Rain damage when plastering

[Trevor]

It started raining (not heavily) 15 minutes before our contractors had finished plastering our pool (using grey quartzon).

The finish is therefore bad – you can see large discolored patches, which is where our contractor says the cement has been washed out of the plaster and down into the deep end. We’ve been using the pool and he has said that at the end of the season he will drain the pool and grind it slightly, which he is hopeful will address the discoloration. Failing that, it will be a re-plaster. I’m dubious about the grinding, but interested in any thoughts as to why we should not at least try it, e.g. affect on longevity, texture/roughness of the finish, etc.

Thanks

 

[onBalance]

A sanding or polishing can work very well, but yes, it is a difficult procedure. They should only have to remove or sand down a "paper thin" amount of plaster to make the surface smooth and non discolored. It can established a new, dense, and smooth surface. The thickness of plaster is usually about a half inch, more than enough to last a long time.
But I suggest that any kind of acid treatment is not a legitimate solution. That will only etch the surface, age the plaster, and will look worse six months later, and whoever is maintaining the water will be blamed instead and unfairly.