My garage flat roof is surrounded by a low parapet with flat coping stones on top. A few years ago when the roof was replaced, the roofer sealed the coping stones, which were old and porous, with what looked like very thick, sticky grey paint with coarse fibres in it. This coating is starting to wear off in places and I would like to replace it but I have not been able to find anything that looks similar and the roofer is now unavailable. Can anyone suggest a name or brand name for this product?