Removing white cement spot - maru
Parked my car under construction are where the cement has not fully dried up. Was raining overnight and my car window and bodywork are now having some white stains caused by the cement.
How could I remove the white stain from the window and bodywork without scratching the surfaces.

Removing white cement spot - Dizzy {P}
You could try dabbing with a cloth soaked in a weak acid like vinegar then flushing off with water. If not, oxalic acid (from the chemist) would be a bit stronger and is sometimes used in diluted form to clean car bodywork.

These are only suggestions 'from the top of my head' and there may well be better ways to remove the stains.
Removing white cement spot - J Bonington Jagworth
That's what I would have said Dizzy. Or you could rub with half a lemon, even. Good idea to wash off any residue straight afterwards, though, followed by a good wax polish to prevent a repeat episode!
Removing White Cement Spots - Sooty Tailpipes
Jetwash?
Should come off OK, cement comes off easily when spread that thinly/
Removing white cement spot - Halmer
Have you managed to remove it maru?
Removing white cement spot - maru
I have finally removed it by using hardwax, similar to those of Autoglym Paint Renovator, and then followed by some soft wax to preserved back the paint work.

Thank you