It only took a few millimetres of rain overnight to undo all the hard work.
The flexible filler that was used to seal the many cracks needed a period of dry weather to harden off but the rain soaked the concrete pond both wetting the filling compound and adding moisture to the concrete. The filler became soft especially where it was quite thick. A couple of sections exposed to the previous afternoons sunshine were fine as they had dried and cured but the rest was a mush.
Starting all over again an angle sander with a wire brush attachment was used to clean out all the cracks. Then coarse sandpaper attached to the sander removed multiple layers of bituminous waterproofing exposed raw concrete edge around all the cracks.
With a clean working surface exposed Portland cement was mixed with a little water and a waterproofing cement additive then worked into the cracks and trowelled over forming a good binding patch. An overnight curing was all that was required. The beauty of cement is that a little moisture doesn't interfere with the setting process. Finally two coats of bituminous paint and 24 hours of dry weather allowed plenty of drying time.
Just waiting for a few showers to rinse the pond's surface before a final draining and refill.
Finally finished. Should have used cement in the first place.