Hello - tried three times to compress these images enough but the website's still not happy, so I've just bunged them here: https://i.imgur.com/beNUohc.jpeg / https://i.imgur.com/Ke7qtNp.jpeg / https://i.imgur.com/ZMnlW4C.jpeg
Pretty straightforward question. the step going up to my Victorian tenement garden has historic damage on either side. Not causing any problems but I'd rather the rainwater didn't pool there. I know certain stone types need special treatment (eg lithomex for my sandstone coping wall), so I wanted to ask what is this stone (it seems to be layered - some kind of slate?)? And what's the best way to patch repair it in a way that won't cause problems?
My instinct was to just mix some Bostik general repair mortar with ~10mm aggregate and fill the holes (the pebbles because Bostik seems to crack when used by itself to join two different stones).
Though I should ask the experts before doing that though!
