Concrete remnants on white acrylic steps

[KHeffner]

I have, about a little bit bigger than a half dollar, spot of concrete that the builders left on the white acrylic steps of our new pool, after they poured our decking. (They also left the pool water completely grey due to they washing their equipment in the water). They refuse to take responsibility for it and say that they didn't do it. We went into the pool and felt it and it is rough like sand paper.
They said it must be some kind of stain due to our water. Our water is darn near perfect thank to this forum.

Would anyone know of a safe way to begin to remove the concrete spot without doing major damage to the acrylic. I realize it may take time but it is an absolute eye sore in a beautiful pool
THANKS FOR ANY SUGGESTIONS!

 

[ouachita]

Take a putty knife and lay the blade flat against the step (imagine the concrete is a pancake and putty knife a spatula). Give it a good shove and it may pop right off. You could also GENTLY tap the putty knife with a hammer. My guess is the good shove will do it. It's probably not stuck that hard.

 

[ouachita]

Also you might put a layer or two of duct tape over the putty knife blade if you are worried it will scratch the steps.

 

[KHeffner]

Thanks for the suggestions. Will give it a try later.