concrete mix for shed roof...not as mad as it sounds

[GA3587]

Ive got a concrete slab shed roof with a block work wall around the top.

When it rains, it fills with water.

There is a drainage point but the rise and fall points AWAY from it!

I want to lay a mix of concrete to create a valley and channel the water towards the drain.

What mix should I use?

ratios?

Im thinking of adding CEMENTONE integral water proofer?

Then painting ACrypol on top (when dry)


Any pointers advice on the mix ratio?

 

[tony1851]

1:2:4, with fine granite spar.
Mix some PVA glue with the mixing water, and also coat the top of the existing roof with the same mix immediately before applying the concrete.