The base rock will become live rock as you cycle your tank. Within a few weeks it will be "live" and holding beneficial bacteria. Within a month or two the base rock will end up looking just like the live rock and you will barely be able to tell the difference.
Get that live rock in there as soon as you can, that can help jumpstart a cycle as well. In fact, get all the rock youre gonna want in there to save time. Youre cycling so might as well get all the rock "live" at once.