Hello Everyone- I'm new to the forum. We have an early 80's vintage in-ground pool built by Sylvan. I believe it's concrete. We bought the house 6 years ago with the pool "as is", and used it for three years. The bottom was faded (blue) and rough on the feet. I thought it was painted and wearing off. Knew I'd have to do something down the line. Uncovered the pool two weeks ago, drained it, and was shocked to see it was stained brown, green and black and also looked like concrete was showing through in spots. After pressure washing, I'm wondering if it's not plaster instead of paint. Here is a pic of an area where I blasted away the "plaster" to reveal very rough concrete aggregate underneath, and a pic of a chunk of the "plaster".
Can anyone tell? The surface is rough but still bonding to the concrete (I have very few areas like the pic that I can blast through); if plaster, would an acid wash, patching, or sand blasting allow me to re-plaster without chipping it all out?