Alex has done everything she can to try and remove it and has been unsuccessful. My fear is that it is grout. I need your help with these items please. I'm not sure we should have people grouting the can't clean them up after themselves. While I know it is impossible for you to control this, we need to come up with a solution before we permanently damage things if we haven't already. Grout can cause such damage and in some cases is not reversible.
On the far east end of the metal trough drain cover closer to our breakroom, there's a big white spill on the pavers and the drain cover. See photo.