Replacing closet bolts set in concrete

I am installing a new tile floor over concrete. The added height results in the closet bolts being too short to securely fasten the toilet again. The bolts are installed in the concrete. How can I remove these and install new longer bolts. There doesn't seem to be an easy way to get them out. Any help is appreciated.

Few wacks with a hammer ought to get them out. If not, hack saw them below the surface of the new floor. Don't let them fall into the pipe though! You should be able to place a new flange on top of the tile floor with new bolts. Do some searching of this forum and you'll find lots of posts about replacing closet flanges and changing floor heights.

Thanks,
Jason

Getting the old ones out will probably be a PITA! What I would try is to get them out as suggested, then using lead ferrels in the holes left. It's likely the holes will be too large for the ferrels, so you may need to use some hydralic cement to set them in, possible completely fill the holes with the cement then drill the holes for the ferrels after the cement has hardened. Use stainless steel screws into the ferrels to hold the flange. This is not super easy, but should be do-able.

Or you could throw down a repair ring like this,
Roto hammer some 1/4" holes in the concrete
and use concrete anchors.

bolts

If your only interested in the bolts, they make long closet bolts or did you mean bolts that are screwed into some sort of anchor?

flange

A proper installation has a flange fastened to the pipe, then the bolts slide into slots on the flange. If the bolts are into the concrete and there is no flange then it is a "handyman" installation, and you should do whatever is necessary to install them correctly.