questions at 020 31 51 31 20.