Hey folks, my concrete driveway runs all the way down to the front wall of my house (besser block.) Where they meet, there's a 20mm gap:

It looks like the gap used to be filled with some kind of grout or mortar, which has now deteriorated and just crumbles away if you give it a poke.


Our block is below street level, so when it rains the water drains straight down the driveway towards the front of the house. There's a small lip just in front of the house that redirects the water around the side but it's very shallow so it overflows easily. We'll need to replace that with a proper drain and grate at some stage to minimise the chance of water hitting the house.
But in the mean time, how should I be filling this gap? I'm concerned that if it keeps filling with water we might end up with mould issues (or worse) under and around the slab.
I'm guessing some kind of grout, and then applying a sealant on top? Gap is 20mm wide and about 30mm deep.


Thanks in advance!