Cracks in concrete

[Robertspaw]

Hi

My parents have a beach hut which is an old style stone and concrete construction with a solid concrete slab roof. There are a few cracks around the join between the walls and roof and a crack in the roof which is letting rain in.
Any ideas on what I can use to fill the gaps and make it water tight again? Could I use Rapid Setting Cement to fill the gaps and then perhaps put some flashing tape along the cracks? Would anything else work better?
Thanks in advance for any suggestions!

 

[nickjb]

I'd use a slurry of SBR and cement. It should flow into the crack a bit and stick to the surface.

 

[Robertspaw]

Thanks-very helpful. What mix between the sbr and concrete? Don't suppose you can buy it pre-mixed?