You can also do a search for concrete dissolver on the net and you will find some commercially prepared mixes for concrete removal that are 100 biodegradable.
Temoving concrete splatter from siding.
If the concrete does splatter try to remove or clean it as quickly as possible before it hardens.
Test the acid solution before using it.
To prevent concrete from splattering onto other surfaces cover windows and siding before starting on any project that involves concrete.
Chip away small chunks of concrete from your siding with a putty knife.
How to remove dried concrete from vinyl siding.
Spray the window to help lubricate the glass and to prevent scratches.
Pour some sugar in a small bowl and add enough water to make a thin paste.
Wait five minutes for the sugar to soften the concrete.
How to remove concrete spatter from aluminum.
Mix one part acid with three parts water.
Dribble the sugar solution onto the concrete spatters or use a rubber spatula to smear it on.
How to remove concrete splatter from vinyl siding.
For areas with a large amount of splatter using a putty knife may.
Mix one part water and one part sugar and apply it to thick concrete splatters.
To improve the efficiency of concrete dissolvers consider adding water to area being addressed.
Old or hardened concrete splatter fill a spray bottle with water and mix about 2 to 3 drops of dish soap into it.