You can now start to remove the gum using an old putty knife. You should saw at the chewing gum until it starts to come loose, and then you can get rid of it fairly easily. You may need to repeat the first step a few times in order to allow the putty knife to get rid of all of it. If you are unlucky, you may find that the gum snaps off leaving you with a small piece of itself left on the concrete.

Step 1 - Dry up the Gum
Harden the wad of gum by either using a couple of ice cubes from the freezer or an aerosol freezing agent. This will hold the gum together helping to lift the gum in one or two strokes. The freezing agent can be purchased from most home improvement stores.

Step 2 - Scrape the Top
Use a sharp putty knife to scrape and chip away at the gum after it has become hard. You may have to repeat step 1 a couple of times to be successful. The majority of the gum should now be removed.

Step 3 - Wipe up the Rest
Spray any remaining gum with WD-40. Allow the lubricant to soak into the gum and the surrounding concrete area. After two or three minutes, use the putty knife to lift off the leftover gum.

Step 4 - Clean off the Concrete
In order to remove any gum which may be stuck in the tiny pores of your concrete, you should take a small pot of vinegar, and cover the area where the concrete was. You can then dissolve the gum by scrubbing it with a toothbrush. Leave for about 5 minutes, and then scrub over again using some water.