My cat has been licking the mortar on the fireplace for weeks. Today, he put up the fight of his life to go outside, so he was out on a leash most of the day and licking the concrete. Concrete has lime & sea shells, so I'm wondering what he's needing..calcium? Lime? He doesn't seem to be feeling too well, so I will be taking him to the vet, but was looking for some input on what he might be trying to get into his system.