my son has been laying a stone & brick patio for me and has had some trouble getting the extra (dried) concrete off the driveway and brickwork. appreciate recommendations.
Miriatic acid will do the trick. Find it at any pool supply store (about $2.00 a gallon). USING HEAVY RUBBER GLOVES, mix it about 50/50 with water and mop or sponge the entire affected area.