If you have kept a cat for period of time in your basement and cannot get the smell of urine out of the concrete floor, there are a number of remedies you can take.
There are a few solutions that you can buy at a retail store that are made specifically for the purpose of removing odors. If you are lucky enough to find one that works it should then be sealed with an oil based sealer.
The fact of the matter is it is very difficult to totally remove an odor such as this as it will continue to rise to the surface. Cleaning it with a retail cleaning product and then sealing it in is the recommendation of most professionals in the cleaning business. Once a concrete surface is sealed the likelihood of the smell leaking out is reduced greatly.
The best way to avoid this situation is to always have a litter box for any cat you keep in your basement. Most cats are good at using their litter boxes and will use them every time they go to the bathroom. If there were any accidents that happened it is best to clean up the mess as soon as possible to prevent it from embedding in the concrete to begin with. If it is too late to take preventative measures follow the steps here and repeat if necessary to get the very best results possible if you have cat urine smells coming from the concrete floor of your basement.