Dissolving large chunks of concrete is not an option so using a hammer, chisel away large chunks of the concrete to get closer to the surface you are trying to clean.
Use sandpaper in firm, strong vertical motion to remove bumps and ridges of excess concrete.
Clean the pressure sprayer thoroughly with hot water and mild detergent making sure it is dry before using.
Follow the manufacturer's instructions for using the Flo-Chem Concrete Off Plus Concrete Cleaner, Remover and Etcher and put it inside the pressure sprayer and apply a layer to the concrete you wish to remove for large surfaces.
Clean out the pressure sprayer again and fill with hot water and mild detergent and wash off the Flo-Chem once the alloted time as elapsed.