How best to refurbish the failed floor of a concrete pool

[Mike Conroy]

I live in Andalucia in Spain where summer temperatures can reach 35 ° C – 40 ° C (95 ° F - 105 °F).
I have a concrete pool 6m x 4m (20ft x 13ft), 170cm (5’6”) at deep end, of which 30cm (1ft) is below ground.
Originally painted the walls & floor are now covered with mosaic tiles.
The water leaches about 4cm (1½”) per day indicating that the pool is leaking 2cm – 3cm (1”) per day.
We have removed the mosaic floor tiles to reveal a substantial crack & some minor cracks. Along the line of the crack the concrete has failed & is like wet sand.
Elsewhere there are large areas where the tiles could be easily removed from the cement to reveal the presence of green algae.
So it would appear that the grout had become porous too.
I plan to refurbish the floor & to paint it.
Initially I will dig out the crack and re-fill with concrete, reinforced with rebars.
I’d like then to re-surface the floor & to seal it.
What would people recommend?
Any other thoughts?

[Teapot1]

Ok you seem on top of the issues. I would recommend stainless steel crack ties. Also the expanding cement mortars based around bentonite. Not sure what would be available to you but try looking for hydroplug.
I would also cover the entire base with a self levelling screed, Ardex K301 is one of the best.