Concrete is a porous material that soaks up stains and odors, making them difficult to remove. Cat urine is particularly unpleasant because of its strong smell, and if left to linger, the odds that another cat will choose that exact spot to eliminate in the future will increase greatly. Removing cat urine from concrete can be difficult, especially if the urine has already soaked into the concrete. However, with some work you can remove the cat urine odor, and protect your concrete from future stains and odors.
Mix together 1 quart of 3 percent hydrogen peroxide, a quarter cup of baking soda and 1 teaspoon of liquid soap in a non-metal container.
Decant this mixture into a plastic spray bottle. If you going to store this mixture, leave the cap slightly loose to allow air in and out of the bottle as hydrogen peroxide and baking soda will produce oxygen and increase the pressure inside the bottle.
Spray the concrete generously with the hydrogen peroxide mixture and allow it to dry. Wait two or three days to ensure that the concrete is completely dry.
Re-spray the concrete with the mixture if the odor remains. Repeat at least three times for optimal results.
Seal the area with a special concrete sealer available from most home improvement stores.